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rcuscale: Dump stacks of stalled rcu_scale_writer() instances

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This commit improves debuggability by dumping the stacks of
rcu_scale_writer() instances that have not completed in a reasonable
timeframe.  These stacks are dumped remotely, but they will be accurate
in the thus-far common case where the stalled rcu_scale_writer() instances
are blocked.

[ paulmck: Apply kernel test robot feedback. ]

Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
This commit is contained in:
Paul E. McKenney 2024-08-01 17:42:59 -07:00 committed by Neeraj Upadhyay
parent ea793764b5
commit 42a8a2695c
1 changed files with 21 additions and 2 deletions
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23
kernel/rcu/rcuscale.c
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@ -39,6 +39,7 @@
#include <linux/torture.h> #include <linux/torture.h>
#include <linux/vmalloc.h> #include <linux/vmalloc.h>
#include <linux/rcupdate_trace.h> #include <linux/rcupdate_trace.h>
#include <linux/sched/debug.h>
#include "rcu.h" #include "rcu.h"
@ -111,6 +112,7 @@ static struct task_struct **reader_tasks;
static struct task_struct *shutdown_task; static struct task_struct *shutdown_task;
static u64 **writer_durations; static u64 **writer_durations;
static bool *writer_done;
static int *writer_n_durations; static int *writer_n_durations;
static atomic_t n_rcu_scale_reader_started; static atomic_t n_rcu_scale_reader_started;
static atomic_t n_rcu_scale_writer_started; static atomic_t n_rcu_scale_writer_started;
@ -524,6 +526,7 @@ retry:
started = true; started = true;
if (!done && i >= MIN_MEAS && time_after(jiffies, jdone)) { if (!done && i >= MIN_MEAS && time_after(jiffies, jdone)) {
done = true; done = true;
WRITE_ONCE(writer_done[me], true);
sched_set_normal(current, 0); sched_set_normal(current, 0);
pr_alert("%s%s rcu_scale_writer %ld has %d measurements\n", pr_alert("%s%s rcu_scale_writer %ld has %d measurements\n",
scale_type, SCALE_FLAG, me, MIN_MEAS); scale_type, SCALE_FLAG, me, MIN_MEAS);
@ -549,6 +552,19 @@ retry:
if (done && !alldone && if (done && !alldone &&
atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters) atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters)
alldone = true; alldone = true;
if (done && !alldone && time_after(jiffies, jdone + HZ * 60)) {
static atomic_t dumped;
int i;
if (!atomic_xchg(&dumped, 1)) {
for (i = 0; i < nrealwriters; i++) {
if (writer_done[i])
continue;
pr_info("%s: Task %ld flags writer %d:\n", __func__, me, i);
sched_show_task(writer_tasks[i]);
}
}
}
if (started && !alldone && i < MAX_MEAS - 1) if (started && !alldone && i < MAX_MEAS - 1)
i++; i++;
rcu_scale_wait_shutdown(); rcu_scale_wait_shutdown();
@ -921,6 +937,8 @@ rcu_scale_cleanup(void)
kfree(writer_tasks); kfree(writer_tasks);
kfree(writer_durations); kfree(writer_durations);
kfree(writer_n_durations); kfree(writer_n_durations);
kfree(writer_done);
writer_done = NULL;
} }
/* Do torture-type-specific cleanup operations. */ /* Do torture-type-specific cleanup operations. */
@ -1015,10 +1033,11 @@ rcu_scale_init(void)
} }
while (atomic_read(&n_rcu_scale_reader_started) < nrealreaders) while (atomic_read(&n_rcu_scale_reader_started) < nrealreaders)
schedule_timeout_uninterruptible(1); schedule_timeout_uninterruptible(1);
writer_tasks = kcalloc(nrealwriters, sizeof(reader_tasks[0]), GFP_KERNEL); writer_tasks = kcalloc(nrealwriters, sizeof(writer_tasks[0]), GFP_KERNEL);
writer_durations = kcalloc(nrealwriters, sizeof(*writer_durations), GFP_KERNEL); writer_durations = kcalloc(nrealwriters, sizeof(*writer_durations), GFP_KERNEL);
writer_n_durations = kcalloc(nrealwriters, sizeof(*writer_n_durations), GFP_KERNEL); writer_n_durations = kcalloc(nrealwriters, sizeof(*writer_n_durations), GFP_KERNEL);
if (!writer_tasks || !writer_durations || !writer_n_durations) { writer_done = kcalloc(nrealwriters, sizeof(writer_done[0]), GFP_KERNEL);
if (!writer_tasks || !writer_durations || !writer_n_durations || !writer_done) {
SCALEOUT_ERRSTRING("out of memory"); SCALEOUT_ERRSTRING("out of memory");
firsterr = -ENOMEM; firsterr = -ENOMEM;
goto unwind; goto unwind;