Re: [PATCH][2.5] flush_tlb_all is not preempt safe.

From: Zwane Mwaikambo (zwane@holomorphy.com)
Date: Sat Feb 15 2003 - 08:41:41 EST

On Fri, 14 Feb 2003, Zwane Mwaikambo wrote:

> On Fri, 14 Feb 2003, Zwane Mwaikambo wrote:
>
> > Hi,
> > Considering that smp_call_function isn't allowed to hold a lock
> > reference and within smp_call_function we lock and unlock call_lock thus
> > triggering a preempt point. Therefore we can't guarantee that we'll be on
> > the same processor when we hit do_flush_tlb_all_local.
> >
> > void flush_tlb_all(void)
> > {
> > preempt_disable();
> > smp_call_function (flush_tlb_all_ipi,0,1,1);
> >
> > do_flush_tlb_all_local();
> > preempt_enable();
> > }
>
> Of course i had to go and paste the code i was working on. The original
> isn't wrapped in preempt_disable/enable.
>
> Zwane (who really needs to get to bed now)

void flush_tlb_all(void)
{
        BUG_ON(preempt_count() == 0);
        smp_call_function (flush_tlb_all_ipi,0,1,1);

        do_flush_tlb_all_local();
}

------------[ cut here ]------------
kernel BUG at arch/i386/kernel/smp.c:455!
invalid operand: 0000
CPU: 0
EIP: 0060:[<c01166d8>] Not tainted
EFLAGS: 00000246
EIP is at flush_tlb_all+0x88/0xa0
eax: 00000000 ebx: c1552000 ecx: 00040000 edx: 00040000
esi: c1bf7ec4 edi: 00000001 ebp: c1553f6c esp: c1553f68
ds: 007b es: 007b ss: 0068
Process swapoff (pid: 1936, threadinfo=c1552000 task=c143ad40)
Stack: c2811000 c1553f84 c015427b c1bf7ec4 00000000 c2811000 c059a4e0 c1553f94
       c015430e c2811000 00000001 c1553fbc c0156b06 c2811000 c1552000 ffffffff
       c1ad0a34 c1bfb2e4 bfffff1a bfffff18 080493eb c1552000 c0109957 bfffff1a
Call Trace:
 [<c015427b>] __vunmap+0x2b/0xa0
 [<c015430e>] vfree+0x1e/0x30
 [<c0156b06>] sys_swapoff+0x3c6/0x4d0
 [<c0109957>] syscall_call+0x7/0xb

Code: 0f 0b c7 01 2b f8 43 c0 eb 80 8d b4 26 00 00 00 00 8d bc 27

        Zwane 

-- 
function.linuxpower.ca
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This archive was generated by hypermail 2b29 : Sat Feb 15 2003 - 22:01:02 EST