linux-kernel - Re: Sending signals to a kernel thread, broken in 2.6.22

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Date:	Wed, 30 May 2007 15:22:34 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Sending signals to a kernel thread, broken in 2.6.22

Alan Stern wrote:
>
> The g_file_storage driver uses a kernel thread and communicates with
> that thread in part by means of signals.  It also relies on the thread
> receiving signals from userspace as an indication that the thread
> should terminate.
>
> This was all working in 2.6.21, but as of 2.6.22-rc3 the signal
> delivery mechanism (entirely within the kernel!) is no longer
> functional.
>
> What's the story?  Do I need to do something new and different to get
> signals working again?  Should I avoid using signals entirely?

I guess you mean drivers/usb/gadget/file_storage.c

	fsg_main_thread:
		
		siginitsetinv(&fsg->thread_signal_mask, SIGTERM | ...);
		sigprocmask(SIG_SETMASK, &fsg->thread_signal_mask, NULL);

Yes?

Please look at

	change kernel threads to ignore signals instead of blocking them
	commit: 10ab825bdef8df510f99c703a5a2d9b13a4e31a5

I think you can convert the code above to use allow_signal().


Please note that it is not good to just unblock the signal, SIG_DFL means
that __group_complete_signal() starts doing SIGNAL_GROUP_EXIT things. In
particular, SIGTERM implies sigaddset(SIGKILL).

Oleg.

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