diff options
| author | Gabriele Monaco <gmonaco@redhat.com> | 2025-07-28 15:50:17 +0200 |
|---|---|---|
| committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2025-07-28 16:47:34 -0400 |
| commit | 9d475d80c93735f0f336b34a8e2c22beea6145ab (patch) | |
| tree | 8f5d7bcb14fecbe9b060d2bebe1cfaf917a974cf /kernel/trace | |
| parent | 79de661707a4a2dc695fd3e00529a14b4f5ec50d (diff) | |
rv: Retry when da monitor detects race conditions
DA monitor can be accessed from multiple cores simultaneously, this is
likely, for instance when dealing with per-task monitors reacting on
events that do not always occur on the CPU where the task is running.
This can cause race conditions where two events change the next state
and we see inconsistent values. E.g.:
[62] event_srs: 27: sleepable x sched_wakeup -> running (final)
[63] event_srs: 27: sleepable x sched_set_state_sleepable -> sleepable
[63] error_srs: 27: event sched_switch_suspend not expected in the state running
In this case the monitor fails because the event on CPU 62 wins against
the one on CPU 63, although the correct state should have been
sleepable, since the task get suspended.
Detect if the current state was modified by using try_cmpxchg while
storing the next value. If it was, try again reading the current state.
After a maximum number of failed retries, react by calling a special
tracepoint, print on the console and reset the monitor.
Remove the functions da_monitor_curr_state() and da_monitor_set_state()
as they only hide the underlying implementation in this case.
Monitors where this type of condition can occur must be able to account
for racing events in any possible order, as we cannot know the winner.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Tomas Glozar <tglozar@redhat.com>
Cc: Juri Lelli <jlelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/20250728135022.255578-6-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Reviewed-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
| -rw-r--r-- | kernel/trace/rv/Kconfig | 5 | ||||
| -rw-r--r-- | kernel/trace/rv/rv_trace.h | 24 |
2 files changed, 29 insertions, 0 deletions
diff --git a/kernel/trace/rv/Kconfig b/kernel/trace/rv/Kconfig index 26017378f79b..34164eb4ec91 100644 --- a/kernel/trace/rv/Kconfig +++ b/kernel/trace/rv/Kconfig @@ -3,12 +3,17 @@ config RV_MON_EVENTS bool +config RV_MON_MAINTENANCE_EVENTS + bool + config DA_MON_EVENTS_IMPLICIT select RV_MON_EVENTS + select RV_MON_MAINTENANCE_EVENTS bool config DA_MON_EVENTS_ID select RV_MON_EVENTS + select RV_MON_MAINTENANCE_EVENTS bool config LTL_MON_EVENTS_ID diff --git a/kernel/trace/rv/rv_trace.h b/kernel/trace/rv/rv_trace.h index d38e0d3abdfd..3af46cd185b3 100644 --- a/kernel/trace/rv/rv_trace.h +++ b/kernel/trace/rv/rv_trace.h @@ -176,6 +176,30 @@ DECLARE_EVENT_CLASS(error_ltl_monitor_id, #include <monitors/sleep/sleep_trace.h> // Add new monitors based on CONFIG_LTL_MON_EVENTS_ID here #endif /* CONFIG_LTL_MON_EVENTS_ID */ + +#ifdef CONFIG_RV_MON_MAINTENANCE_EVENTS +/* Tracepoint useful for monitors development, currenly only used in DA */ +TRACE_EVENT(rv_retries_error, + + TP_PROTO(char *name, char *event), + + TP_ARGS(name, event), + + TP_STRUCT__entry( + __string( name, name ) + __string( event, event ) + ), + + TP_fast_assign( + __assign_str(name); + __assign_str(event); + ), + + TP_printk(__stringify(MAX_DA_RETRY_RACING_EVENTS) + " retries reached for event %s, resetting monitor %s", + __get_str(event), __get_str(name)) +); +#endif /* CONFIG_RV_MON_MAINTENANCE_EVENTS */ #endif /* _TRACE_RV_H */ /* This part must be outside protection */ |