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The scheduler IPI does not need the full interrupt entry handling logic
when the entry is from kernel mode. Use IDTENTRY_SYSVEC_SIMPLE and spare
all the overhead.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20200521202119.835425642@linutronix.de
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Convert SMP system vectors to IDTENTRY_SYSVEC:
- Implement the C entry point with DEFINE_IDTENTRY_SYSVEC
- Emit the ASM stub with DECLARE_IDTENTRY_SYSVEC
- Remove the ASM idtentries in 64-bit
- Remove the BUILD_INTERRUPT entries in 32-bit
- Remove the old prototypes
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20200521202119.372234635@linutronix.de
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Move it where it belongs. That allows to keep all the shorthand logic in
one place.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190722105220.677835995@linutronix.de
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To support IPI shorthands wrap invocations of apic->send_IPI_allbutself()
in a helper function, so the static key controlling the shorthand mode is
only in one place.
Fixup all callers.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20190722105220.492691679@linutronix.de
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A reboot request sends an IPI via the reboot vector and waits for all other
CPUs to stop. If one or more CPUs are in critical regions with interrupts
disabled then the IPI is not handled on those CPUs and the shutdown hangs
if native_stop_other_cpus() is called with the wait argument set.
Such a situation can happen when one CPU was stopped within a lock held
section and another CPU is trying to acquire that lock with interrupts
disabled. There are other scenarios which can cause such a lockup as well.
In theory the shutdown should be attempted by an NMI IPI after the timeout
period elapsed. Though the wait loop after sending the reboot vector IPI
prevents this. It checks the wait request argument and the timeout. If wait
is set, which is true for sys_reboot() then it won't fall through to the
NMI shutdown method after the timeout period has finished.
This was an oversight when the NMI shutdown mechanism was added to handle
the 'reboot IPI is not working' situation. The mechanism was added to deal
with stuck panic shutdowns, which do not have the wait request set, so the
'wait request' case was probably not considered.
Remove the wait check from the post reboot vector IPI wait loop and enforce
that the wait loop in the NMI fallback path is invoked even if NMI IPIs are
disabled or the registration of the NMI handler fails. That second wait
loop will then hang if not all CPUs shutdown and the wait argument is set.
[ tglx: Avoid the hard to parse line break in the NMI fallback path,
add comments and massage the changelog ]
Fixes: 7d007d21e539 ("x86/reboot: Use NMI to assist in shutting down if IRQ fails")
Signed-off-by: Grzegorz Halat <ghalat@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Don Zickus <dzickus@redhat.com>
Link: https://lkml.kernel.org/r/20190628122813.15500-1-ghalat@redhat.com
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x96 apic updates from Thomas Gleixner:
"Updates for the x86 APIC interrupt handling and APIC timer:
- Fix a long standing issue with spurious interrupts which was caused
by the big vector management rework a few years ago. Robert Hodaszi
provided finally enough debug data and an excellent initial failure
analysis which allowed to understand the underlying issues.
This contains a change to the core interrupt management code which
is required to handle this correctly for the APIC/IO_APIC. The core
changes are NOOPs for most architectures except ARM64. ARM64 is not
impacted by the change as confirmed by Marc Zyngier.
- Newer systems allow to disable the PIT clock for power saving
causing panic in the timer interrupt delivery check of the IO/APIC
when the HPET timer is not enabled either. While the clock could be
turned on this would cause an endless whack a mole game to chase
the proper register in each affected chipset.
These systems provide the relevant frequencies for TSC, CPU and the
local APIC timer via CPUID and/or MSRs, which allows to avoid the
PIT/HPET based calibration. As the calibration code is the only
usage of the legacy timers on modern systems and is skipped anyway
when the frequencies are known already, there is no point in
setting up the PIT and actually checking for the interrupt delivery
via IO/APIC.
To achieve this on a wide variety of platforms, the CPUID/MSR based
frequency readout has been made more robust, which also allowed to
remove quite some workarounds which turned out to be not longer
required. Thanks to Daniel Drake for analysis, patches and
verification"
* 'x86-apic-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/irq: Seperate unused system vectors from spurious entry again
x86/irq: Handle spurious interrupt after shutdown gracefully
x86/ioapic: Implement irq_get_irqchip_state() callback
genirq: Add optional hardware synchronization for shutdown
genirq: Fix misleading synchronize_irq() documentation
genirq: Delay deactivation in free_irq()
x86/timer: Skip PIT initialization on modern chipsets
x86/apic: Use non-atomic operations when possible
x86/apic: Make apic_bsp_setup() static
x86/tsc: Set LAPIC timer period to crystal clock frequency
x86/apic: Rename 'lapic_timer_frequency' to 'lapic_timer_period'
x86/tsc: Use CPUID.0x16 to calculate missing crystal frequency
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Using __clear_bit() and __cpumask_clear_cpu() is more efficient than using
their atomic counterparts.
