On 07/07, Pavel Begunkov wrote: > > io_uring can asynchronously add a task_work while the task is getting > freezed. TIF_NOTIFY_SIGNAL will prevent the task from sleeping in > do_freezer_trap(), and since the get_signal()'s relock loop doesn't > retry task_work, the task will spin there not being able to sleep > until the freezing is cancelled / the task is killed / etc. > > Cc: stable@xxxxxxxxxxxxxxx > Link: https://github.com/systemd/systemd/issues/33626 > Fixes: 3146cba99aa28 ("io-wq: make worker creation resilient against signals") I don't think we should blame io_uring even if so far it is the only user of TWA_SIGNAL. Perhaps we should change do_freezer_trap() somehow, not sure... It assumes that TIF_SIGPENDING is the only reason to not sleep in TASK_INTERRUPTIBLE, today this is not true. > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -2694,6 +2694,10 @@ bool get_signal(struct ksignal *ksig) > try_to_freeze(); > > relock: > + clear_notify_signal(); > + if (unlikely(task_work_pending(current))) > + task_work_run(); > + > spin_lock_irq(&sighand->siglock); Well, but can't we kill the same code at the start of get_signal() then? Of course, in this case get_signal() should check signal_pending(), not task_sigpending(). Or perhaps something like the patch below makes more sense? I dunno... Oleg. diff --git a/kernel/signal.c b/kernel/signal.c index 1f9dd41c04be..e2ae85293fbb 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2676,6 +2676,7 @@ bool get_signal(struct ksignal *ksig) struct signal_struct *signal = current->signal; int signr; +start: clear_notify_signal(); if (unlikely(task_work_pending(current))) task_work_run(); @@ -2760,10 +2761,11 @@ bool get_signal(struct ksignal *ksig) if (current->jobctl & JOBCTL_TRAP_MASK) { do_jobctl_trap(); spin_unlock_irq(&sighand->siglock); + goto relock; } else if (current->jobctl & JOBCTL_TRAP_FREEZE) do_freezer_trap(); - - goto relock; + goto start; + } } /*
