From: Tejun Heo tj@kernel.org
[ Upstream commit 1c270b79ce0b8290f146255ea9057243f6dd3c17 ]
__queue_work(), pwq_dec_nr_in_flight() and wq_adjust_max_active() were open-coding nr_active handling, which is fine given that the operations are trivial. However, the planned unbound nr_active update will make them more complicated, so let's move them into helpers.
- pwq_tryinc_nr_active() is added. It increments nr_active if under max_active limit and return a boolean indicating whether inc was successful. Note that the function is structured to accommodate future changes. __queue_work() is updated to use the new helper.
- pwq_activate_first_inactive() is updated to use pwq_tryinc_nr_active() and thus no longer assumes that nr_active is under max_active and returns a boolean to indicate whether a work item has been activated.
- wq_adjust_max_active() no longer tests directly whether a work item can be activated. Instead, it's updated to use the return value of pwq_activate_first_inactive() to tell whether a work item has been activated.
- nr_active decrement and activating the first inactive work item is factored into pwq_dec_nr_active().
v3: - WARN_ON_ONCE(!WORK_STRUCT_INACTIVE) added to __pwq_activate_work() as now we're calling the function unconditionally from pwq_activate_first_inactive().
v2: - wq->max_active now uses WRITE/READ_ONCE() as suggested by Lai.
Signed-off-by: Tejun Heo tj@kernel.org Reviewed-by: Lai Jiangshan jiangshanlai@gmail.com Stable-dep-of: 5797b1c18919 ("workqueue: Implement system-wide nr_active enforcement for unbound workqueues") Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/workqueue.c | 86 ++++++++++++++++++++++++++++++++++++---------- 1 file changed, 67 insertions(+), 19 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 861d8c7d6449a..78b4f4e3e41dd 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1458,11 +1458,14 @@ static bool pwq_is_empty(struct pool_workqueue *pwq) static void __pwq_activate_work(struct pool_workqueue *pwq, struct work_struct *work) { + unsigned long *wdb = work_data_bits(work); + + WARN_ON_ONCE(!(*wdb & WORK_STRUCT_INACTIVE)); trace_workqueue_activate_work(work); if (list_empty(&pwq->pool->worklist)) pwq->pool->watchdog_ts = jiffies; move_linked_works(work, &pwq->pool->worklist, NULL); - __clear_bit(WORK_STRUCT_INACTIVE_BIT, work_data_bits(work)); + __clear_bit(WORK_STRUCT_INACTIVE_BIT, wdb); }
/** @@ -1487,12 +1490,66 @@ static bool pwq_activate_work(struct pool_workqueue *pwq, return true; }
-static void pwq_activate_first_inactive(struct pool_workqueue *pwq) +/** + * pwq_tryinc_nr_active - Try to increment nr_active for a pwq + * @pwq: pool_workqueue of interest + * + * Try to increment nr_active for @pwq. Returns %true if an nr_active count is + * successfully obtained. %false otherwise. + */ +static bool pwq_tryinc_nr_active(struct pool_workqueue *pwq) +{ + struct workqueue_struct *wq = pwq->wq; + struct worker_pool *pool = pwq->pool; + bool obtained; + + lockdep_assert_held(&pool->lock); + + obtained = pwq->nr_active < READ_ONCE(wq->max_active); + + if (obtained) + pwq->nr_active++; + return obtained; +} + +/** + * pwq_activate_first_inactive - Activate the first inactive work item on a pwq + * @pwq: pool_workqueue of interest + * + * Activate the first inactive work item of @pwq if available and allowed by + * max_active limit. + * + * Returns %true if an inactive work item has been activated. %false if no + * inactive work item is found or max_active limit is reached. + */ +static bool pwq_activate_first_inactive(struct pool_workqueue *pwq) +{ + struct work_struct *work = + list_first_entry_or_null(&pwq->inactive_works, + struct work_struct, entry); + + if (work && pwq_tryinc_nr_active(pwq)) { + __pwq_activate_work(pwq, work); + return true; + } else { + return false; + } +} + +/** + * pwq_dec_nr_active - Retire an active count + * @pwq: pool_workqueue of interest + * + * Decrement @pwq's nr_active and try to activate the first inactive work item. + */ +static void pwq_dec_nr_active(struct pool_workqueue *pwq) { - struct work_struct *work = list_first_entry(&pwq->inactive_works, - struct work_struct, entry); + struct worker_pool *pool = pwq->pool;
- pwq_activate_work(pwq, work); + lockdep_assert_held(&pool->lock); + + pwq->nr_active--; + pwq_activate_first_inactive(pwq); }
/** @@ -1510,14 +1567,8 @@ static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, unsigned long work_ { int color = get_work_color(work_data);
- if (!(work_data & WORK_STRUCT_INACTIVE)) { - pwq->nr_active--; - if (!list_empty(&pwq->inactive_works)) { - /* one down, submit an inactive one */ - if (pwq->nr_active < READ_ONCE(pwq->wq->max_active)) - pwq_activate_first_inactive(pwq); - } - } + if (!(work_data & WORK_STRUCT_INACTIVE)) + pwq_dec_nr_active(pwq);
pwq->nr_in_flight[color]--;
@@ -1819,13 +1870,11 @@ static void __queue_work(int cpu, struct workqueue_struct *wq, * @work must also queue behind existing inactive work items to maintain * ordering when max_active changes. See wq_adjust_max_active(). */ - if (list_empty(&pwq->inactive_works) && - pwq->nr_active < READ_ONCE(pwq->wq->max_active)) { + if (list_empty(&pwq->inactive_works) && pwq_tryinc_nr_active(pwq)) { if (list_empty(&pool->worklist)) pool->watchdog_ts = jiffies;
trace_workqueue_activate_work(work); - pwq->nr_active++; insert_work(pwq, work, &pool->worklist, work_flags); kick_pool(pool); } else { @@ -4687,9 +4736,8 @@ static void wq_adjust_max_active(struct workqueue_struct *wq) /* this function can be called during early boot w/ irq disabled */ raw_spin_lock_irqsave(&pwq->pool->lock, flags);
- while (!list_empty(&pwq->inactive_works) && - pwq->nr_active < wq->max_active) - pwq_activate_first_inactive(pwq); + while (pwq_activate_first_inactive(pwq)) + ;
kick_pool(pwq->pool);