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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Oleg Nesterov' <oleg@redhat.com>
CC:     'Linus Torvalds' <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Deepa Dinamani <deepa.kernel@gmail.com>,
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        Davidlohr Bueso <dave@stgolabs.net>,
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Subject: RE: [PATCH -mm 0/1] signal: simplify
 set_user_sigmask/restore_user_sigmask
Thread-Topic: [PATCH -mm 0/1] signal: simplify
 set_user_sigmask/restore_user_sigmask
Thread-Index: AQHVG8OiWeMKMn2zNEeA0y96arbBsKaOUFtAgAAW0gCAABcWoA==
Date:   Thu, 6 Jun 2019 11:29:49 +0000
Message-ID: <6e3eeb101a30431eb111ad739ab5d2b0@AcuMS.aculab.com>
References: <20190522032144.10995-1-deepa.kernel@gmail.com>
 <20190529161157.GA27659@redhat.com> <20190604134117.GA29963@redhat.com>
 <20190605155801.GA25165@redhat.com>
 <CAHk-=wjkNx8u4Mcm5dfSQKYQmLQAv1Z1yGLDZvty7BVSj4eqBA@mail.gmail.com>
 <1285a2e60e3748d8825b9b0e3500cd28@AcuMS.aculab.com>
 <20190606110522.GA4691@redhat.com>
In-Reply-To: <20190606110522.GA4691@redhat.com>
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From: Oleg Nesterov
> Sent: 06 June 2019 12:05
> On 06/06, David Laight wrote:
> >
> > If a signal handler is called, I presume that the trampoline
> > calls back into the kernel to get further handlers called
> > and to finally restore the original signal mask?
> 
> See sigmask_to_save(), this is what the kernel records in uc.uc_sigmask
> before the signal handler runs, after that current->saved_sigmask has no
> meaning.

Some of this code is hard to grep through :-)

> When signal handler returns it does sys_rt_sigreturn() which restores
> the original mask saved in uc_sigmask.

Does that mean that if 2 signals interrupt epoll_wait() only
one of the signal handlers is run?

	David

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