| Message ID | 1606814880-1720-1-git-send-email-atrajeev@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | f66de7ac4849eb42a7b18e26b8ee49e08130fd27 |
| Headers | show |
| Series | powerpc/perf: Invoke per-CPU variable access with disabled interrupts | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (78c312324391ee996944e1196123b0060888e189) |
| snowpatch_ozlabs/build-ppc64le | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64be | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
| snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 33 lines checked |
| snowpatch_ozlabs/needsstable | success | Patch has no Fixes tags |
On Tue, 1 Dec 2020 04:28:00 -0500, Athira Rajeev wrote: > 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. > > [...] Applied to powerpc/next. [1/1] powerpc/perf: Invoke per-CPU variable access with disabled interrupts https://git.kernel.org/powerpc/c/f66de7ac4849eb42a7b18e26b8ee49e08130fd27 cheers
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c index 3c8c6ce..e38648f0 100644 --- a/arch/powerpc/perf/core-book3s.c +++ b/arch/powerpc/perf/core-book3s.c @@ -1909,7 +1909,7 @@ 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]; @@ -2017,7 +2017,9 @@ 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)) { @@ -2028,13 +2030,13 @@ 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;
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> --- arch/powerpc/perf/core-book3s.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)