Messages in this thread Patch in this message | | | Date | Wed, 27 May 2015 03:08:18 -0700 | From | tip-bot for Alexander Shishkin <> | Subject | [tip:perf/core] perf/x86/intel/pt: Document pt_buffer_reset_offsets() |
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Commit-ID: 5b1dbd17c0dee679b154ce47f534677b7e0f7ad6 Gitweb: http://git.kernel.org/tip/5b1dbd17c0dee679b154ce47f534677b7e0f7ad6 Author: Alexander Shishkin <alexander.shishkin@linux.intel.com> AuthorDate: Tue, 21 Apr 2015 16:16:16 +0300 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Wed, 27 May 2015 09:17:47 +0200
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> --- arch/x86/kernel/cpu/perf_event_intel_pt.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_pt.c b/arch/x86/kernel/cpu/perf_event_intel_pt.c index b2746ea..40ba5e4 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) {
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