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. Thanks. -- Coly Li
