[RFC PATCH] workqueue: Fix rescuer task's name truncated

[Wenchao Hao]

Task comm of task is limitted to 16, prefix "kworker/R-" is added for
rescuer worker's task, which cause most task name is truncated as
following:

root   81  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-xprti]
root   82  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-cfg80]
root   85  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-nfsio]
root   86  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-xfsal]
root   87  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-xfs_m]
root   88  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-acpi_]
root   93  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-iscsi]
root   95  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-scsi_]
root   97  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-scsi_]
root   99  0.0  0.0  0  0 ?   I<   11:18   0:00 [kworker/R-scsi_]

I want to fix this issue by split rescuer name to 2 part like other
kworker, the normal part is "kworker/R" which is set to task_struct's comm,
another part is wq->name which is added to kworker's desc. These 2 parts
would be merged in wq_worker_comm().

Fixes: b6a46f7263bd ("workqueue: Rename rescuer kworker")

Signed-off-by: Wenchao Hao <haowenchao2@xxxxxxxxxx>
---
 kernel/workqueue.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 0066c8f6c154..0ce9e8597a4d 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5430,7 +5430,7 @@ static int init_rescuer(struct workqueue_struct *wq)
 	}
 
 	rescuer->rescue_wq = wq;
-	rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R-%s", wq->name);
+	rescuer->task = kthread_create(rescuer_thread, rescuer, "kworker/R");
 	if (IS_ERR(rescuer->task)) {
 		ret = PTR_ERR(rescuer->task);
 		pr_err("workqueue: Failed to create a rescuer kthread for wq \"%s\": %pe",
@@ -5439,6 +5439,8 @@ static int init_rescuer(struct workqueue_struct *wq)
 		return ret;
 	}
 
+	snprintf(rescuer->desc, sizeof(rescuer->desc), "%s", wq->name);
+
 	wq->rescuer = rescuer;
 	if (wq->flags & WQ_UNBOUND)
 		kthread_bind_mask(rescuer->task, wq_unbound_cpumask);
@@ -6289,6 +6291,8 @@ void wq_worker_comm(char *buf, size_t size, struct task_struct *task)
 						  worker->desc);
 			}
 			raw_spin_unlock_irq(&pool->lock);
+		} else if (worker->desc[0] != '\0') {
+			scnprintf(buf + off, size - off, "-%s", worker->desc);
 		}
 	}
 
-- 
2.32.0