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Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
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Fix a race condition during AP device registration and unregistration.
Signed-off-by: Ralph Wuerthner <rwuerthn@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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While the machine owns us an interrupt in these cases (and we should get
one), reality isn't always like that...
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Fix new restore_sigregs function. It copies the user space copy of the
old psw without correcting the psw.mask and the psw.addr high order bit.
While we are at it, simplify save_sigregs a bit.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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* 'for-2.6.19' of git://brick.kernel.dk/data/git/linux-2.6-block:
[PATCH] Document bi_sector and sector_t
[PATCH] helper function for retrieving scsi_cmd given host based block layer tag
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* 'upstream' of git://ftp.linux-mips.org/pub/scm/upstream-linus:
[MIPS] Remove remaining reference to ite_gpio.h from Kbuild
[MIPS] PNX8550 fixups
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Signed-Off-By: Roger Gammans <rgammans@computer-surgery.co.uk>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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This was necessitated by the need for a function to get back
to a scsi_cmnd, when an hba the posts its (corresponding) completion
interrupt with a block layer tag as its reference.
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: David Somayajulu <david.somayajulu@qlogic.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
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* master.kernel.org:/pub/scm/linux/kernel/git/mchehab/v4l-dvb:
V4L/DVB (4712): Fix warning when compiling on x86_i64
V4L/DVB (4711): Radio: No need to return void
V4L/DVB (4708): Add tveeprom support for Philips FM1236/FM1216ME MK5
V4L/DVB (4707): 4linux: complete conversion to hotplug safe PCI API
V4L/DVB (4706): Do not enable VIDEO_V4L2 unconditionally
V4L/DVB (4704): SAA713x: fixed compile warning in SECAM fixup
V4L/DVB (4703): Add support for the ASUS EUROPA2 OEM board
V4L/DVB (4702): Fix: set antenna input for DVB-T for Asus P7131 Dual hybrid
V4L/DVB (4701): Saa713x audio fixes
V4L/DVB (4676a): Remove Kconfig item for DiB7000M support
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The atmel_console_get_options() function initializes the baud,
parity and bits settings from the actual hardware setup, in
case it has been initialized by a e.g. boot loader.
The baud rate, however, is not necessarily exactly equal to one of
the standard baud rates (115200, etc.) This means that the baud rate
calculated by this function may be slightly higher or slightly lower
than one of the standard baud rates.
If the baud rate is slightly lower than the target, this causes
problems when uart_set_option() tries to match the detected baud rate
against the standard baud rate, as it will always select a baud rate
that is lower or equal to the target rate. For example if the
detected baud rate is slightly lower than 115200, usart_set_options()
will select 57600.
This patch fixes the problem by subtracting 1 from the value in BRGR
when calculating the baud rate. The detected baud rate will thus
always be higher than the nearest standard baud rate, and
uart_set_options() will end up doing the right thing.
Tested on ATSTK1000 and AT91RM9200-EK boards. Both are broken without
this patch.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Allow the board to remap actual USART peripheral devices to serial
devices by calling at32_map_usart(hw_id, serial_line). This ensures
that even though ATSTK1002 uses USART1 as the first serial port, it
will still have a ttyS0 device.
This also adds a board-specific early setup hook and moves the
at32_setup_serial_console() call there from the platform code.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Make CONFIG_SERIAL_ATMEL selectable on AVR32 and #ifdef out some ARM-
specific code in the driver.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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In order to initialize the serial console early, the atmel_serial
driver had to do a hack where it compared the physical address of the
port with an address known to be permanently mapped, and used it as a
virtual address. This got around the limitation that ioremap() isn't
always available when the console is being initalized.
This patch removes that hack and replaces it with a new "regs" field
in struct atmel_uart_data that the board-specific code can initialize
to a fixed virtual mapping for platform devices where this is possible.
It also initializes the DBGU's regs field with the address the driver
used to check against.
On AVR32, the "regs" field is initialized from the physical base
address when this it can be accessed through a permanently 1:1 mapped
segment, i.e. the P4 segment.
If regs is NULL, the console initialization is delayed until the "real"
driver is up and running and ioremap() can be used.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Rename at91_register_uart_fns and associated structs and variables
to make it consistent with the atmel_ prefix used by the rest of
the driver.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The at91_serial driver can be used with both AT32 and AT91 devices
from Atmel and has therefore been renamed atmel_serial. The only
thing left is to rename PORT_AT91 PORT_ATMEL.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Prefix all internal functions and variables with atmel_ instead of
at91_.
