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

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Date:	Wed, 22 Oct 2008 12:49:54 +0400
From:	Andrey Mirkin <major@...nvz.org>
To:	devel@...nvz.org, Pavel Emelyanov <xemul@...nvz.org>
Cc:	Cedric Le Goater <clg@...ibm.com>,
	containers@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [Devel] Re: [PATCH 08/10] Introduce functions to restart a process

On Monday 20 October 2008 13:23 Cedric Le Goater wrote:
> Hello Andrey !
>
> > diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
> > index 109792b..a4848a3 100644
> > --- a/arch/x86/kernel/entry_32.S
> > +++ b/arch/x86/kernel/entry_32.S
> > @@ -225,6 +225,7 @@ ENTRY(ret_from_fork)
> >  	GET_THREAD_INFO(%ebp)
> >  	popl %eax
> >  	CFI_ADJUST_CFA_OFFSET -4
> > +ret_from_fork_tail:
> >  	pushl $0x0202			# Reset kernel eflags
> >  	CFI_ADJUST_CFA_OFFSET 4
> >  	popfl
> > @@ -233,6 +234,26 @@ ENTRY(ret_from_fork)
> >  	CFI_ENDPROC
> >  END(ret_from_fork)
> >
> > +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.

Andrey
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