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deaff8b659
Intel PT decoding walks the object code to reconstruct the trace. A jump label change during tracing causes decoding errors. The "Enable close-on-exec flag on perf file descriptor" patch caused there to be always a jump label change. It was found that using a per-cpu context instead of a per-thread context for the probe of the close-on-exec feature, made the problem go away. Signed-off-by: Adrian Hunter <adrian.hunter@intel.com> Cc: David Ahern <dsahern@gmail.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@gmail.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Link: http://lkml.kernel.org/r/1406035081-14301-2-git-send-email-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
62 lines
1.2 KiB
C
62 lines
1.2 KiB
C
#include <sched.h>
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#include "util.h"
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#include "../perf.h"
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#include "cloexec.h"
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#include "asm/bug.h"
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static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
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static int perf_flag_probe(void)
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{
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/* use 'safest' configuration as used in perf_evsel__fallback() */
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struct perf_event_attr attr = {
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.type = PERF_COUNT_SW_CPU_CLOCK,
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.config = PERF_COUNT_SW_CPU_CLOCK,
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};
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int fd;
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int err;
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int cpu = sched_getcpu();
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if (cpu < 0)
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cpu = 0;
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/* check cloexec flag */
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fd = sys_perf_event_open(&attr, -1, cpu, -1,
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PERF_FLAG_FD_CLOEXEC);
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err = errno;
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if (fd >= 0) {
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close(fd);
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return 1;
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}
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WARN_ONCE(err != EINVAL,
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"perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
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err, strerror(err));
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/* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
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fd = sys_perf_event_open(&attr, -1, cpu, -1, 0);
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err = errno;
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if (WARN_ONCE(fd < 0,
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"perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
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err, strerror(err)))
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return -1;
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close(fd);
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return 0;
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}
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unsigned long perf_event_open_cloexec_flag(void)
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{
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static bool probed;
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if (!probed) {
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if (perf_flag_probe() <= 0)
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flag = 0;
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probed = true;
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}
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return flag;
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}
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