workqueue: Set worker->desc to workqueue name by default

Work functions can use set_worker_desc() to improve the visibility of
what the worker task is doing.  Currently, the desc field is unset at
the beginning of each execution and there is a separate field to track
the field is set during the current execution.

Instead of leaving empty till desc is set, worker->desc can be used to
remember the last workqueue the worker worked on by default and users
that use set_worker_desc() can override it to something more
informative as necessary.

This simplifies desc handling and helps tracking the last workqueue
that the worker exected on to improve visibility.

Signed-off-by: Tejun Heo <tj@kernel.org>

2 files changed, 10 insertions, 12 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 2fde50f8221b..3fbe0076492c 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2088,6 +2088,12 @@ __acquires(&pool->lock)
         worker->current_pwq = pwq;
         work_color = get_work_color(work);
 
+        /*
+         * Record wq name for cmdline and debug reporting, may get
+         * overridden through set_worker_desc().
+         */
+        strscpy(worker->desc, pwq->wq->name, WORKER_DESC_LEN);
+
         list_del_init(&work->entry);
 
         /*
@@ -2183,7 +2189,6 @@ __acquires(&pool->lock)
         worker->current_work = NULL;
         worker->current_func = NULL;
         worker->current_pwq = NULL;
-        worker->desc_valid = false;
         pwq_dec_nr_in_flight(pwq, work_color);
 }
 
@@ -4346,7 +4351,6 @@ void set_worker_desc(const char *fmt, ...)
                 va_start(args, fmt);
                 vsnprintf(worker->desc, sizeof(worker->desc), fmt, args);
                 va_end(args);
-                worker->desc_valid = true;
         }
 }
 
@@ -4370,7 +4374,6 @@ void print_worker_info(const char *log_lvl, struct task_struct *task)
         char desc[WORKER_DESC_LEN] = { };
         struct pool_workqueue *pwq = NULL;
         struct workqueue_struct *wq = NULL;
-        bool desc_valid = false;
         struct worker *worker;
 
         if (!(task->flags & PF_WQ_WORKER))
@@ -4383,22 +4386,18 @@ void print_worker_info(const char *log_lvl, struct task_struct *task)
         worker = kthread_probe_data(task);
 
         /*
-         * Carefully copy the associated workqueue's workfn and name.  Keep
-         * the original last '\0' in case the original contains garbage.
+         * Carefully copy the associated workqueue's workfn, name and desc.
+         * Keep the original last '\0' in case the original is garbage.
          */
         probe_kernel_read(&fn, &worker->current_func, sizeof(fn));
         probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq));
         probe_kernel_read(&wq, &pwq->wq, sizeof(wq));
         probe_kernel_read(name, wq->name, sizeof(name) - 1);
-
-        /* copy worker description */
-        probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid));
-        if (desc_valid)
-                probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
+        probe_kernel_read(desc, worker->desc, sizeof(desc) - 1);
 
         if (fn || name[0] || desc[0]) {
                 printk("%sWorkqueue: %s %pf", log_lvl, name, fn);
-                if (desc[0])
+                if (strcmp(name, desc))
                         pr_cont(" (%s)", desc);
                 pr_cont("\n");
         }
diff --git a/kernel/workqueue_internal.h b/kernel/workqueue_internal.h
index 4a182e027207..66fbb5a9e633 100644
--- a/kernel/workqueue_internal.h
+++ b/kernel/workqueue_internal.h
@@ -31,7 +31,6 @@ struct worker {
         struct work_struct      *current_work;  /* L: work being processed */
         work_func_t             current_func;   /* L: current_work's fn */
         struct pool_workqueue   *current_pwq; /* L: current_work's pwq */
-        bool                    desc_valid;     /* ->desc is valid */
         struct list_head        scheduled;      /* L: scheduled works */
 
         /* 64 bytes boundary on 64bit, 32 on 32bit */