Date: Tue, 24 Sep 2013 22:29:09 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Jilles Tjoelker <jilles@stack.nl> Cc: Tijl Coosemans <tijl@coosemans.org>, Russ Cox <rsc@swtch.com>, freebsd-current@FreeBSD.org Subject: Re: restarting SYSCALL system call on amd64 loses arguments Message-ID: <20130924192909.GO41229@kib.kiev.ua> In-Reply-To: <20130924191949.GA12607@stack.nl> References: <20130923222613.548860a3@kalimero.tijl.coosemans.org> <20130923213730.GX41229@kib.kiev.ua> <20130924191949.GA12607@stack.nl>
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--1Fyuj5/hnKieOVoO Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Sep 24, 2013 at 09:19:49PM +0200, Jilles Tjoelker wrote: > On Tue, Sep 24, 2013 at 12:37:30AM +0300, Konstantin Belousov wrote: > > On Mon, Sep 23, 2013 at 10:26:13PM +0200, Tijl Coosemans wrote: > > > Has anyone taken a look at this PR yet? >=20 > > > http://www.freebsd.org/cgi/query-pr.cgi?pr=3D182161 >=20 > > This looks like a valid bug, but probably not a valid testcase. >=20 > > Let me elaborate. When a signal is delivered, return from the signal > > handler is performed by the sigreturn(2), which reloads the whole > > register file when crossing kernel->user boundary due to sys_sigreturn(= 9) > > setting PCB_FULL_IRET flag. As result, the whole trap frame at the > > time of the syscall entry is restored, and ERESTART return is not > > exercised. >=20 > > I was not able to reproduce the issue with the supplied test program > > on HEAD. I suspect that the program actually exposed the bug in the > > signal delivery in the threaded processes, which I introduced for 9.1 > > and fixed in r251047 & r251365. >=20 > The ERESTART return happens if there is no signal or no longer a signal. > The latter is how the bug in the PR occurs: a SIGCHLD delivery via > handler in one thread races with a SIGCHLD acceptance in wait4() in > another thread. Note wait4() returning a value in the other thread in > the fourth line of the kdump output in the PR. >=20 > For some reason, I can reproduce this easily on my local quad-core > r255729 stable/9 system but not on ref9-amd64.freebsd.org or > ref10-amd64.freebsd.org. >=20 > I can also reproduce the bug on my local system by racing signal > delivery via handler with acceptance in sigtimedwait(). So, could you, please, check the r255844 on your machine ? --1Fyuj5/hnKieOVoO Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.21 (FreeBSD) iQIcBAEBAgAGBQJSQegFAAoJEJDCuSvBvK1BTtYP/R3Q7xLegWQZUco+26L1XZ1I mQca1BHv4HByPwSVqhCdOYQ1MMCfy3//is+28ZSdjZKzmIb/Pr+xWSrRMWE4JltY hM2pUwWg703hTb+tXCo9y4hXKgUNj3KxfEAb1hkdB8bzuoxWOPrrmnIH0jEFwytI b3KkMa9qFuuXZDkS/zVRf5a/tz0XM3TEfqtgNSRMczZ8Qou49TLqq3FMKKd3vEV4 yYV0O6ktsG9h0r0GH1ZI+Iwbn/2mQoESg9o/wTpStRJbrPGaoakirtPQqwwRiy76 ANXH+neg2H1U3lPodLEkHfDTJTz15xbsa2bmM6JJaefSVo/i3CnSrpfzJyV0nKHS UZHy+jeVGOvMFh99ewX0yD1Ru1wCr45AaZfhe2DUEQ7riSDEKciHJwjTQdyFDeW4 F7sU/LK93kvYZBYMYCuUq7rieRUmEJVKd1by/0mpjxfl46GbsaP80veG8rEz4gOO /8meAZ1nYtEGdiDD7Z35A4cbawvoQ0lEnkuFpefvvVX0JcEwpRX8jcun6aVhjl3n CLMYIK+XOQXU+n46kXdKUv84Wn3lCndd0MCAywss6p/rSOhEaWfcRpha3gTmenpH P4h62Cfc/kucJkEnbMs8TQQk9KZZAJqZAxWvE1bJEXSc7Ef2Si7yFV+9zie29vWI oCC68eviuVx8iwDfXbY3 =Ssnb -----END PGP SIGNATURE----- --1Fyuj5/hnKieOVoO--
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