Use them when atomicity is not needed, such as when manipulating bitmasks
that are on the stack.
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lkml.kernel.org/r/20190613064813.8102-10-namit@vmware.com
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Based on 1 normalized pattern(s):
this code is released under the gnu general public license version 2
or later
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 3 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Richard Fontana <rfontana@redhat.com>
Reviewed-by: Armijn Hemel <armijn@tjaldur.nl>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190520075211.232210963@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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The last missing piece to having vmx_l1d_flush() take interrupts after
VMEXIT into account is to set the kvm_cpu_l1tf_flush_l1d per-cpu flag on
irq entry.
Issue calls to kvm_set_cpu_l1tf_flush_l1d() from entering_irq(),
ipi_entering_ack_irq(), smp_reschedule_interrupt() and
uv_bau_message_interrupt().
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Nicolai Stange <nstange@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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The pagefault and the resched IPI handler are the only ones where it is
worth to optimize the code further in case tracepoints are disabled. But it
makes no sense to have a single static key for both.
Seperate the static keys so the facilities are handled seperately.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170828064957.536699116@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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It's worth to avoid the extra irq_enter()/irq_exit() pair in the case that
the reschedule interrupt tracepoints are disabled.
Use the static key which indicates that exception tracing is enabled. For
now this key is global. It will be optimized in a later step.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170828064957.299808677@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Two NOP5s are really a good tradeoff vs. the unholy IDT switching mess,
which duplicates code all over the place. The rescheduling interrupt gets
optimized in a later step.
Make the ordering of function call and statistics increment the same as in
other places. Calculate stats first, then do the function call.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170828064957.222101344@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 boot updates from Ingo Molnar:
"The biggest changes in this cycle were:
- reworking of the e820 code: separate in-kernel and boot-ABI data
structures and apply a whole range of cleanups to the kernel side.
No change in functionality.
- enable KASLR by default: it's used by all major distros and it's
out of the experimental stage as well.
- ... misc fixes and cleanups"
* 'x86-boot-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (63 commits)
x86/KASLR: Fix kexec kernel boot crash when KASLR randomization fails
x86/reboot: Turn off KVM when halting a CPU
x86/boot: Fix BSS corruption/overwrite bug in early x86 kernel startup
x86: Enable KASLR by default
boot/param: Move next_arg() function to lib/cmdline.c for later reuse
x86/boot: Fix Sparse warning by including required header file
x86/boot/64: Rename start_cpu()
x86/xen: Update e820 table handling to the new core x86 E820 code
x86/boot: Fix pr_debug() API braindamage
xen, x86/headers: Add <linux/device.h> dependency to <asm/xen/page.h>
x86/boot/e820: Simplify e820__update_table()
x86/boot/e820: Separate the E820 ABI structures from the in-kernel structures
x86/boot/e820: Fix and clean up e820_type switch() statements
x86/boot/e820: Rename the remaining E820 APIs to the e820__*() prefix
x86/boot/e820: Remove unnecessary #include's
x86/boot/e820: Rename e820_mark_nosave_regions() to e820__register_nosave_regions()
x86/boot/e820: Rename e820_reserve_resources*() to e820__reserve_resources*()
x86/boot/e820: Use bool in query APIs
x86/boot/e820: Document e820__reserve_setup_data()
x86/boot/e820: Clean up __e820__update_table() et al
...
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Modify the reschedule warning to output the offline CPU number and
use a better debug message.
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1492518305-3808-1-git-send-email-prarit@redhat.com
[ Tweaked the warning message. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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A CPU in VMX root mode will ignore INIT signals and will fail to bring
up the APs after reboot. Therefore, on a panic we disable VMX on all
CPUs before rebooting or triggering kdump.
Do this when halting the machine as well, in case a firmware-level reboot
does not perform a cold reset for all processors. Without doing this,
rebooting the host may hang.
