Re: [syzbot] [input?] possible deadlock in tasklet_action_common (2)

[Hillf Danton <hdanton@sina.com>]

> Date: Sat, 25 Jul 2026 17:38:28 -0700	[thread overview]
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    cc2b5f627e8c Add linux-next specific files for 20260714
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=13d446b9580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2290ccbf984c524f
> dashboard link: https://syzkaller.appspot.com/bug?extid=b5d7ab56d43de3fd5aac
> compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1310a232580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13c3b2ea580000

#syz test

--- x/kernel/softirq.c
+++ y/kernel/softirq.c
@@ -924,7 +924,6 @@ static void tasklet_action_common(struct
 	tl_head->tail = &tl_head->head;
 	local_irq_enable();
 
-	tasklet_lock_callback();
 	while (list) {
 		struct tasklet_struct *t = list;
 
@@ -944,7 +943,6 @@ static void tasklet_action_common(struct
 					}
 				}
 				tasklet_unlock(t);
-				tasklet_callback_sync_wait_running();
 				continue;
 			}
 			tasklet_unlock(t);
@@ -957,7 +955,6 @@ static void tasklet_action_common(struct
 		__raise_softirq_irqoff(softirq_nr);
 		local_irq_enable();
 	}
-	tasklet_unlock_callback();
 }
 
 static __latent_entropy void tasklet_action(void)
@@ -1006,11 +1003,10 @@ void tasklet_unlock_spin_wait(struct tas
 	while (test_bit(TASKLET_STATE_RUN, &(t)->state)) {
 		if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
 			/*
-			 * Prevent a live lock when current preempted soft
-			 * interrupt processing or prevents ksoftirqd from
-			 * running.
+			 * wait_on_bit(TASKLET_STATE_RUN)
+			 * https://lore.kernel.org/lkml/20260524004526.1046-1-hdanton@sina.com/
 			 */
-			tasklet_callback_cancel_wait_running();
+			tasklet_unlock_wait(t);
 		} else {
 			cpu_relax();
 		}
--