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Adrian Hunter authored
The kernel can release tasks while they are still running. This can result in a task having no tid, in which case perf records a tid of -1. Improve the perf script output in that case. Example: Before: # cat ./autoreap.c #include <sys/types.h> #include <unistd.h> #include <sys/wait.h> #include <signal.h> struct sigaction act = { .sa_handler = SIG_IGN, }; int main() { pid_t child; int status = 0; sigaction(SIGCHLD, &act, NULL); child = fork(); if (child == 0) return 123; wait(&status); return 0; } # gcc -o autoreap autoreap.c # ./perf record -a -e dummy --switch-events ./autoreap [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.948 MB perf.data ] # ./perf script --show-task-events --show-switch-events | grep -C2 'autoreap\|4294967295\|-1' swapper 0 [004] 18462.673613: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25189/25189 perf 25189 [004] 18462.673614: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0 autoreap 25189 [004] 18462.673800: PERF_RECORD_COMM exec: autoreap:25189/25189 autoreap 25189 [004] 18462.674042: PERF_RECORD_FORK(25191:25191):(25189:25189) autoreap 25189 [004] 18462.674050: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0 swapper 0 [004] 18462.674051: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 25189/25189 swapper 0 [005] 18462.674083: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25191/25191 autoreap 25191 [005] 18462.674084: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0 swapper 0 [003] 18462.674121: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 11/11 rcu_preempt 11 [003] 18462.674121: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0 rcu_preempt 11 [003] 18462.674124: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0 swapper 0 [003] 18462.674124: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11/11 autoreap 25191 [005] 18462.674138: PERF_RECORD_EXIT(25191:25191):(25189:25189) PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0 swapper 0 [005] 18462.674149: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 4294967295/4294967295 swapper 0 [004] 18462.674182: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25189/25189 autoreap 25189 [004] 18462.674183: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0 autoreap 25189 [004] 18462.674218: PERF_RECORD_EXIT(25189:25189):(25188:25188) autoreap 25189 [004] 18462.674225: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0 swapper 0 [004] 18462.674226: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 25189/25189 swapper 0 [007] 18462.674257: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25188/25188 After: # ./perf script --show-task-events --show-switch-events | grep -C2 'autoreap\|4294967295\|-1' swapper 0 [004] 18462.673613: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25189/25189 perf 25189 [004] 18462.673614: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0 autoreap 25189 [004] 18462.673800: PERF_RECORD_COMM exec: autoreap:25189/25189 autoreap 25189 [004] 18462.674042: PERF_RECORD_FORK(25191:25191):(25189:25189) autoreap 25189 [004] 18462.674050: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0 swapper 0 [004] 18462.674051: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 25189/25189 swapper 0 [005] 18462.674083: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25191/25191 autoreap 25191 [005] 18462.674084: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0 swapper 0 [003] 18462.674121: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 11/11 rcu_preempt 11 [003] 18462.674121: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0 rcu_preempt 11 [003] 18462.674124: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0 swapper 0 [003] 18462.674124: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11/11 autoreap 25191 [005] 18462.674138: PERF_RECORD_EXIT(25191:25191):(25189:25189) :-1 -1 [005] 18462.674149: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0 swapper 0 [005] 18462.674149: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: -1/-1 swapper 0 [004] 18462.674182: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25189/25189 autoreap 25189 [004] 18462.674183: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0 autoreap 25189 [004] 18462.674218: PERF_RECORD_EXIT(25189:25189):(25188:25188) autoreap 25189 [004] 18462.674225: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0 swapper 0 [004] 18462.674226: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 25189/25189 swapper 0 [007] 18462.674257: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25188/25188 Signed-off-by:Adrian Hunter <adrian.hunter@intel.com> Tested-by:
Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Yu-cheng Yu <yu-cheng.yu@intel.com> Link: http://lore.kernel.org/lkml/20200909084923.9096-2-adrian.hunter@intel.comSigned-off-by:
fc18380f