Signed-off-by: Tiantian Feng <fengtiantian@huawei.com>
Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
[ Rewritten commit message. ]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm@vger.kernel.org
Link: http://lkml.kernel.org/r/20170419161839.30550-1-pbonzini@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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This patch adds the __irq_entry annotation to the default x86
platform IRQ handlers. ftrace's function_graph tracer uses the
__irq_entry annotation to notify the entry and return of IRQ
handlers.
For example, before the patch:
354549.667252 | 3) d..1 | default_idle_call() {
354549.667252 | 3) d..1 | arch_cpu_idle() {
354549.667253 | 3) d..1 | default_idle() {
354549.696886 | 3) d..1 | smp_trace_reschedule_interrupt() {
354549.696886 | 3) d..1 | irq_enter() {
354549.696886 | 3) d..1 | rcu_irq_enter() {
After the patch:
366416.254476 | 3) d..1 | arch_cpu_idle() {
366416.254476 | 3) d..1 | default_idle() {
366416.261566 | 3) d..1 ==========> |
366416.261566 | 3) d..1 | smp_trace_reschedule_interrupt() {
366416.261566 | 3) d..1 | irq_enter() {
366416.261566 | 3) d..1 | rcu_irq_enter() {
KASAN also uses this annotation. The smp_apic_timer_interrupt()
was already annotated.
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Claudio Fontana <claudio.fontana@huawei.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Dou Liyang <douly.fnst@cn.fujitsu.com>
Cc: Gu Zheng <guz.fnst@cn.fujitsu.com>
Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicolai Stange <nicstange@gmail.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Cc: linux-edac@vger.kernel.org
Link: http://lkml.kernel.org/r/059fdf437c2f0c09b13c18c8fe4e69999d3ffe69.1483528431.git.bristot@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The following RCU lockdep warning led to adding irq_enter()/irq_exit() into
smp_reschedule_interrupt():
RCU used illegally from idle CPU!
rcu_scheduler_active = 1, debug_locks = 0
RCU used illegally from extended quiescent state!
no locks held by swapper/1/0.
do_trace_write_msr
native_write_msr
native_apic_msr_eoi_write
smp_reschedule_interrupt
reschedule_interrupt
As Peterz pointed out:
| So now we're making a very frequent interrupt slower because of debug
| code.
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| The thing is, many many smp_reschedule_interrupt() invocations don't
| actually execute anything much at all and are only sent to tickle the
| return to user path (which does the actual preemption).
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| Having to do the whole irq_enter/irq_exit dance just for this unlikely
| debug case totally blows.
Use the wrmsr_notrace() variant in native_apic_msr_write_eoi, annotate the
kvm variant with notrace and add a native_apic_eoi callback to the apic
structure so KVM guests are covered as well.
This allows to revert the irq_enter/irq_exit dance in
smp_reschedule_interrupt().
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org
Cc: Mike Galbraith <efault@gmx.de>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/1478488420-5982-3-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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===============================
[ INFO: suspicious RCU usage. ]
4.8.0+ #24 Not tainted
-------------------------------
./arch/x86/include/asm/msr-trace.h:47 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
RCU used illegally from idle CPU!
rcu_scheduler_active = 1, debug_locks = 0
RCU used illegally from extended quiescent state!
no locks held by swapper/1/0.
[<ffffffff9d492b95>] do_trace_write_msr+0x135/0x140
[<ffffffff9d06f860>] native_write_msr+0x20/0x30
[<ffffffff9d065fad>] native_apic_msr_eoi_write+0x1d/0x30
[<ffffffff9d05bd1d>] smp_reschedule_interrupt+0x1d/0x30
[<ffffffff9d8daec6>] reschedule_interrupt+0x96/0xa0
Reschedule interrupt may be called in cpu idle state. This causes lockdep
check warning above.
Add irq_enter/exit() in smp_reschedule_interrupt(), irq_enter() tells the RCU
subsystems to end the extended quiescent state, so the following trace call in
ack_APIC_irq() works correctly.
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Link: http://lkml.kernel.org/r/1476409733-5133-1-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Daniel Walker reported problems which happens when
crash_kexec_post_notifiers kernel option is enabled
(https://lkml.org/lkml/2015/6/24/44).
In that case, smp_send_stop() is called before entering kdump routines
which assume other CPUs are still online. As the result, for x86, kdump
routines fail to save other CPUs' registers and disable virtualization
extensions.
