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Date: Thu, 2 Jun 2011 18:36:54 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Tejun Heo <tj@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>,
        indan@nul.nu, bdonlan@gmail.com, linux-kernel@vger.kernel.org,
        jan.kratochvil@redhat.com, akpm@linux-foundation.org
Subject: Re: thread leader death under strace (was Re: [PATCH 03/10]
	ptrace: implement PTRACE_SEIZE)
Message-ID: <20110602163654.GA17754@redhat.com>
References: <BANLkTin1q-r=b3ZVbT3vdJ59OEddrRWfsQ@mail.gmail.com>
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On 06/02, Denys Vlasenko wrote:
>
> The problem is that right now it seems that if tracer doesn't catch
> EVENT_EXIT and detach tracee when it sees it, really weird things
> happen.

The test-case is wrong afaics...

Perhaps this should be considered as a bug in glibc, I dunno.

> thread1(void *unused)
> {
> //	usleep(100*1000);
> //	VERBOSE("WINCH\n");
> //	raise(SIGWINCH);
>
> 	usleep(100*1000);
> 	VERBOSE("DYING\n");
> 	raise(SIGUSR1);

This doesn't send a signal. This does tgkill(tgid, 0, SIGUSR1) which
fails correctly with -EINVAL.

> static int
> thread_leader(void *unused)
> {
> 	/* malloc gives sufficiently aligned buffer.
> 	 * long buf[] does not! (on ia64).
> 	 */
> 	clone2(thread1, malloc(16 * 1024), 16 * 1024, 0

Probably because of this clone2.

Could you test with pthread_create? Or s/raise/tkill/ ?

Oleg.