diff options
| author | Athira Rajeev <atrajeev@linux.vnet.ibm.com> | 2020-12-01 04:28:00 -0500 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2020-12-04 01:01:21 +1100 |
| commit | f66de7ac4849eb42a7b18e26b8ee49e08130fd27 (patch) | |
| tree | 2d855ca48ac68b20598de236f85587b793a313e3 /arch/powerpc/perf | |
| parent | c9344769e2b46ba28b947bec7a8a8f0a091ecd57 (diff) | |
powerpc/perf: Invoke per-CPU variable access with disabled interrupts
The power_pmu_event_init() callback access per-cpu variable
(cpu_hw_events) to check for event constraints and Branch Stack
(BHRB). Current usage is to disable preemption when accessing the
per-cpu variable, but this does not prevent timer callback from
interrupting event_init. Fix this by using 'local_irq_save/restore'
to make sure the code path is invoked with disabled interrupts.
This change is tested in mambo simulator to ensure that, if a timer
interrupt comes in during the per-cpu access in event_init, it will be
soft masked and replayed later. For testing purpose, introduced a
udelay() in power_pmu_event_init() to make sure a timer interrupt arrives
while in per-cpu variable access code between local_irq_save/resore.
As expected the timer interrupt was replayed later during local_irq_restore
called from power_pmu_event_init. This was confirmed by adding
breakpoint in mambo and checking the backtrace when timer_interrupt
was hit.
Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1606814880-1720-1-git-send-email-atrajeev@linux.vnet.ibm.com
Diffstat (limited to 'arch/powerpc/perf')
| -rw-r--r-- | arch/powerpc/perf/core-book3s.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c index 8e20ef6252e1..6e224650b3c9 100644 --- a/arch/powerpc/perf/core-book3s.c +++ b/arch/powerpc/perf/core-book3s.c @@ -1912,7 +1912,7 @@ static bool is_event_blacklisted(u64 ev) static int power_pmu_event_init(struct perf_event *event) { u64 ev; - unsigned long flags; + unsigned long flags, irq_flags; struct perf_event *ctrs[MAX_HWEVENTS]; u64 events[MAX_HWEVENTS]; unsigned int cflags[MAX_HWEVENTS]; @@ -2020,7 +2020,9 @@ static int power_pmu_event_init(struct perf_event *event) if (check_excludes(ctrs, cflags, n, 1)) return -EINVAL; - cpuhw = &get_cpu_var(cpu_hw_events); + local_irq_save(irq_flags); + cpuhw = this_cpu_ptr(&cpu_hw_events); + err = power_check_constraints(cpuhw, events, cflags, n + 1); if (has_branch_stack(event)) { @@ -2031,13 +2033,13 @@ static int power_pmu_event_init(struct perf_event *event) event->attr.branch_sample_type); if (bhrb_filter == -1) { - put_cpu_var(cpu_hw_events); + local_irq_restore(irq_flags); return -EOPNOTSUPP; } cpuhw->bhrb_filter = bhrb_filter; } - put_cpu_var(cpu_hw_events); + local_irq_restore(irq_flags); if (err) return -EINVAL; |