To fix this problem, call a new kdump friendly function,
crash_smp_send_stop(), instead of the smp_send_stop() when
crash_kexec_post_notifiers is enabled. crash_smp_send_stop() is a weak
function, and it just call smp_send_stop(). Architecture codes should
override it so that kdump can work appropriately. This patch only
provides x86-specific version.
For Xen's PV kernel, just keep the current behavior.
NOTES:
- Right solution would be to place crash_smp_send_stop() before
__crash_kexec() invocation in all cases and remove smp_send_stop(), but
we can't do that until all architectures implement own
crash_smp_send_stop()
- crash_smp_send_stop()-like work is still needed by
machine_crash_shutdown() because crash_kexec() can be called without
entering panic()
Fixes: f06e5153f4ae (kernel/panic.c: add "crash_kexec_post_notifiers" option)
Link: http://lkml.kernel.org/r/20160810080948.11028.15344.stgit@sysi4-13.yrl.intra.hitachi.co.jp
Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com>
Reported-by: Daniel Walker <dwalker@fifo99.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Daniel Walker <dwalker@fifo99.com>
Cc: Xunlei Pang <xpang@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: David Daney <david.daney@cavium.com>
Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: "Steven J. Hill" <steven.hill@cavium.com>
Cc: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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All APIC implementation have send_IPI now. Remove the conditional in
the calling code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Travis <travis@sgi.com>
Cc: Daniel J Blueman <daniel@numascale.com>
Link: http://lkml.kernel.org/r/20151104220849.807817097@linutronix.de
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We still fall back on the "send mask" versions if an apic definition
doesn't have the single-target version, but at least this allows the
(trivial) case for the common clustered x2apic case.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Travis <travis@sgi.com>
Cc: Daniel J Blueman <daniel@numascale.com>
Link: http://lkml.kernel.org/r/20151104220848.737120838@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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kexec could boot a kernel that could be legacy with no knowledge
of LMCE. Hence we should make sure we clear LMCE optin before
kexec reboot.
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/1439396985-12812-9-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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smp.c and irq_work.c implement the same inline helper. Move it to
apic.h and use it everywhere.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
|
|
As requested by Linus add explicit __visible to the asmlinkage users.
This marks all functions visible to assembler.
Tree sweep for arch/x86/*
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1398984278-29319-3-git-send-email-andi@firstfloor.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
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|
These handlers are all referenced from assembler stubs, so need
to be visible.
The handlers without arguments become asmlinkage, the others __visible
to not force regparms(0) on x86-32.
I put it all into a single patch, please let me know if you want
it it split up.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Link: http://lkml.kernel.org/r/1375740170-7446-4-git-send-email-andi@firstfloor.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
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|
Reschedule vector tracepoints may be called in cpu idle state.
This causes lockdep check warning below.
The tracepoint requires rcu but for accuracy it also
requires irq_enter() (tracepoints record the irq context), thus,
the tracepoint interrupt handler should be calling irq_enter()
and not rcu_irq_enter() (irq_enter() calls rcu_irq_enter()).
So, add irq_enter/exit() to smp_trace_reschedule_interrupt()
with common pre/post processing functions, smp_entering_irq()
and exiting_irq() (exiting_irq() calls just irq_exit()
in arch/x86/include/asm/apic.h),
because these can be shared among reschedule, call_function,
and call_function_single vectors.
[ 50.720557] Testing event reschedule_exit:
[ 50.721349]
[ 50.721502] ===============================
[ 50.721835] [ INFO: suspicious RCU usage. ]
[ 50.722169] 3.10.0-rc6-00004-gcf910e8 #190 Not tainted
[ 50.722582] -------------------------------
[ 50.722915] /c/kernel-tests/src/linux/arch/x86/include/asm/trace/irq_vectors.h:50 suspicious rcu_dereference_check() usage!
[ 50.723770]
[ 50.723770] other info that might help us debug this:
[ 50.723770]
[ 50.724385]
[ 50.724385] RCU used illegally from idle CPU!
[ 50.724385] rcu_scheduler_active = 1, debug_locks = 0
[ 50.725232] RCU used illegally from extended quiescent state!
[ 50.725690] no locks held by swapper/0/0.
[ 50.726010]
[ 50.726010] stack backtrace:
[...]
Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/51CDCFA3.9080101@hds.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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|
[Purpose of this patch]
As Vaibhav explained in the thread below, tracepoints for irq vectors
are useful.
http://www.spinics.net/lists/mm-commits/msg85707.html
<snip>
The current interrupt traces from irq_handler_entry and irq_handler_exit
provide when an interrupt is handled. They provide good data about when
the system has switched to kernel space and how it affects the currently
running processes.
