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https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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fc18380fb9
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.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.