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From: Roland McGrath <roland@redhat.com>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Badari Pulavarty <pbadari@us.ibm.com>,
	Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@osdl.org>,
	lkml <linux-kernel@vger.kernel.org>
Subject: Re: 2.6.14-rc1 wait()/SIG_CHILD bevahiour
Date: Mon, 19 Sep 2005 16:34:40 -0700 (PDT)	[thread overview]
Message-ID: <20050919233440.AC5D8180E1D@magilla.sf.frob.com> (raw)
In-Reply-To: Linus Torvalds's message of  Monday, 19 September 2005 12:14:54 -0700 <Pine.LNX.4.58.0509191206040.2553@g5.osdl.org>

The test program is buggy.  Here is one clue:

	elm3b29:~ # strace -p 30023
	Process 30023 attached - interrupt to quit
	futex(0x2aaaaaddf118, FUTEX_WAIT, 2, NULL

It's not anywhere near wait4.  It's deadlocked in the rand() call inside
rand_delay, called from sigchld_handler.  You cannot safely call rand
inside a signal handler, for exactly this reason.  The signal came during
another rand call and attempted to reenter.  If this sort of deadlock is
the failure mode of your real-world case, then it is probably an
application bug.  If this deadlock is just a mistake in your test program
here, then you'll need to give us a corrected test program to pursue
whatever real kernel issue you may have.


Thanks,
Roland

  reply	other threads:[~2005-09-19 23:34 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-09-19 17:39 Badari Pulavarty
2005-09-19 18:01 ` Kyle Moffett
2005-09-19 18:19   ` Badari Pulavarty
2005-09-19 19:14 ` Linus Torvalds
2005-09-19 23:34   ` Roland McGrath [this message]
2005-09-20 16:49     ` Badari Pulavarty
2005-09-19 20:53 ` Edgar Toernig

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