There are some IRQ vectors which trigger the system into kernel space,
which are not handled in generic IRQ handlers. Tracing such events gives
us the information about IRQ interaction with other system events.
The trace also tells where the system is spending its time. We want to
know which cores are handling interrupts and how they are affecting other
processes in the system. Also, the trace provides information about when
the cores are idle and which interrupts are changing that state.
<snip>
On the other hand, my usecase is tracing just local timer event and
getting a value of instruction pointer.
I suggested to add an argument local timer event to get instruction pointer before.
But there is another way to get it with external module like systemtap.
So, I don't need to add any argument to irq vector tracepoints now.
[Patch Description]
Vaibhav's patch shared a trace point ,irq_vector_entry/irq_vector_exit, in all events.
But there is an above use case to trace specific irq_vector rather than tracing all events.
In this case, we are concerned about overhead due to unwanted events.
So, add following tracepoints instead of introducing irq_vector_entry/exit.
so that we can enable them independently.
- local_timer_vector
- reschedule_vector
- call_function_vector
- call_function_single_vector
- irq_work_entry_vector
- error_apic_vector
- thermal_apic_vector
- threshold_apic_vector
- spurious_apic_vector
- x86_platform_ipi_vector
Also, introduce a logic switching IDT at enabling/disabling time so that a time penalty
makes a zero when tracepoints are disabled. Detailed explanations are as follows.
- Create trace irq handlers with entering_irq()/exiting_irq().
- Create a new IDT, trace_idt_table, at boot time by adding a logic to
_set_gate(). It is just a copy of original idt table.
- Register the new handlers for tracpoints to the new IDT by introducing
macros to alloc_intr_gate() called at registering time of irq_vector handlers.
- Add checking, whether irq vector tracing is on/off, into load_current_idt().
This has to be done below debug checking for these reasons.
- Switching to debug IDT may be kicked while tracing is enabled.
- On the other hands, switching to trace IDT is kicked only when debugging
is disabled.
In addition, the new IDT is created only when CONFIG_TRACING is enabled to avoid being
used for other purposes.
Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
Link: http://lkml.kernel.org/r/51C323ED.5050708@hds.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
|
|
When implementing tracepoints in interrupt handers, if the tracepoints are
simply added in the performance sensitive path of interrupt handers,
it may cause potential performance problem due to the time penalty.
To solve the problem, an idea is to prepare non-trace/trace irq handers and
switch their IDTs at the enabling/disabling time.
So, let's introduce entering_irq()/exiting_irq() for pre/post-
processing of each irq handler.
A way to use them is as follows.
Non-trace irq handler:
smp_irq_handler()
{
entering_irq(); /* pre-processing of this handler */
__smp_irq_handler(); /*
* common logic between non-trace and trace handlers
* in a vector.
*/
exiting_irq(); /* post-processing of this handler */
}
Trace irq_handler:
smp_trace_irq_handler()
{
entering_irq(); /* pre-processing of this handler */
trace_irq_entry(); /* tracepoint for irq entry */
__smp_irq_handler(); /*
* common logic between non-trace and trace handlers
* in a vector.
*/
trace_irq_exit(); /* tracepoint for irq exit */
exiting_irq(); /* post-processing of this handler */
}
If tracepoints can place outside entering_irq()/exiting_irq() as follows,
it looks cleaner.
smp_trace_irq_handler()
{
trace_irq_entry();
smp_irq_handler();
trace_irq_exit();
}
But it doesn't work.
The problem is with irq_enter/exit() being called. They must be called before
trace_irq_enter/exit(), because of the rcu_irq_enter() must be called before
any tracepoints are used, as tracepoints use rcu to synchronize.
As a possible alternative, we may be able to call irq_enter() first as follows
if irq_enter() can nest.
smp_trace_irq_hander()
{
irq_entry();
trace_irq_entry();
smp_irq_handler();
trace_irq_exit();
irq_exit();
}
But it doesn't work, either.
If irq_enter() is nested, it may have a time penalty because it has to check if it
was already called or not. The time penalty is not desired in performance sensitive
paths even if it is tiny.
Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
Link: http://lkml.kernel.org/r/51C3238D.9040706@hds.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
|
|
Update the nonmi_ipi parameter to reflect the simple change
instead of the previous complicated one. There should be less
of a need to use it but there may still be corner cases on older
hardware that stumble into NMI issues.
