Re: + delay-accounting-taskstats-interface-send-tgid-once.patch added to -mm tree

[Arjan van de Ven <arjan@infradead.org>]

> CPU 0                		CPU 1
> (in irq)            	 	(in the code above)

actually CPU 0 doesn't even have to be in irq context; any context will
do

> 		     		stats_lock is taken
> tasklist_lock is taken	     	
> stats_lock_is taken <spin>	
> 				<interrupt happens>
> 		     		tasklist_lock is taken
> 		     
> which now forms an AB-BA deadlock!
> 
> 
> this happens at least in copy_process which can call taskstats_tgid_free
> without first disabling interrupts (via cleanup_signal). There may be
> many other cases, I've not checked deeper yet.
> 
> Solution should be to make these functions use irqsave variant... any
> comments from the authors of this patch ?
> 
> 
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