The at91_register_uart_fns() stuff is left as is since I can't find
any actual users of it.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Rename the following public definitions:
* AT91_NR_UART -> ATMEL_MAX_UART
* struct at91_uart_data -> struct atmel_uart_data
* at91_default_console_device -> atmel_default_console_device
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Rename the "at91_usart" platform driver "atmel_usart" and update
platform devices accordingly.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Rename the following Kconfig symbols:
* CONFIG_SERIAL_AT91 -> CONFIG_SERIAL_ATMEL
* CONFIG_SERIAL_AT91_CONSOLE -> CONFIG_SERIAL_ATMEL_CONSOLE
* CONFIG_SERIAL_AT91_TTYAT -> CONFIG_SERIAL_ATMEL_TTYAT
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Rename at91_serial.c atmel_serial.c
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Move include/asm/arch/at91rm9200_usart.h into drivers/serial and rename
it atmel_usart.h. Also delete AVR32's version of this file.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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This patch fixes the compilation errors on PNX8550 and hard-to-track
bug in interrupt handling.
It also corresponds to the latest changes in PNX8550 serial driver.
Signed-off-by: Vitaly Wool <vitalywool@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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* master.kernel.org:/pub/scm/linux/kernel/git/davej/configh:
Remove all inclusions of <linux/config.h>
Manually resolved trivial path conflicts due to removed files in
the sound/oss/ subdirectory.
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* git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-2.6: (292 commits)
[GFS2] Fix endian bug for de_type
[GFS2] Initialize SELinux extended attributes at inode creation time.
[GFS2] Move logging code into log.c (mostly)
[GFS2] Mark nlink cleared so VFS sees it happen
[GFS2] Two redundant casts removed
[GFS2] Remove uneeded endian conversion
[GFS2] Remove duplicate sb reading code
[GFS2] Mark metadata reads for blktrace
[GFS2] Remove iflags.h, use FS_
[GFS2] Fix code style/indent in ops_file.c
[GFS2] streamline-generic_file_-interfaces-and-filemap gfs fix
[GFS2] Remove readv/writev methods and use aio_read/aio_write instead (gfs bits)
[GFS2] inode-diet: Eliminate i_blksize from the inode structure
[GFS2] inode_diet: Replace inode.u.generic_ip with inode.i_private (gfs)
[GFS2] Fix typo in last patch
[GFS2] Fix direct i/o logic in filemap.c
[GFS2] Fix bug in Makefiles for lock modules
[GFS2] Remove (extra) fs_subsys declaration
[GFS2/DLM] Fix trailing whitespace
[GFS2] Tidy up meta_io code
...
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* master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6:
[XFRM]: BEET mode
[TCP]: Kill warning in tcp_clean_rtx_queue().
[NET_SCHED]: Remove old estimator implementation
[ATM]: [zatm] always *pcr in alloc_shaper()
[ATM]: [ambassador] Change the return type to reflect reality
[ATM]: kmalloc to kzalloc patches for drivers/atm
[TIPC]: fix printk warning
[XFRM]: Clearing xfrm_policy_count[] to zero during flush is incorrect.
[XFRM] STATE: Use destination address for src hash.
[NEIGH]: always use hash_mask under tbl lock
[UDP]: Fix MSG_PROBE crash
[UDP6]: Fix flowi clobbering
[NET_SCHED]: Revert "HTB: fix incorrect use of RB_EMPTY_NODE"
[NETFILTER]: ebt_mark: add or/and/xor action support to mark target
[NETFILTER]: ipt_REJECT: remove largely duplicate route_reverse function
[NETFILTER]: Honour source routing for LVS-NAT
[NETFILTER]: add type parameter to ip_route_me_harder
[NETFILTER]: Kconfig: fix xt_physdev dependencies
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* master.kernel.org:/pub/scm/linux/kernel/git/willy/parisc-2.6: (41 commits)
[PARISC] Kill wall_jiffies use
[PARISC] Honour "panic_on_oops" sysctl
[PARISC] Fix fs/binfmt_som.c
[PARISC] Export clear_user_page to modules
[PARISC] Make DMA routines more stubby
[PARISC] Define pci_get_legacy_ide_irq
[PARISC] Fix CONFIG_DEBUG_SPINLOCK
[PARISC] Fix HPUX compat compile with current GCC
[PARISC] Fix iounmap compile warning
[PARISC] Add support for Quicksilver AGPGART
[PARISC] Move LBA and SBA register defines to the common ropes.h
[PARISC] Create shared <asm/ropes.h> header
[PARISC] Stash the lba_device in its struct device drvdata
[PARISC] Generalize IS_ASTRO et al to take a parisc_device like
[PARISC] Pretty print the name of the lba type on kernel boot
[PARISC] Remove some obsolete comments and I checked that Reo is similar to Ike
[PARISC] Add hardware found in the rp8400
[PARISC] Allow nested interrupts
[PARISC] Further updates to timer_interrupt()
[PARISC] remove halftick and copy clocktick to local var (gcc can optimize usage)
...