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1336761675-24296-4-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
For v3.3, I added code to use the NMI to stop other cpus in the
panic case. The idea was to make sure all cpus on the system
were definitely halted to help serialize the panic path to
execute the rest of the code on a single cpu.
The main problem it was trying to solve was how to stop a cpu
that was spinning with its irqs disabled. A IPI irq would be
stuck and couldn't get in there, but an NMI could.
Things were great until we had another conversation about some
pstore changes. Because some of the backend pstore still uses
spinlocks to protect the device access, things could get ugly if
a panic happened and we were stuck spinning on a lock.
Now with the NMI shutting down cpus, we could assume no other
cpus were running and just bust the spin lock and proceed.
The counter argument was, well if you do that the backend could
be in a screwed up state and you might not be able to save
anything as a result. If we could have just given the cpu a
little more time to finish things, we could have grabbed the
spin lock cleanly and everything would have been fine.
Well, how do give a cpu a 'little more time' in the panic case?
For the most part you can't without spinning on the lock and
even in that case, how long do you spin for?
So instead of making it ugly in the pstore code, just mimic the
idea that stop_machine had, which is block on an IRQ IPI until
the remote cpu has re-enabled interrupts and left the critical
region. Which is what happens now using REBOOT_IRQ.
Then leave the NMI case for those cpus that are truly stuck
after a short time. This leaves the current behaviour alone and
just handle a corner case. Most systems should never have to
enter the NMI code and if they do, print out a message in case
the NMI itself causes another issue.
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1336761675-24296-3-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
|
|
This reverts commit 3603a2512f9e69dc87914ba922eb4a0812b21cd6.
Originally I wanted a better hammer to shutdown cpus during
panic. However, this really steps on the toes of various
spinlocks in the panic path. Sometimes it is easier to wait for
the IRQ to become re-enabled to indictate the cpu left the
critical region and then shutdown the cpu.
The next patch moves the NMI addition after the IRQ part. To
make it easier to see the logic of everything, revert this patch
and apply the next simpler patch.
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1336761675-24296-2-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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|
It was brought to my attention that my x86 change to use NMI in
the reboot path broke Intel Nehalem and Westmere boxes when
using kexec.
I realized I had mistyped the if statement in commit
3603a2512f9e69dc87914ba922eb4a0812b21cd6 and stuck the ')' in
the wrong spot. Putting it in the right spot fixes kexec again.
Doh.
Reported-by: Yinghai Lu <yinghai@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Link: http://lkml.kernel.org/r/1325866671-9797-1-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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|
Some machines may exhibit problems using the NMI to stop other
cpus. This knob just allows one to revert back to the original
behaviour to help diagnose the problem.
V2:
make function static
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Richter <robert.richter@amd.com>
Cc: seiji.aguchi@hds.com
Cc: vgoyal@redhat.com
Cc: mjg@redhat.com
Cc: tony.luck@intel.com
Cc: gong.chen@intel.com
Cc: satoru.moriya@hds.com
Cc: avi@redhat.com
Cc: Andi Kleen <andi@firstfloor.org>
Link: http://lkml.kernel.org/r/1318533267-18880-4-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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|
A recent discussion started talking about the locking on the
pstore fs and how it relates to the kmsg infrastructure. We
noticed it was possible for userspace to r/w to the pstore fs
(grabbing the locks in the process) and block the panic path
from r/w to the same fs.
The reason was the cpu with the lock could be doing work while
the crashing cpu is panic'ing. Busting those spinlocks might
cause those cpus to step on each other's data. Fine, fair
enough.
It was suggested it would be nice to serialize the panic path
(ie stop the other cpus) and have only one cpu running. This
would allow us to bust the spinlocks and not worry about another
cpu stepping on the data.
Of course, smp_send_stop() does this in the panic case.
kmsg_dump() would have to be moved to be called after it. Easy
enough.
The only problem is on x86 the smp_send_stop() function calls
the REBOOT_VECTOR. Any cpu with irqs disabled (which pstore and
its backend ERST would do), block this IPI and thus do not stop.
This makes it difficult to reliably log data to the pstore fs.
The patch below switches from the REBOOT_VECTOR to NMI (and
mimics what kdump does). Switching to NMI allows us to deliver
the IPI when irqs are disabled, increasing the reliability of
this function.
However, Andi carefully noted that on some machines this
approach does not work because of broken BIOSes or whatever.
