linux-kernel - Re: [PATCH 0/18] change mmap_sem taken for write killable

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Message-ID: <20160229141622.GC16930@dhcp22.suse.cz>
Date:	Mon, 29 Feb 2016 15:16:22 +0100
From:	Michal Hocko <mhocko@...nel.org>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Alex Deucher <alexander.deucher@....com>,
	Alex Thorlton <athorlton@....com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Christian König <christian.koenig@....com>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	David Airlie <airlied@...ux.ie>,
	Davidlohr Bueso <dave@...olabs.net>,
	David Rientjes <rientjes@...gle.com>,
	"H . Peter Anvin" <hpa@...or.com>, Hugh Dickins <hughd@...gle.com>,
	Ingo Molnar <mingo@...nel.org>,
	Johannes Weiner <hannes@...xchg.org>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	linux-arch@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Petr Cermak <petrcermak@...omium.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 0/18] change mmap_sem taken for write killable

On Mon 29-02-16 17:04:16, Kirill A. Shutemov wrote:
[...]
> > Most of the patches are really trivial because the lock is help from a
> > shallow syscall paths where we can return EINTR trivially. Others seem
> > to be easy as well as the callers are already handling fatal errors and
> > bail and return to userspace which should be sufficient to handle the
> > failure gracefully. I am not familiar with all those code paths so a
> > deeper review is really appreciated.
> 
> What about effect on userspace? IIUC, we would have now EINTR returned
> from bunch of syscall, which haven't had this errno on the table before.
> Should we care?

Those function will return EINTR only when the current was _killed_ when
we do not return to the userspace. So there shouldn't be any visible
effect.
-- 
Michal Hocko
SUSE Labs