netdev - Re: [Bugme-new] [Bug 10737] New: pktgen procfs problem

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Date:	Tue, 20 May 2008 00:45:43 +0200
From:	Robert Olsson <Robert.Olsson@...a.slu.se>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	bugme-daemon@...zilla.kernel.org, devzero@....de, akpm@...l.org,
	kaber@...sh.net, den@...nvz.org, adobriyan@...allels.com,
	netdev@...r.kernel.org
Subject: Re: [Bugme-new] [Bug 10737] New: pktgen procfs problem


Alexey Dobriyan writes:
 > > list_del corruption. prev->next should be ffff81007e8a5e70, but was 6b6b6b6b6b6b6b6b
 > > kernel BUG at lib/list_debug.c:67!
 > >	:pktgen:pktgen_thread_worker+0x374/0x10b0
 > >	? autoremove_wake_function+0x0/0x40
 > >	? _spin_unlock_irqrestore+0x42/0x80
 > >	? :pktgen:pktgen_thread_worker+0x0/0x10b0
 > >	kthread+0x4d/0x80
 > >	child_rip+0xa/0x12
 > >	? restore_args+0x0/0x30
 > >	? kthread+0x0/0x80
 > >	? child_rip+0x0/0x12
 > > RIP  list_del+0x48/0x70
 > 
 > OK, trivial debugging and we know that worker thread function
 > (pktgen_thread_worker) never ran between kthread creation and rmmod.
 > 
 > Consequently, addition to "pktgen_threads" list happened, list_del of
 > thread 0 never happened, list_del of thread 1 barfs.

 Yes a schedule_timeout_interruptible(1) first in pg_cleanup seems to "cure" 
 insmod/rmmod race. You can even put the delay between the two proc removal 
 calls. But it seems we need a better way to sync so both start and stop 
 happen for all threads in pktgen_thread_worker before we remove the last proc 
 entries. And I see this with just one "controlling" process. 

 Cheers.
					--ro
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