Am 25.03.21 um 13:04 schrieb Eric W. Biederman: > Stefan Metzmacher <metze@xxxxxxxxx> writes: > >> Am 25.03.21 um 12:24 schrieb Sasha Levin: >>> From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> >>> >>> [ Upstream commit 4db4b1a0d1779dc159f7b87feb97030ec0b12597 ] >>> >>> Just like we don't allow normal signals to IO threads, don't deliver a >>> STOP to a task that has PF_IO_WORKER set. The IO threads don't take >>> signals in general, and have no means of flushing out a stop either. >>> >>> Longer term, we may want to look into allowing stop of these threads, >>> as it relates to eg process freezing. For now, this prevents a spin >>> issue if a SIGSTOP is delivered to the parent task. >>> >>> Reported-by: Stefan Metzmacher <metze@xxxxxxxxx> >>> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> >>> Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx> >>> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> >>> --- >>> kernel/signal.c | 3 ++- >>> 1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/kernel/signal.c b/kernel/signal.c >>> index 55526b941011..00a3840f6037 100644 >>> --- a/kernel/signal.c >>> +++ b/kernel/signal.c >>> @@ -288,7 +288,8 @@ bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask) >>> JOBCTL_STOP_SIGMASK | JOBCTL_TRAPPING)); >>> BUG_ON((mask & JOBCTL_TRAPPING) && !(mask & JOBCTL_PENDING_MASK)); >>> >>> - if (unlikely(fatal_signal_pending(task) || (task->flags & PF_EXITING))) >>> + if (unlikely(fatal_signal_pending(task) || >>> + (task->flags & (PF_EXITING | PF_IO_WORKER)))) >>> return false; >>> >>> if (mask & JOBCTL_STOP_SIGMASK) >>> >> >> Again, why is this proposed for 5.11 and 5.10 already? > > Has the bit about the io worker kthreads been backported? > If so this isn't horrible. If not this is nonsense. I don't know, I hope not... But I just tested v5.12-rc4 and attaching to an application with iothreads with gdb is still not possible, it still loops forever trying to attach to the iothreads. And I tested 'kill -9 $pidofiothread', and it feezed the whole machine... So there's still work to do in order to get 5.12 stable. I'm short on time currently, but I hope to send more details soon. metze