To help accomodate this, the next couple of patches will run a
selftest and provide a knob to disable.
V2:
uses atomic ops to serialize the cpu that shuts everyone down
V3:
comment cleanup
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert Richter <robert.richter@amd.com>
Cc: seiji.aguchi@hds.com
Cc: vgoyal@redhat.com
Cc: mjg@redhat.com
Cc: tony.luck@intel.com
Cc: gong.chen@intel.com
Cc: satoru.moriya@hds.com
Cc: avi@redhat.com
Cc: Andi Kleen <andi@firstfloor.org>
Link: http://lkml.kernel.org/r/1318533267-18880-2-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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These files were implicitly getting EXPORT_SYMBOL via device.h
which was including module.h, but that will be fixed up shortly.
By fixing these now, we can avoid seeing things like:
arch/x86/kernel/rtc.c:29: warning: type defaults to ‘int’ in declaration of ‘EXPORT_SYMBOL’
arch/x86/kernel/pci-dma.c:20: warning: type defaults to ‘int’ in declaration of ‘EXPORT_SYMBOL’
arch/x86/kernel/e820.c:69: warning: type defaults to ‘int’ in declaration of ‘EXPORT_SYMBOL_GPL’
[ with input from Randy Dunlap <rdunlap@xenotime.net> and also
from Stephen Rothwell <sfr@canb.auug.org.au> ]
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
|
|
For future rework of try_to_wake_up() we'd like to push part of that
function onto the CPU the task is actually going to run on.
In order to do so we need a generic callback from the existing scheduler IPI.
This patch introduces such a generic callback: scheduler_ipi() and
implements it as a NOP.
BenH notes: PowerPC might use this IPI on offline CPUs under rare conditions!
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Chris Metcalf <cmetcalf@tilera.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Reviewed-by: Frank Rowand <frank.rowand@am.sony.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20110405152728.744338123@chello.nl
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x86 smp_ops now has a new op, stop_other_cpus which takes a parameter
"wait" this allows the caller to specify if it wants to stop until all
the cpus have processed the stop IPI. This is required specifically
for the kexec case where we should wait for all the cpus to be stopped
before starting the new kernel. We now wait for the cpus to stop in
all cases except for panic/kdump where we expect things to be broken
and we are doing our best to make things work anyway.
This patch fixes a legitimate regression, which was introduced during
2.6.30, by commit id 4ef702c10b5df18ab04921fc252c26421d4d6c75.
Signed-off-by: Alok N Kataria <akataria@vmware.com>
LKML-Reference: <1286833028.1372.20.camel@ank32.eng.vmware.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: <stable@kernel.org> v2.6.30-36
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
|
|
implicit slab.h inclusion from percpu.h
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.
percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.
http://userweb.kernel.org/~tj/misc/slabh-sweep.py
The script does the followings.
* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.
* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.
* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.
The conversion was done in the following steps.
1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.
2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.
3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.
4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.
5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.
6. percpu.h was updated not to include slab.h.
7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).
* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig
8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.
Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
|
|
This reverts commit 9bcbdd9c58617f1301dd4f17c738bb9bc73aca70.
The real bug producing LatencyTop latencies has been fixed in:
f5dc375: sched: Update the clock of runqueue select_task_rq() selected
And the commit being reverted here triggers local timer processing
from every device IRQ. If device IRQs come in at a high frequency,
this could cause a performance regression.
The commit being reverted here purely 'fixed' the reported latency
as a side effect, because CPUs were being moved out of idle more
often.
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Frans Pop <elendil@planet.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <20091008064041.67219b13@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
|
|
Now that range timers and deferred timers are common, I found a
problem with these using the "perf timechart" tool. Frans Pop also
reported high scheduler latencies via LatencyTop, when using
iwlagn.
It turns out that on x86, these two 'opportunistic' timers only get
checked when another "real" timer happens. These opportunistic
timers have the objective to save power by hitchhiking on other
wakeups, as to avoid CPU wakeups by themselves as much as possible.
The change in this patch runs this check not only at timer
interrupts, but at all (device) interrupts. The effect is that:
1) the deferred timers/range timers get delayed less
2) the range timers cause less wakeups by themselves because
the percentage of hitchhiking on existing wakeup events goes up.
