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

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Message-ID: <20110602163909.GA18025@redhat.com>
Date:	Thu, 2 Jun 2011 18:39:09 +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, Oleg Nesterov wrote:
>
> 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/ ?

Btw, did you use -lpthread?

Oleg.

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