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Date: Thu, 2 Jun 2011 14:03:40 +0900 From: Tejun Heo <tj@...nel.org> To: Oleg Nesterov <oleg@...hat.com> Cc: vda.linux@...glemail.com, jan.kratochvil@...hat.com, linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org, akpm@...ux-foundation.org, indan@....nu, bdonlan@...il.com, pedro@...esourcery.com Subject: Re: [PATCH 01/17] ptrace: remove silly wait_trap variable from ptrace_attach() Hello, On Wed, Jun 01, 2011 at 08:47:43PM +0200, Oleg Nesterov wrote: > On 05/30, Tejun Heo wrote: > > - if (wait_trap) > > - wait_event(current->signal->wait_chldexit, > > - !(task->group_stop & GROUP_STOP_TRAPPING)); > > + wait_event(current->signal->wait_chldexit, > > + !(task->group_stop & GROUP_STOP_TRAPPING)); > > return retval; > > Well, it doesn't change anything, but only if ptrace_attach() succeeds. > The caller should not wait if STOP_TRAPPING was already set by another > tracer and we are going to fail. Afaics, nothing really bad can happen > but still this doesn't look very clean. > > And. Please note that this patch is buggy until 8/17 "use bit_waitqueue > for TRAPPING", wait_event(current->signal->wait_chldexit) can hang forever > in this case since we are not ->parent. Ah, darn it. It was part of later patch which got dropped and I just salavaged this part and put it at the front forgetting about the chldexit conversion. > I agree, wait_trap should go away. We can hit STOP_TRAPPING after attach > if we change detach to set this bit. But perhaps it would be more clean > to not call wait_event/wait_bit unconditionally anyway, we can check > retval == 0. Yeap, that sounds about right. Will post updated patch. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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