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| author | Neeraj Upadhyay <quic_neeraju@quicinc.com> | 2023-01-11 13:15:00 +0530 |
|---|---|---|
| committer | Joel Fernandes (Google) <joel@joelfernandes.org> | 2023-04-05 13:47:44 +0000 |
| commit | a4533cc0a59f0956e1b78e6013b75014b4857fce (patch) | |
| tree | 83b60ad1c8688477ab344627824310de6dd8baac /kernel/rcu | |
| parent | 7ea91307ad2dbdd15ed0b762a2d994f816039b9d (diff) | |
| download | linux-a4533cc0a59f0956e1b78e6013b75014b4857fce.tar.gz | |
rcu-tasks: Report stalls during synchronize_srcu() in rcu_tasks_postscan()
The call to synchronize_srcu() from rcu_tasks_postscan() can be stalled
by a task getting stuck in do_exit() between that function's calls to
exit_tasks_rcu_start() and exit_tasks_rcu_finish(). To ease diagnosis
of this situation, print a stall warning message every rcu_task_stall_info
period when rcu_tasks_postscan() is stalled.
[ paulmck: Adjust to handle CONFIG_SMP=n. ]
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Reported-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/rcu/20230111212736.GA1062057@paulmck-ThinkPad-P17-Gen-1/
Signed-off-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tasks.h | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index bfb5e1549f2b2..baf7ec178155a 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -139,6 +139,12 @@ static struct rcu_tasks rt_name = \ /* Track exiting tasks in order to allow them to be waited for. */ DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu); +#ifdef CONFIG_TASKS_RCU +/* Report delay in synchronize_srcu() completion in rcu_tasks_postscan(). */ +static void tasks_rcu_exit_srcu_stall(struct timer_list *unused); +static DEFINE_TIMER(tasks_rcu_exit_srcu_stall_timer, tasks_rcu_exit_srcu_stall); +#endif + /* Avoid IPIing CPUs early in the grace period. */ #define RCU_TASK_IPI_DELAY (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) ? HZ / 2 : 0) static int rcu_task_ipi_delay __read_mostly = RCU_TASK_IPI_DELAY; @@ -830,6 +836,13 @@ static void rcu_tasks_pertask(struct task_struct *t, struct list_head *hop) /* Processing between scanning taskslist and draining the holdout list. */ static void rcu_tasks_postscan(struct list_head *hop) { + int rtsi = READ_ONCE(rcu_task_stall_info); + + if (!IS_ENABLED(CONFIG_TINY_RCU)) { + tasks_rcu_exit_srcu_stall_timer.expires = jiffies + rtsi; + add_timer(&tasks_rcu_exit_srcu_stall_timer); + } + /* * Exiting tasks may escape the tasklist scan. Those are vulnerable * until their final schedule() with TASK_DEAD state. To cope with @@ -848,6 +861,9 @@ static void rcu_tasks_postscan(struct list_head *hop) * call to synchronize_rcu(). */ synchronize_srcu(&tasks_rcu_exit_srcu); + + if (!IS_ENABLED(CONFIG_TINY_RCU)) + del_timer_sync(&tasks_rcu_exit_srcu_stall_timer); } /* See if tasks are still holding out, complain if so. */ @@ -923,6 +939,21 @@ static void rcu_tasks_postgp(struct rcu_tasks *rtp) void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func); DEFINE_RCU_TASKS(rcu_tasks, rcu_tasks_wait_gp, call_rcu_tasks, "RCU Tasks"); +static void tasks_rcu_exit_srcu_stall(struct timer_list *unused) +{ +#ifndef CONFIG_TINY_RCU + int rtsi; + + rtsi = READ_ONCE(rcu_task_stall_info); + pr_info("%s: %s grace period number %lu (since boot) gp_state: %s is %lu jiffies old.\n", + __func__, rcu_tasks.kname, rcu_tasks.tasks_gp_seq, + tasks_gp_state_getname(&rcu_tasks), jiffies - rcu_tasks.gp_jiffies); + pr_info("Please check any exiting tasks stuck between calls to exit_tasks_rcu_start() and exit_tasks_rcu_finish()\n"); + tasks_rcu_exit_srcu_stall_timer.expires = jiffies + rtsi; + add_timer(&tasks_rcu_exit_srcu_stall_timer); +#endif // #ifndef CONFIG_TINY_RCU +} + /** * call_rcu_tasks() - Queue an RCU for invocation task-based grace period * @rhp: structure to be used for queueing the RCU updates. |