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| author | Alexander Shishkin <alexander.shishkin@linux.intel.com> | 2015-04-21 16:16:16 +0300 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-05-27 10:17:47 +0300 |
| commit | 5b1dbd17c0dee679b154ce47f534677b7e0f7ad6 (patch) | |
| tree | ce5533853497f07eddd5b47531f4d99aad1e3312 /arch/x86 | |
| parent | cf302bfdf3039853fce812ae1ffd0ac24f5b468f (diff) | |
| download | linux-5b1dbd17c0dee679b154ce47f534677b7e0f7ad6.tar.xz | |
perf/x86/intel/pt: Document pt_buffer_reset_offsets()
Currently, the description of pt_buffer_reset_offsets() lacks information
about its calling constraints and ordering with regards to other buffer
management functions.
Add a clarification about when this function has to be called.
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: acme@infradead.org
Cc: adrian.hunter@intel.com
Cc: hpa@zytor.com
Link: http://lkml.kernel.org/r/1429622177-22843-5-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kernel/cpu/perf_event_intel_pt.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/perf_event_intel_pt.c b/arch/x86/kernel/cpu/perf_event_intel_pt.c index b2746eafa0cd..40ba5e4312d4 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_pt.c +++ b/arch/x86/kernel/cpu/perf_event_intel_pt.c @@ -705,7 +705,14 @@ static void pt_buffer_setup_topa_index(struct pt_buffer *buf) * @head: Write pointer (aux_head) from AUX buffer. * * Find the ToPA table and entry corresponding to given @head and set buffer's - * "current" pointers accordingly. + * "current" pointers accordingly. This is done after we have obtained the + * current aux_head position from a successful call to perf_aux_output_begin() + * to make sure the hardware is writing to the right place. + * + * This function modifies buf::{cur,cur_idx,output_off} that will be programmed + * into PT msrs when the tracing is enabled and buf::head and buf::data_size, + * which are used to determine INT and STOP markers' locations by a subsequent + * call to pt_buffer_reset_markers(). */ static void pt_buffer_reset_offsets(struct pt_buffer *buf, unsigned long head) { |