korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2024-11-16 08:44:21 +08:00
Code Issues Packages Projects Releases Wiki Activity

perf, x86: Fix accidentally ack'ing a second event on intel perf counter

Browse Source 
During testing of a patch to stop having the perf subsytem
swallow nmis, it was uncovered that Nehalem boxes were randomly
getting unknown nmis when using the perf tool.

Moving the ack'ing of the PMI closer to when we get the status
allows the hardware to properly re-set the PMU bit signaling
another PMI was triggered during the processing of the first
PMI.  This allows the new logic for dealing with the
shortcomings of multiple PMIs to handle the extra NMI by
'eat'ing it later.

Now one can wonder why are we getting a second PMI when we
disable all the PMUs in the begining of the NMI handler to
prevent such a case, for that I do not know.  But I know the fix
below helps deal with this quirk.

Tested on multiple Nehalems where the problem was occuring.
With the patch, the code now loops a second time to handle the
second PMI (whereas before it was not).

Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: peterz@infradead.org
Cc: robert.richter@amd.com
Cc: gorcunov@gmail.com
Cc: fweisbec@gmail.com
Cc: ying.huang@intel.com
Cc: ming.m.lin@intel.com
Cc: eranian@google.com
LKML-Reference: <1283454469-1909-2-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Don Zickus 2010-09-02 15:07:47 -04:00 committed by Ingo Molnar
parent b4c69d45c4
commit 2e556b5b32
1 changed files with 2 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/x86/kernel/cpu/perf_event_intel.c
View File

@ -712,7 +712,7 @@ static int intel_pmu_handle_irq(struct pt_regs *regs)
struct perf_sample_data data;
struct cpu_hw_events *cpuc;
int bit, loops;
u64 ack, status;
u64 status;
perf_sample_data_init(&data, 0);
@ -728,6 +728,7 @@ static int intel_pmu_handle_irq(struct pt_regs *regs)
loops = 0;
again:
intel_pmu_ack_status(status);
if (++loops > 100) {
WARN_ONCE(1, "perfevents: irq loop stuck!\n");
perf_event_print_debug();
@ -736,7 +737,6 @@ again:
}
inc_irq_stat(apic_perf_irqs);
ack = status;
intel_pmu_lbr_read();
@ -761,8 +761,6 @@ again:
x86_pmu_stop(event);
}
intel_pmu_ack_status(ack);
/*
* Repeat if there is more work to be done:
*/