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Groups > linux.kernel > #1234495
| From | Arnaldo Carvalho de Melo <acme@kernel.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH 14/39] perf intel-pt: Fix potential loop forever |
| Date | 2015-09-28 23:20 +0200 |
| Message-ID | <qdO05-2Tc-75@gated-at.bofh.it> (permalink) |
| References | <qdNQm-2GE-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
From: Adrian Hunter <adrian.hunter@intel.com>
TSC packets contain only 7 bytes of TSC. The 8th byte is assumed to
change so infrequently that its value can be inferred. However the
logic must cater for a 7 byte wraparound, which it does by adding 1 to
the top byte.
The existing code was doing that with a while loop even though the
addition should only need to be done once. That logic won't work (will
loop forever) if TSC wraps around at the 8th byte. Theoretically that
would take at least 10 years, unless something else went wrong.
And what else could go wrong. Well, if the chunks of trace data are
processed out of order, it will make it look like the 7-byte TSC has
gone backwards (i.e. wrapped). If that happens 256 times then stuck in
the while loop it will be.
Fix that by getting rid of the unnecessary while loop.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1443186956-18718-4-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/util/intel-pt-decoder/intel-pt-decoder.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
index 22ba50224319..9409d014b46c 100644
--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
@@ -650,7 +650,7 @@ static int intel_pt_calc_cyc_cb(struct intel_pt_pkt_info *pkt_info)
if (data->from_mtc && timestamp < data->timestamp &&
data->timestamp - timestamp < decoder->tsc_slip)
return 1;
- while (timestamp < data->timestamp)
+ if (timestamp < data->timestamp)
timestamp += (1ULL << 56);
if (pkt_info->last_packet_type != INTEL_PT_CYC) {
if (data->from_mtc)
@@ -1191,7 +1191,7 @@ static void intel_pt_calc_tsc_timestamp(struct intel_pt_decoder *decoder)
timestamp);
timestamp = decoder->timestamp;
}
- while (timestamp < decoder->timestamp) {
+ if (timestamp < decoder->timestamp) {
intel_pt_log_to("Wraparound timestamp", timestamp);
timestamp += (1ULL << 56);
decoder->tsc_timestamp = timestamp;
--
2.1.0
--
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[GIT PULL 00/39] perf/core improvements and fixes Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:10 +0200 [PATCH 06/39] tools build: Add test for missing include Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:10 +0200 [PATCH 02/39] perf hists browser: Use the map to determine if a DSO is being used as a kernel Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:10 +0200 [PATCH 20/39] perf report: Adjust sample type validation for synthesized branch stacks Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:10 +0200 [PATCH 37/39] perf tools: Show proper error message for wrong terms of hw/sw events Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 31/39] perf evlist: Add perf_evlist__id2evsel_strict() Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 15/39] perf intel-pt: Make logging slightly more efficient Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 26/39] perf report: Make max_stack value allow for synthesized callchains Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 27/39] perf hists: Allow for max_stack greater than PERF_MAX_STACK_DEPTH Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 34/39] perf inject: Add --strip option to strip out non-synthesized events Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 29/39] perf scripting python: Allow for max_stack greater than PERF_MAX_STACK_DEPTH Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 01/39] perf top: Filter symbols based on __map__is_kernel(map) Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 03/39] perf tools: Use __map__is_kernel() when synthesizing kernel module mmap records Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 13/39] perf report: Fix sample type validation for synthesized callchains Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 32/39] perf evlist: Add perf_evlist__remove() Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 30/39] perf script: Make scripting_max_stack value allow for synthesized callchains Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 10/39] perf tools: Rename the 'single_dep' target to 'prepare' Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 11/39] tools build: Build fixdep helper from perf and basic libs Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 04/39] tools lib api fs: Store tracing mountpoint for better error message Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 14/39] perf intel-pt: Fix potential loop forever Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 07/39] tools build: Add fixdep dependency helper Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 35/39] perf intel-pt: Add mispred-all config option to aid use with autofdo Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:20 +0200 [PATCH 28/39] perf script: Add a setting for maximum stack depth Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:30 +0200 [PATCH 24/39] perf intel-pt: Move branch filter logic Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:30 +0200 [PATCH 23/39] perf inject: Set branch stack feature flag when synthesizing branch stacks Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:30 +0200 [PATCH 33/39] perf inject: Remove more aux-related stuff when processing instruction traces Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:30 +0200 [PATCH 18/39] perf tools: Add more documentation to export-to-postgresql.py script Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:30 +0200 [PATCH 17/39] perf session: Warn when AUX data has been lost Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:30 +0200 [PATCH 16/39] perf script: Allow time to be displayed in nanoseconds Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:30 +0200 [PATCH 25/39] perf intel-pt: Support generating branch stack Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:30 +0200 [PATCH 21/39] perf report: Also do default setup for synthesized branch stacks Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:30 +0200 [PATCH 22/39] perf report: Skip events with null branch stacks Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:30 +0200 [PATCH 05/39] tools build: Add Makefile.include Arnaldo Carvalho de Melo <acme@kernel.org> - 2015-09-28 23:30 +0200 Re: [GIT PULL 00/39] perf/core improvements and fixes Ingo Molnar <mingo@kernel.org> - 2015-09-29 09:50 +0200
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