From: "Paul E. McKenney" <paul...@kernel.org> 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" <paul...@kernel.org> Signed-off-by: Neeraj Upadhyay <neeraj.upadh...@kernel.org> --- kernel/rcu/rcuscale.c | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c index 3269dd9c639f..5087ca7062d9 100644 --- a/kernel/rcu/rcuscale.c +++ b/kernel/rcu/rcuscale.c @@ -39,6 +39,7 @@ #include <linux/torture.h> #include <linux/vmalloc.h> #include <linux/rcupdate_trace.h> +#include <linux/sched/debug.h> #include "rcu.h" @@ -111,6 +112,7 @@ static struct task_struct **reader_tasks; static struct task_struct *shutdown_task; static u64 **writer_durations; +static bool *writer_done; static int *writer_n_durations; static atomic_t n_rcu_scale_reader_started; static atomic_t n_rcu_scale_writer_started; @@ -524,6 +526,7 @@ rcu_scale_writer(void *arg) started = true; if (!done && i >= MIN_MEAS && time_after(jiffies, jdone)) { done = true; + WRITE_ONCE(writer_done[me], true); sched_set_normal(current, 0); pr_alert("%s%s rcu_scale_writer %ld has %d measurements\n", scale_type, SCALE_FLAG, me, MIN_MEAS); @@ -549,6 +552,19 @@ rcu_scale_writer(void *arg) if (done && !alldone && atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters) 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) i++; rcu_scale_wait_shutdown(); @@ -921,6 +937,8 @@ rcu_scale_cleanup(void) kfree(writer_tasks); kfree(writer_durations); kfree(writer_n_durations); + kfree(writer_done); + writer_done = NULL; } /* Do torture-type-specific cleanup operations. */ @@ -1015,10 +1033,11 @@ rcu_scale_init(void) } while (atomic_read(&n_rcu_scale_reader_started) < nrealreaders) 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_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"); firsterr = -ENOMEM; goto unwind; -- 2.40.1