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

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Message-ID: <20110603152937.GB23757@redhat.com>
Date:	Fri, 3 Jun 2011 17:29:37 +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 06/03, Denys Vlasenko wrote:
>
> On Thursday 02 June 2011 18:39, Oleg Nesterov wrote:
> > > > 	raise(SIGUSR1);
> > >
> > > This doesn't send a signal. This does tgkill(tgid, 0, SIGUSR1) which
> > > fails correctly with -EINVAL.
>
> Yes. After I fixed this, it works as expected. See attached.
> The output is:

Great.

> > > > 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.
>
> This seems to be not a problem (it is defined to clone()).

Doesn't matter.

Unlike pthread_create() which uses CLONE_SETTLS, this doesn't setup
the tls area, and I assume you used -lpthread. In this case it is clear
why raise() doesn't work, pt-raise.c thinks that THREAD_GETMEM(tid)
should always work.

Oleg.

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