linux-kernel - Re: thread leader death under strace (was Re: [PATCH 03/10] ptrace: implement PTRACE

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Message-ID: <20110602163654.GA17754@redhat.com>
Date:	Thu, 2 Jun 2011 18:36:54 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Denys Vlasenko <vda.linux@...glemail.com>
Cc:	Tejun Heo <tj@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>, indan@....nu,
	bdonlan@...il.com, linux-kernel@...r.kernel.org,
	jan.kratochvil@...hat.com, akpm@...ux-foundation.org
Subject: Re: thread leader death under strace (was Re: [PATCH 03/10]
	ptrace: implement PTRACE_SEIZE)

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.

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