6.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Tejun Heo tj@kernel.org
[ Upstream commit 2a1b02bcba78f8498ab00d6142e1238d85b01591 ]
Currently, worker ID formatting is open coded in create_worker(), init_rescuer() and worker_thread() (for %WORKER_DIE case). The formatted ID is saved into task->comm and wq_worker_comm() uses it as the base name to append extra information to when generating the name to be shown to userspace.
However, TASK_COMM_LEN is only 16 leading to badly truncated names for rescuers. For example, the rescuer for the inet_frag_wq workqueue becomes:
$ ps -ef | grep '[k]worker/R-inet' root 483 2 0 Apr26 ? 00:00:00 [kworker/R-inet_]
Even for non-rescue workers, it's easy to run over 15 characters on moderately large machines.
Fit it by consolidating worker ID formatting into a new helper format_worker_id() and calling it from wq_worker_comm() to obtain the untruncated worker ID string.
$ ps -ef | grep '[k]worker/R-inet' root 60 2 0 12:10 ? 00:00:00 [kworker/R-inet_frag_wq]
Signed-off-by: Tejun Heo tj@kernel.org Reported-and-tested-by: Jan Engelhardt jengelh@inai.de Suggested-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/workqueue.c | 51 ++++++++++++++++++++++++++++++---------------- 1 file changed, 34 insertions(+), 17 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index d2dbe099286b9..7634fc32ee05a 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -124,6 +124,7 @@ enum wq_internal_consts { HIGHPRI_NICE_LEVEL = MIN_NICE,
WQ_NAME_LEN = 32, + WORKER_ID_LEN = 10 + WQ_NAME_LEN, /* "kworker/R-" + WQ_NAME_LEN */ };
/* @@ -2778,6 +2779,26 @@ static void worker_detach_from_pool(struct worker *worker) complete(detach_completion); }
+static int format_worker_id(char *buf, size_t size, struct worker *worker, + struct worker_pool *pool) +{ + if (worker->rescue_wq) + return scnprintf(buf, size, "kworker/R-%s", + worker->rescue_wq->name); + + if (pool) { + if (pool->cpu >= 0) + return scnprintf(buf, size, "kworker/%d:%d%s", + pool->cpu, worker->id, + pool->attrs->nice < 0 ? "H" : ""); + else + return scnprintf(buf, size, "kworker/u%d:%d", + pool->id, worker->id); + } else { + return scnprintf(buf, size, "kworker/dying"); + } +} + /** * create_worker - create a new workqueue worker * @pool: pool the new worker will belong to @@ -2794,7 +2815,6 @@ static struct worker *create_worker(struct worker_pool *pool) { struct worker *worker; int id; - char id_buf[23];
/* ID is needed to determine kthread name */ id = ida_alloc(&pool->worker_ida, GFP_KERNEL); @@ -2813,17 +2833,14 @@ static struct worker *create_worker(struct worker_pool *pool) worker->id = id;
if (!(pool->flags & POOL_BH)) { - if (pool->cpu >= 0) - snprintf(id_buf, sizeof(id_buf), "%d:%d%s", pool->cpu, id, - pool->attrs->nice < 0 ? "H" : ""); - else - snprintf(id_buf, sizeof(id_buf), "u%d:%d", pool->id, id); + char id_buf[WORKER_ID_LEN];
+ format_worker_id(id_buf, sizeof(id_buf), worker, pool); worker->task = kthread_create_on_node(worker_thread, worker, - pool->node, "kworker/%s", id_buf); + pool->node, "%s", id_buf); if (IS_ERR(worker->task)) { if (PTR_ERR(worker->task) == -EINTR) { - pr_err("workqueue: Interrupted when creating a worker thread "kworker/%s"\n", + pr_err("workqueue: Interrupted when creating a worker thread "%s"\n", id_buf); } else { pr_err_once("workqueue: Failed to create a worker thread: %pe", @@ -3386,7 +3403,6 @@ static int worker_thread(void *__worker) raw_spin_unlock_irq(&pool->lock); set_pf_worker(false);
- set_task_comm(worker->task, "kworker/dying"); ida_free(&pool->worker_ida, worker->id); worker_detach_from_pool(worker); WARN_ON_ONCE(!list_empty(&worker->entry)); @@ -5430,6 +5446,7 @@ static int wq_clamp_max_active(int max_active, unsigned int flags, static int init_rescuer(struct workqueue_struct *wq) { struct worker *rescuer; + char id_buf[WORKER_ID_LEN]; int ret;
if (!(wq->flags & WQ_MEM_RECLAIM)) @@ -5443,7 +5460,9 @@ static int init_rescuer(struct workqueue_struct *wq) }
rescuer->rescue_wq = wq; - rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R-%s", wq->name); + format_worker_id(id_buf, sizeof(id_buf), rescuer, NULL); + + rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", id_buf); if (IS_ERR(rescuer->task)) { ret = PTR_ERR(rescuer->task); pr_err("workqueue: Failed to create a rescuer kthread for wq "%s": %pe", @@ -6272,19 +6291,15 @@ void show_freezable_workqueues(void) /* used to show worker information through /proc/PID/{comm,stat,status} */ void wq_worker_comm(char *buf, size_t size, struct task_struct *task) { - int off; - - /* always show the actual comm */ - off = strscpy(buf, task->comm, size); - if (off < 0) - return; - /* stabilize PF_WQ_WORKER and worker pool association */ mutex_lock(&wq_pool_attach_mutex);
if (task->flags & PF_WQ_WORKER) { struct worker *worker = kthread_data(task); struct worker_pool *pool = worker->pool; + int off; + + off = format_worker_id(buf, size, worker, pool);
if (pool) { raw_spin_lock_irq(&pool->lock); @@ -6303,6 +6318,8 @@ void wq_worker_comm(char *buf, size_t size, struct task_struct *task) } raw_spin_unlock_irq(&pool->lock); } + } else { + strscpy(buf, task->comm, size); }
mutex_unlock(&wq_pool_attach_mutex);