diff options
| author | Adrian Hunter <adrian.hunter@intel.com> | 2024-07-15 19:07:00 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2024-07-29 12:16:24 +0200 |
| commit | d92792a4b26e50b96ab734cbe203d8a4c932a7a9 (patch) | |
| tree | 57a7a5891b46a2db0e4dc4a08f94115528114096 /arch/x86/events/intel | |
| parent | b1d0e15c8725d21a73c22c099418a63940261041 (diff) | |
perf/x86/intel/pt: Fix sampling synchronization
pt_event_snapshot_aux() uses pt->handle_nmi to determine if tracing
needs to be stopped, however tracing can still be going because
pt->handle_nmi is set to zero before tracing is stopped in pt_event_stop,
whereas pt_event_snapshot_aux() requires that tracing must be stopped in
order to copy a sample of trace from the buffer.
Instead call pt_config_stop() always, which anyway checks config for
RTIT_CTL_TRACEEN and does nothing if it is already clear.
Note pt_event_snapshot_aux() can continue to use pt->handle_nmi to
determine if the trace needs to be restarted afterwards.
Fixes: 25e8920b301c ("perf/x86/intel/pt: Add sampling support")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20240715160712.127117-2-adrian.hunter@intel.com
Diffstat (limited to 'arch/x86/events/intel')
| -rw-r--r-- | arch/x86/events/intel/pt.c | 15 |
1 files changed, 7 insertions, 8 deletions
diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c index b4aa8daa4773..2959970dd10e 100644 --- a/arch/x86/events/intel/pt.c +++ b/arch/x86/events/intel/pt.c @@ -1606,6 +1606,7 @@ static void pt_event_stop(struct perf_event *event, int mode) * see comment in intel_pt_interrupt(). */ WRITE_ONCE(pt->handle_nmi, 0); + barrier(); pt_config_stop(event); @@ -1657,11 +1658,10 @@ static long pt_event_snapshot_aux(struct perf_event *event, return 0; /* - * Here, handle_nmi tells us if the tracing is on + * There is no PT interrupt in this mode, so stop the trace and it will + * remain stopped while the buffer is copied. */ - if (READ_ONCE(pt->handle_nmi)) - pt_config_stop(event); - + pt_config_stop(event); pt_read_offset(buf); pt_update_head(pt); @@ -1673,11 +1673,10 @@ static long pt_event_snapshot_aux(struct perf_event *event, ret = perf_output_copy_aux(&pt->handle, handle, from, to); /* - * If the tracing was on when we turned up, restart it. - * Compiler barrier not needed as we couldn't have been - * preempted by anything that touches pt->handle_nmi. + * Here, handle_nmi tells us if the tracing was on. + * If the tracing was on, restart it. */ - if (pt->handle_nmi) + if (READ_ONCE(pt->handle_nmi)) pt_config_start(event); return ret; |