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Message-ID: <CAHSMefheea9cebcSmZTGf6r9yO=kN=6mTKpxMCUyx-21tFBPkw@mail.gmail.com>
Date: Tue, 29 Sep 2020 12:02:47 -0700
From: Leonid Shamis <leonid.shamis@...il.com>
To: Rich Felker <dalias@...c.org>
Cc: musl@...ts.openwall.com
Subject: Re: Robust mutex returning ESRCH
It was priority-inheritance.
Is it worth adding a check for ESRCH and converting it to EOWNERDEAD? Or
should it stay UB?
On Tue, Sep 29, 2020 at 11:48 AM Rich Felker <dalias@...c.org> wrote:
> On Tue, Sep 29, 2020 at 09:31:12AM -0700, Leonid Shamis wrote:
> > We had a bug in our code where a dying process released shared memory
> > (munmap) prior to exit. The process held ownership of a robust mutex
> within
> > the shared memory, and because the address was unmapped, the robust_list
> > wasn't able to set the appropriate flags.
> >
> > The next attempt to lock the mutex, in another process, returned ESRCH.
> >
> > Should ESRCH be caughtand converted to either a recoverable EOWNERDEAD or
> > ENOTRECOVERABLE?
>
> Was it also priority-inheritance? Otherwise I don't see where ESRCH
> should have come from. Unmapping the mutex while you hold is should
> almost surely be treated as undefined (though I don't think the
> standard spells this out explicitly anywhere). It probably would be
> nice to avoid returning a bogus error code to the non-erroneous caller
> sharing the robust mutex with a program that has UB, but I don't think
> Linux admits any efficient general solution here.
>
> Rich
>
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