On 2020/3/3 4:33 上午, Jens Axboe wrote: > On 3/2/20 10:32 AM, Coly Li wrote: >> On 2020/3/3 1:19 上午, Jens Axboe wrote: >>> On 3/2/20 10:16 AM, Coly Li wrote: >>>> On 2020/3/2 9:49 下午, Oleg Nesterov wrote: >>>>> On 03/02, Michal Hocko wrote: >>>>>> >>>>>> I cannot really comment on the bcache part because I am not familiar >>>>>> with the code. >>>>> >>>>> same here... >>>>> >>>>>>> This patch calls flush_signals() in bcache_device_init() if there is >>>>>>> pending signal for current process. It avoids bcache registration >>>>>>> failure in system boot up time due to bcache udev rule timeout. >>>>>> >>>>>> this sounds like a wrong way to address the issue. Killing the udev >>>>>> worker is a userspace policy and the kernel shouldn't simply ignore it. >>>>> >>>>> Agreed. If nothing else, if a userspace process has pending SIKILL then >>>>> flush_signals() is very wrong. >>>>> >>>>>> Btw. Oleg, I have noticed quite a lot of flush_signals usage in the >>>>>> drivers land and I have really hard time to understand their purpose. >>>>> >>>>> Heh. I bet most if not all users of flush_signals() are simply wrong. >>>>> >>>>>> What is the actual valid usage of this function? >>>>> >>>>> I thinks it should die... It was used by kthreads, but today >>>>> signal_pending() == T is only possible if kthread does allow_signal(), >>>>> and in this case it should probably use kernel_dequeue_signal(). >>>>> >>>>> >>>>> Say, io_sq_thread(). Why does it do >>>>> >>>>> if (signal_pending(current)) >>>>> flush_signals(current); >>>>> >>>>> afaics this kthread doesn't use allow_signal/allow_kernel_signal, this >>>>> means that signal_pending() must be impossible even if this kthread sleeps >>>>> in TASK_INTERRUPTIBLE state. Add Jens. >>>> >>>> Hi Oleg, >>>> >>>> Can I use disallow_signal() before the registration begins and use >>>> allow_signal() after the registration done. Is this a proper way to >>>> ignore the signal sent by udevd for timeout ? >>>> >>>> For me the above method seems to solve my problem too. >>> >>> Really seems to me like you're going about this all wrong. The issue is >>> that systemd is killing the startup, because it's taking too long. Don't >>> try and work around that, ensure the timeout is appropriate. >>> >> >> Copied. Then let me try how to make event_timeout works on my udevd. If >> it works without other side effect, I will revert existing >> flush_signals() patches. > > Thanks, this one, right? > > commit 0b96da639a4874311e9b5156405f69ef9fc3bef8 > Author: Coly Li <colyli@xxxxxxx> > Date: Thu Feb 13 22:12:05 2020 +0800 > > bcache: ignore pending signals when creating gc and allocator thread > > because that definitely needs to be reverted. > Yes, please revert this commit. Thank you. -- Coly Li
