linux-kernel - Re: [Devel] Re: [PATCH 08/10] Introduce functions to restart a process

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Date:	Wed, 22 Oct 2008 14:47:50 +0200
From:	Cedric Le Goater <clg@...ibm.com>
To:	Andrey Mirkin <major@...nvz.org>
CC:	devel@...nvz.org, Pavel Emelyanov <xemul@...nvz.org>,
	containers@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [Devel] Re: [PATCH 08/10] Introduce functions to restart a process

>>> +ENTRY(i386_ret_from_resume)
>>> +	CFI_STARTPROC
>>> +	pushl %eax
>>> +	CFI_ADJUST_CFA_OFFSET 4
>>> +	call schedule_tail
>>> +	GET_THREAD_INFO(%ebp)
>>> +	popl %eax
>>> +	CFI_ADJUST_CFA_OFFSET -4
>>> +	movl (%esp), %eax
>>> +	testl %eax, %eax
>>> +	jz    1f
>>> +	pushl %esp
>>> +	call  *%eax
>>> +	addl  $4, %esp
>>> +1:
>>> +	addl  $256, %esp
>>> +	jmp   ret_from_fork_tail
>>> +	CFI_ENDPROC
>>> +END(i386_ret_from_resume)
>> Could you explain why you need to do this
>>
>> 	call  *%eax
>>
>> is it related to the freezer code ?
> 
> It is not related to the freezer code actually.
> That is needed to restart syscalls. Right now I don't have a code in my 
> patchset which restarts a syscall, but later I plan to add it.
> In OpenVZ checkpointing we restart syscalls if process was caught in syscall 
> during checkpointing.

ok. I get it now. why 256 bytes of extra stack ? I'm sure it's not random. 

Thanks,

C.
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