Re: unusual scheduling performance

[Davide Libenzi]

On Mon, 18 Nov 2002, Dave Hansen wrote:

> As Andrew suggested, I put a dump_stack() in rwsem_down_write_failed().
>
> This was actually in a 2.5.47 bk snapshot, so it has eventpoll in it.
> kksymoops is broken, so:
> dmesg | tail -20 | sort | uniq | ksymoops -m /boot/System.map
>
> Trace; c01c5757 <rwsem_down_write_failed+27/170>
> Trace; c01220c6 <update_wall_time+16/50>
> Trace; c01223ee <do_timer+2e/c0>
> Trace; c0166bd3 <.text.lock.eventpoll+6/f3>
> Trace; c0146568 <__fput+18/c0>
> Trace; c010ae9a <handle_IRQ_event+2a/60>
> Trace; c0144a05 <filp_close+85/b0>
> Trace; c0144a8d <sys_close+5d/70>
> Trace; c0108fab <syscall_call+7/b>
>
> Trace; c01c5757 <rwsem_down_write_failed+27/170>
> Trace; c0166bd3 <.text.lock.eventpoll+6/f3>
> Trace; c0146568 <__fput+18/c0>
> Trace; c011e90b <do_softirq+6b/d0>
> Trace; c0144a05 <filp_close+85/b0>
> Trace; c0144a8d <sys_close+5d/70>
> Trace; c0108fab <syscall_call+7/b>
>
> Trace; c01c5757 <rwsem_down_write_failed+27/170>
> Trace; c0166bd3 <.text.lock.eventpoll+6/f3>
> Trace; c0146568 <__fput+18/c0>
> Trace; c0144c2d <generic_file_llseek+2d/e0>
> Trace; c0144a05 <filp_close+85/b0>
> Trace; c0144a8d <sys_close+5d/70>
> Trace; c0108fab <syscall_call+7/b>
>
> Trace; c01c5757 <rwsem_down_write_failed+27/170>
> Trace; c0166bd3 <.text.lock.eventpoll+6/f3>
> Trace; c0146568 <__fput+18/c0>
> Trace; c01553fa <sys_getdents64+4a/98>
> Trace; c0144a05 <filp_close+85/b0>
> Trace; c0144a8d <sys_close+5d/70>
> Trace; c0108fab <syscall_call+7/b>
>
> Mystery solved?

Could you pls put this in eventpoll_release() :

        if (list_empty(lsthead))
                return;

	printk("[%p] head=%p prev=%p next=%p\n", current, lsthead,
		lsthead->prev, lsthead->next);

- Davide