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Daniel Bristot de Oliveira authored
[ Upstream commit 07485918 ] Currently, the sched:sched_switch tracepoint reports deadline tasks with priority -1. But when reading the trace via perf script I've got the following output: # ./d & # (d is a deadline task, see [1]) # perf record -e sched:sched_switch -a sleep 1 # perf script ... swapper 0 [000] 2146.962441: sched:sched_switch: swapper/0:0 [120] R ==> d:2593 [4294967295] d 2593 [000] 2146.972472: sched:sched_switch: d:2593 [4294967295] R ==> g:2590 [4294967295] The task d reports the wrong priority [4294967295]. This happens because the "int prio" is stored in an unsigned long long val. Although it is set as a %lld, as int is shorter than unsigned long long, trace_seq_printf prints it as a positive number. The fix is just to cast the val as an int, and print it as a %d, as in the sched:sched_switch tracepoint's "format". The output with the fix is: # ./d & # perf record -e sched:sched_switch -a sleep 1 # perf script ... swapper 0 [000] 4306.374037: sched:sched_switch: swapper/0:0 [120] R ==> d:10941 [-1] d 10941 [000] 4306.383823: sched:sched_switch: d:10941 [-1] R ==> swapper/0:0 [120] [1] d.c --- #include <stdio.h> #include <unistd.h> #include <sys/syscall.h> #include <linux/types.h> #include <linux/sched.h> struct sched_attr { __u32 size, sched_policy; __u64 sched_flags; __s32 sched_nice; __u32 sched_priority; __u64 sched_runtime, sched_deadline, sched_period; }; int sched_setattr(pid_t pid, const struct sched_attr *attr, unsigned int flags) { return syscall(__NR_sched_setattr, pid, attr, flags); } int main(void) { struct sched_attr attr = { .size = sizeof(attr), .sched_policy = SCHED_DEADLINE, /* This creates a 10ms/30ms reservation */ .sched_runtime = 10 * 1000 * 1000, .sched_period = attr.sched_deadline = 30 * 1000 * 1000, }; if (sched_setattr(0, &attr, 0) < 0) { perror("sched_setattr"); return -1; } for(;;); } --- Committer notes: Got the program from the provided URL, http://bristot.me/lkml/d.c, trimmed it and included in the cset log above, so that we have everything needed to test it in one place. Signed-off-by:
Daniel Bristot de Oliveira <bristot@redhat.com> Acked-by:
Steven Rostedt <rostedt@goodmis.org> Tested-by:
Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Daniel Bristot de Oliveira <bristot@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/866ef75bcebf670ae91c6a96daa63597ba981f0d.1483443552.git.bristot@redhat.comSigned-off-by:
Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by:
Sasha Levin <alexander.levin@verizon.com> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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