linux-kernel - Re: strace, accept(), ERESTARTSYS and EINTR

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Date:	Sat, 05 Jan 2008 19:35:09 +0000
From:	"Phil Endecott" <phil_wueww_endecott@...zphil.org>
To:	"Andreas Schwab" <schwab@...e.de>
Cc:	"Jiri Slaby" <jirislaby@...il.com>, <linux-kernel@...r.kernel.org>,
	"Frederik Deweerdt" <deweerdt@...e.fr>
Subject: Re: strace, accept(), ERESTARTSYS and EINTR

Andreas Schwab wrote:
> "Phil Endecott" <phil_wueww_endecott@...zphil.org> writes:
>> Andreas Schwab wrote:
>>> "Phil Endecott" <phil_wueww_endecott@...zphil.org> writes:
>>>> However, there's a lot of code and I know that there are bugs in it.  I
>>>> just want to focus on the kernel-related issue that the strace fragment
>>>> that I posted brings up:  even if my user code gets completely screwed up
>>>> (corrupts its stack, runs out of FDs/VM/threads etc), I don't think that I
>>>> should see in the strace output that accept() has returned
>>>> ERESTARTSYS.
>>>
>>> strace always sees the raw return value, before the signal handler is
>>> executed and before the check for syscall restart is done.
>>
>> Yes, but I should see the real final return value in another strace output
>> line before I see that thread doing something else.  Correct?
>
> No.  As far as strace is concerned the syscall has finished.  Since it
> isn't restarted, you won't see it again in the trace.

Sorry for being dense, but what is the implication of your comment 
"Since it isn't restarted" ?  Are you saying that the kernel isn't 
going to restart it and will have converted it to EINTR and returned 
that to user-space, and that this modified return value is not reported 
by strace?


Phil.




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