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* git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc: (25 commits)
[POWERPC] Add support for the mpc832x mds board
[POWERPC] Add initial support for the e300c2 core
[POWERPC] Add MPC8360EMDS default dts file
[POWERPC] Add MPC8360EMDS board support
[POWERPC] Add QUICC Engine (QE) infrastructure
[POWERPC] Add QE device tree node definition
[POWERPC] Don't try to just continue if xmon has no input device
[POWERPC] Fix a printk in pseries_mpic_init_IRQ
[POWERPC] Get default baud rate in udbg_scc
[POWERPC] Fix zImage.coff on oldworld PowerMac
[POWERPC] Fix xmon=off and cleanup xmon initialisation
[POWERPC] Cleanup include/asm-powerpc/xmon.h
[POWERPC] Update swim3 printk after blkdev.h change
[POWERPC] Cell interrupt rework
POWERPC: mpc82xx merge: board-specific/platform stuff(resend)
POWERPC: 8272ads merge to powerpc: common stuff
POWERPC: Added devicetree for mpc8272ads board
[POWERPC] iSeries has no legacy I/O
[POWERPC] implement BEGIN/END_FW_FTR_SECTION
[POWERPC] iSeries does not need pcibios_fixup_resources
...
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git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit-current
* 'audit.b32' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/audit-current:
[PATCH] message types updated
[PATCH] name_count array overrun
[PATCH] PPID filtering fix
[PATCH] arch filter lists with < or > should not be accepted
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This fixes support for rev c8 of the ALi/ULi PATA, and keeps pcmcia in
sync so ide_cs and pata_pcmcia are interchangable, both are only changes
to constants.
Right now rev 0xC8 and higher don't work with libata but 0xc8 is in the
field now.
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Fix obvious build breakage revealed by 'make allyesconfig'
in current -git.
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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master.kernel.org:/pub/scm/linux/kernel/git/jgarzik/libata-dev
* 'upstream-linus' of master.kernel.org:/pub/scm/linux/kernel/git/jgarzik/libata-dev:
[libata] pata_artop: kill gcc warning
[PATCH] libata: turn off NCQ if queue depth is adjusted to 1
[PATCH] libata: cosmetic changes to constants
[libata] DocBook minor updates, fixes
[libata] PCI ID table cleanup in various drivers
[libata] Print out Status register, if a BSY-sleep takes too long
[libata] init probe_ent->private_data in a common location
[libata] minor PCI IDE probe fixes and cleanups
[libata] Use new PCI_VDEVICE() macro to dramatically shorten ID lists
[PATCH] Fix reference of uninitialised memory in ata_device_add()
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If you lose the x bit (eg: by using patch(1)), powerpc won't build. Be
defensive about it...
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Move all EXPORT_SYMBOL's from sound/oss/*_syms.c to the files with the
actual functions.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch contains the scheduled removal of OSS drivers that:
- have ALSA drivers for the same hardware without known regressions and
- whose Kconfig options have been removed in 2.6.17.
[michal.k.k.piotrowski@gmail.com: build fix]
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Michal Piotrowski <michal.k.k.piotrowski@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Add MAINTAINERS entry for Read-Copy Update (RCU), listing Dipankar Sarma as
maintainer, and giving the URL for Paul McKenney's RCU site. Add
MAINTAINERS entry for rcutorture, listing myself as maintainer. Add
CREDITS entries for developers of RCU, RCU variants, and rcutorture. Use
Paul McKenney's preferred email address in include/linux/rcupdate.h .
Signed-off-by: Josh Triplett <josh@freedesktop.org>
Cc: Paul McKenney <paulmck@us.ibm.com>
Cc: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Kill a hard-to-calculate 'rsinterval' boot parameter and per-cpu
rcu_data.last_rs_qlen. Instead, it adds adds a flag rcu_ctrlblk.signaled,
which records the fact that one of CPUs has sent a resched IPI since the
last rcu_start_batch().
Roughly speaking, we need two rcu_start_batch()s in order to move callbacks
from ->nxtlist to ->donelist. This means that when ->qlen exceeds qhimark
and continues to grow, we should send a resched IPI, and then do it again
after we gone through a quiescent state.
On the other hand, if it was already sent, we don't need to do it again
when another CPU detects overflow of the queue.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Implement torture testing for the "sched" variant of RCU, which uses
preempt_disable, preempt_enable, and synchronize_sched.
