From: Jens Axboe <axboe@kernel.dk> mainline inclusion from mainline-v6.7-rc2 commit a0d45c3f596be53c1bd8822a1984532d14fdcea9 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IC6ES1 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- A previous commit added a trylock for getting the SQPOLL thread info via fdinfo, but this introduced a regression where we often fail to get it if the thread is busy. For that case, we end up not printing the current CPU and PID info. Rather than rely on this lock, just print the pid we already stored in the io_sq_data struct, and ensure we update the current CPU every time we've slept or potentially rescheduled. The latter won't potentially be 100% accurate, but that wasn't the case before either as the task can get migrated at any time unless it has been pinned at creation time. We retain keeping the io_sq_data dereference inside the ctx->uring_lock, as it has always been, as destruction of the thread and data happen below that. We could make this RCU safe, but there's little point in doing that. With this, we always print the last valid information we had, rather than have spurious outputs with missing information. Fixes: 7644b1a1c9a7 ("io_uring/fdinfo: lock SQ thread while retrieving thread cpu/pid") Signed-off-by: Jens Axboe <axboe@kernel.dk> Conflicts: io_uring/fdinfo.c io_uring/sqpoll.c [Commit a4ad4f748ea9 ("io_uring: move fdinfo helpers to its own file") move io_uring_show_fdinfo from io_uring.c to fdinfo.c; commit 17437f311490 ("io_uring: move SQPOLL related handling into its own file") move io_sqd_handle_event/io_sq_thread from io_uring.c to sqpoll.c] Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com> --- io_uring/io_uring.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index bdbd8fe36773..fa0370fdb1d6 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -7523,6 +7523,7 @@ static bool io_sqd_handle_event(struct io_sq_data *sqd) did_sig = get_signal(&ksig); cond_resched(); mutex_lock(&sqd->lock); + sqd->sq_cpu = raw_smp_processor_id(); } return did_sig || test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state); } @@ -7538,10 +7539,15 @@ static int io_sq_thread(void *data) snprintf(buf, sizeof(buf), "iou-sqp-%d", sqd->task_pid); set_task_comm(current, buf); - if (sqd->sq_cpu != -1) + /* reset to our pid after we've set task_comm, for fdinfo */ + sqd->task_pid = current->pid; + + if (sqd->sq_cpu != -1) { set_cpus_allowed_ptr(current, cpumask_of(sqd->sq_cpu)); - else + } else { set_cpus_allowed_ptr(current, cpu_online_mask); + sqd->sq_cpu = raw_smp_processor_id(); + } mutex_lock(&sqd->lock); while (1) { @@ -7565,6 +7571,7 @@ static int io_sq_thread(void *data) if (sqt_spin || !time_after(jiffies, timeout)) { cond_resched(); + sqd->sq_cpu = raw_smp_processor_id(); if (sqt_spin) timeout = jiffies + sqd->sq_thread_idle; continue; @@ -7592,6 +7599,7 @@ static int io_sq_thread(void *data) mutex_unlock(&sqd->lock); schedule(); mutex_lock(&sqd->lock); + sqd->sq_cpu = raw_smp_processor_id(); } list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) io_ring_clear_wakeup_flag(ctx); @@ -10054,13 +10062,8 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m) if (has_lock && (ctx->flags & IORING_SETUP_SQPOLL)) { struct io_sq_data *sq = ctx->sq_data; - if (mutex_trylock(&sq->lock)) { - if (sq->thread) { - sq_pid = task_pid_nr(sq->thread); - sq_cpu = task_cpu(sq->thread); - } - mutex_unlock(&sq->lock); - } + sq_pid = sq->task_pid; + sq_cpu = sq->sq_cpu; } seq_printf(m, "SqThread:\t%d\n", sq_pid); -- 2.31.1