I've verified the working of the patch using "perf timechart", the
original exposed bug is gone with this patch. Frans also reported
success - the latencies are now down in the expected ~10 msec
range.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Tested-by: Frans Pop <elendil@planet.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20091008064041.67219b13@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
|
|
Conflicts:
arch/x86/kernel/cpu/mcheck/mce_64.c
arch/x86/kernel/irq.c
Merge reason: Resolve the conflicts above.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
|
|
* 'kvm-updates/2.6.31' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (138 commits)
KVM: Prevent overflow in largepages calculation
KVM: Disable large pages on misaligned memory slots
KVM: Add VT-x machine check support
KVM: VMX: Rename rmode.active to rmode.vm86_active
KVM: Move "exit due to NMI" handling into vmx_complete_interrupts()
KVM: Disable CR8 intercept if tpr patching is active
KVM: Do not migrate pending software interrupts.
KVM: inject NMI after IRET from a previous NMI, not before.
KVM: Always request IRQ/NMI window if an interrupt is pending
KVM: Do not re-execute INTn instruction.
KVM: skip_emulated_instruction() decode instruction if size is not known
KVM: Remove irq_pending bitmap
KVM: Do not allow interrupt injection from userspace if there is a pending event.
KVM: Unprotect a page if #PF happens during NMI injection.
KVM: s390: Verify memory in kvm run
KVM: s390: Sanity check on validity intercept
KVM: s390: Unlink vcpu on destroy - v2
KVM: s390: optimize float int lock: spin_lock_bh --> spin_lock
KVM: s390: use hrtimer for clock wakeup from idle - v2
KVM: s390: Fix memory slot versus run - v3
...
|
|
KVM uses a function call IPI to cause the exit of a guest running on a
physical cpu. For virtual interrupt notification there is no need to
wait on IPI receival, or to execute any function.
This is exactly what the reschedule IPI does, without the overhead
of function IPI. So use it instead of smp_call_function_single in
kvm_vcpu_kick.
Also change the "guest_mode" variable to a bit in vcpu->requests, and
use that to collapse multiple IPI's that would be issued between the
first one and zeroing of guest mode.
This allows kvm_vcpu_kick to called with interrupts disabled.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
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For some time each panic() called with interrupts disabled
triggered the !irqs_disabled() WARN_ON in smp_call_function(),
producing ugly backtraces and confusing users.
This is a common situation with machine checks for example which
tend to call panic with interrupts disabled, but will also hit
in other situations e.g. panic during early boot. In fact it
means that panic cannot be called in many circumstances, which
would be bad.
This all started with the new fancy queued smp_call_function,
which is then used by the shutdown path to shut down the other
CPUs.
On closer examination it turned out that the fancy RCU
smp_call_function() does lots of things not suitable in a panic
situation anyways, like allocating memory and relying on complex
system state.
I originally tried to patch this over by checking for panic
there, but it was quite complicated and the original patch
was also not very popular. This also didn't fix some of the
underlying complexity problems.
The new code in post 2.6.29 tries to patch around this by
checking for oops_in_progress, but that is not enough to make
this fully safe and I don't think that's a real solution
because panic has to be reliable.
So instead use an own vector to reboot. This makes the reboot
code extremly straight forward, which is definitely a big plus
in a panic situation where it is important to avoid relying on
too much kernel state. The new simple code is also safe to be
called from interupts off region because it is very very simple.
There can be situations where it is important that panic
is reliable. For example on a fatal machine check the panic
is needed to get the system up again and running as quickly
as possible. So it's important that panic is reliable and
all function it calls simple.
This is why I came up with this simple vector scheme.
It's very hard to beat in simplicity. Vectors are not
particularly precious anymore since all big systems are
using per CPU vectors.
Another possibility would have been to use an NMI similar
to kdump, but there is still the problem that NMIs don't
work reliably on some systems due to BIOS issues. NMIs
would have been able to stop CPUs running with interrupts
off too. In the sake of universal reliability I opted for
using a non NMI vector for now.
I put the reboot vector into the highest priority bucket of
the APIC vectors and moved the 64bit UV_BAU message down
instead into the next lower priority.
[ Impact: bug fix, fixes an old regression ]
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
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Impact: cleanup
It's a bit hard to parse by eyes without
them being aligned.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
LKML-Reference: <20090412165058.924175574@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Impact: cleanup
Remove genapic.h and remove all references to it.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Move mach_ipi.h definitions into genapic.h.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Spread mach_apic.h definitions into genapic.h. (with some knock-on effects
on smp.h and apic.h.)
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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