Signed-off-by: Josh Triplett <josh@freedesktop.org>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Use the newly-generic synchronous deferred free function to implement torture
testing for rcu_bh using synchronize_rcu_bh rather than the asynchronous
call_rcu_bh.
Signed-off-by: Josh Triplett <josh@freedesktop.org>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Use the newly-generic synchronous deferred free function to implement torture
testing for RCU using synchronize_rcu rather than the asynchronous call_rcu.
Signed-off-by: Josh Triplett <josh@freedesktop.org>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Make srcu_torture_deferred_free use cur_ops->sync() so it will work for any
implementation. Move and rename it in preparation for use in the ops of other
implementations.
Signed-off-by: Josh Triplett <josh@freedesktop.org>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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rcutorture currently has one writer and an arbitrary number of readers. To
better exercise some of the code paths in RCU implementations, add fake
writer threads which call the synchronize function for the RCU variant in a
loop, with a delay between calls to arrange for different numbers of
writers running in parallel.
[bunk@stusta.de: cleanup]
Acked-by: Paul McKenney <paulmck@us.ibm.com>
Cc: Dipkanar Sarma <dipankar@in.ibm.com>
Signed-off-by: Josh Triplett <josh@freedesktop.org>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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rcu_random uses a counter rrs_count to occasionally mix data from
get_random_bytes into the state of its pseudorandom generator. However,
the rrs_counter gets declared as an unsigned long, and rcu_random checks
for --rrs_count < 0, so this code will never mix any real random data into
the state, and will thus always return the same sequence of random numbers.
Also, change the return value of rcu_random from long to unsigned long, to
avoid potential issues caused by the use of the % operator, which can
return negative values for negative left operands.
Signed-off-by: Josh Triplett <josh@freedesktop.org>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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startup fails
rcu_torture_init kmallocs the array of reader threads, then creates each
one with kthread_run, cleaning up with rcu_torture_cleanup if this fails.
rcu_torture_cleanup calls kthread_stop on any non-NULL pointer in the
array; however, any readers after the one that failed to start up will have
invalid pointers, not null pointers. Avoid this by using kzalloc instead.
Signed-off-by: Josh Triplett <josh@freedesktop.org>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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parameter
The comment for rcutorture's torture_type parameter only lists the RCU
variants rcu and srcu, but not rcu_bh; add rcu_bh to the list.
Signed-off-by: Josh Triplett <josh@freedesktop.org>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Signed-off-by: Josh Triplett <josh@freedesktop.org>
Acked-by: "Paul E. McKenney" <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch (as762) changes the cpufreq_transition_notifier_list from a
blocking_notifier_head to an srcu_notifier_head. This will prevent errors
caused attempting to call down_read() to access the notifier chain at a
time when interrupts must remain disabled, during system suspend.
It's not clear to me whether this is really necessary; perhaps the chain
could be made into an atomic_notifier. However a couple of the callout
routines do use blocking operations, so this approach seems safer.
The head of the notifier chain needs to be initialized before use; this is
done by an __init routine at core_initcall time. If this turns out not to
be a good choice, it can easily be changed.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Jesse Brandeburg <jesse.brandeburg@gmail.com>
Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Currently the init_srcu_struct() routine has no way to report out-of-memory
errors. This patch (as761) makes it return -ENOMEM when the per-cpu data
allocation fails.
The patch also makes srcu_init_notifier_head() report a BUG if a notifier
head can't be initialized. Perhaps it should return -ENOMEM instead, but
in the most likely cases where this might occur I don't think any recovery
is possible. Notifier chains generally are not created dynamically.
[akpm@osdl.org: avoid statement-with-side-effect in macro]
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch (as751) adds a new type of notifier chain, based on the SRCU
(Sleepable Read-Copy Update) primitives recently added to the kernel. An
SRCU notifier chain is much like a blocking notifier chain, in that it must
be called in process context and its callout routines are allowed to sleep.
The difference is that the chain's links are protected by the SRCU
mechanism rather than by an rw-semaphore, so calling the chain has
extremely low overhead: no memory barriers and no cache-line bouncing. On
the other hand, unregistering from the chain is expensive and the chain
head requires special runtime initialization (plus cleanup if it is to be
deallocated).
SRCU notifiers are appropriate for notifiers that will be called very
frequently and for which unregistration occurs very seldom. The proposed
"task notifier" scheme qualifies, as may some of the network notifiers.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Paul E. McKenney <paulmck@us.ibm.com>
Acked-by: Chandra Seetharaman <sekharan@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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