diff options
| author | Valentin Schneider <valentin.schneider@arm.com> | 2022-01-20 16:25:19 +0000 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-03-01 16:18:39 +0100 |
| commit | fa2c3254d7cfff5f7a916ab928a562d1165f17bb (patch) | |
| tree | 678cc10a62564212f526fc4a65ea345fde95794e /include/linux/sched.h | |
| parent | 49bef33e4b87b743495627a529029156c6e09530 (diff) | |
| download | lwn-fa2c3254d7cfff5f7a916ab928a562d1165f17bb.tar.gz lwn-fa2c3254d7cfff5f7a916ab928a562d1165f17bb.zip | |
sched/tracing: Don't re-read p->state when emitting sched_switch event
As of commit
c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu")
the following sequence becomes possible:
p->__state = TASK_INTERRUPTIBLE;
__schedule()
deactivate_task(p);
ttwu()
READ !p->on_rq
p->__state=TASK_WAKING
trace_sched_switch()
__trace_sched_switch_state()
task_state_index()
return 0;
TASK_WAKING isn't in TASK_REPORT, so the task appears as TASK_RUNNING in
the trace event.
Prevent this by pushing the value read from __schedule() down the trace
event.
Reported-by: Abhijeet Dharmapurikar <adharmap@quicinc.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20220120162520.570782-2-valentin.schneider@arm.com
Diffstat (limited to 'include/linux/sched.h')
| -rw-r--r-- | include/linux/sched.h | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index f00132e7ef6e..457c8a058b77 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1620,10 +1620,10 @@ static inline pid_t task_pgrp_nr(struct task_struct *tsk) #define TASK_REPORT_IDLE (TASK_REPORT + 1) #define TASK_REPORT_MAX (TASK_REPORT_IDLE << 1) -static inline unsigned int task_state_index(struct task_struct *tsk) +static inline unsigned int __task_state_index(unsigned int tsk_state, + unsigned int tsk_exit_state) { - unsigned int tsk_state = READ_ONCE(tsk->__state); - unsigned int state = (tsk_state | tsk->exit_state) & TASK_REPORT; + unsigned int state = (tsk_state | tsk_exit_state) & TASK_REPORT; BUILD_BUG_ON_NOT_POWER_OF_2(TASK_REPORT_MAX); @@ -1633,6 +1633,11 @@ static inline unsigned int task_state_index(struct task_struct *tsk) return fls(state); } +static inline unsigned int task_state_index(struct task_struct *tsk) +{ + return __task_state_index(READ_ONCE(tsk->__state), tsk->exit_state); +} + static inline char task_index_to_char(unsigned int state) { static const char state_char[] = "RSDTtXZPI"; |