On Wed, Oct 22, 2008 at 02:12:12PM +0400, 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.
I guess you do that to avoid breaking application that are badly written and do not handle -EINTR correctly with interruptible syscalls. Right? Louis -- Dr Louis Rilling Kerlabs Skype: louis.rilling Batiment Germanium Phone: (+33|0) 6 80 89 08 23 80 avenue des Buttes de Coesmes http://www.kerlabs.com/ 35700 Rennes
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