[PATCH] rtc: Avoid flush_scheduled_work() usage

* [PATCH] rtc: Avoid flush_scheduled_work() usage
@ 2022-04-19 14:27 Tetsuo Handa
  2022-04-30 10:25 ` [PATCH v2] " Tetsuo Handa
  0 siblings, 1 reply; 7+ messages in thread
From: Tetsuo Handa @ 2022-04-19 14:27 UTC (permalink / raw)
  To: Alessandro Zummo, Alexandre Belloni; +Cc: linux-rtc

Flushing system-wide workqueues is dangerous and will be forbidden.
Replace system_wq with local rtc_wq.

Link: https://lkml.kernel.org/r/49925af7-78a8-a3dd-bce6-cfc02e1a9236@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
This patch blindly converts schedule_work() into queue_work() within
drivers/rtc/dev.c, based on an assumption that none of work items
outside of drivers/rtc/dev.c needs to be handled by rtc_wq.
Did I convert correctly? Or, do you want to share this rtc_wq with
drivers/rtc/{interface,rtc-88pm860x,rtc-ds1305,rtc-ds1374.c,rtc-imxdi}.c ?

 drivers/rtc/dev.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/rtc/dev.c b/drivers/rtc/dev.c
index 69325aeede1a..a4a63fc5165f 100644
--- a/drivers/rtc/dev.c
+++ b/drivers/rtc/dev.c
@@ -17,6 +17,7 @@
 #include "rtc-core.h"
 
 static dev_t rtc_devt;
+static struct workqueue_struct *rtc_wq;
 
 #define RTC_DEV_MAX 16 /* 16 RTCs should be enough for everyone... */
 
@@ -62,7 +63,7 @@ static void rtc_uie_task(struct work_struct *work)
 		rtc->uie_timer_active = 1;
 		rtc->uie_task_active = 0;
 		add_timer(&rtc->uie_timer);
-	} else if (schedule_work(&rtc->uie_task) == 0) {
+	} else if (queue_work(rtc_wq, &rtc->uie_task) == 0) {
 		rtc->uie_task_active = 0;
 	}
 	spin_unlock_irq(&rtc->irq_lock);
@@ -78,7 +79,7 @@ static void rtc_uie_timer(struct timer_list *t)
 	spin_lock_irqsave(&rtc->irq_lock, flags);
 	rtc->uie_timer_active = 0;
 	rtc->uie_task_active = 1;
-	if ((schedule_work(&rtc->uie_task) == 0))
+	if (queue_work(rtc_eq, &rtc->uie_task) == 0)
 		rtc->uie_task_active = 0;
 	spin_unlock_irqrestore(&rtc->irq_lock, flags);
 }
@@ -119,7 +120,7 @@ static int set_uie(struct rtc_device *rtc)
 		rtc->stop_uie_polling = 0;
 		rtc->oldsecs = tm.tm_sec;
 		rtc->uie_task_active = 1;
-		if (schedule_work(&rtc->uie_task) == 0)
+		if (queue_work(rtc_wq, &rtc->uie_task) == 0)
 			rtc->uie_task_active = 0;
 	}
 	rtc->irq_data = 0;
@@ -562,6 +563,9 @@ void __init rtc_dev_init(void)
 {
 	int err;
 
+	rtc_wq = alloc_workqueue("rtc_wq", 0, 0);
+	BUG_ON(!rtc_wq);
+
 	err = alloc_chrdev_region(&rtc_devt, 0, RTC_DEV_MAX, "rtc");
 	if (err < 0)
 		pr_err("failed to allocate char dev region\n");
@@ -571,4 +575,5 @@ void __exit rtc_dev_exit(void)
 {
 	if (rtc_devt)
 		unregister_chrdev_region(rtc_devt, RTC_DEV_MAX);
+	destroy_workqueue(rtc_wq);
 }
-- 
2.32.0

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