Messages in this thread | | | Date | Wed, 22 Oct 2008 11:25:03 -0400 | From | Oren Laadan <> | Subject | Re: [Devel] Re: [PATCH 08/10] Introduce functions to restart a process |
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Andrey Mirkin wrote: > On Wednesday 22 October 2008 13:25 Louis Rilling wrote: >> On Wed, Oct 22, 2008 at 12:49:54PM +0400, Andrey Mirkin wrote: >>> 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. >> Do you checkpoint uninterruptible syscalls as well? If only interruptible >> syscalls are checkpointed, I'd say that either this syscall uses >> ERESTARTSYS or ERESTART_RESTARTBLOCK, and then signal handling code already >> does the trick, or this syscall does not restart itself when interrupted, >> and well, this is life, userspace just sees -EINTR, which is allowed by the >> syscall spec. >> Actually this is how we checkpoint/migrate tasks in interruptible syscalls >> in Kerrighed and this works. > > We checkpoint only interruptible syscalls. Some syscalls do not restart > themself, that is why after restarting a process we restart syscall to > complete it.
Can you please elaborate on this ? I don't recall having had issues with that.
Thanks,
Oren.
> > Andrey > _______________________________________________ > Containers mailing list > Containers@lists.linux-foundation.org > https://lists.linux-foundation.org/mailman/listinfo/containers
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