Re: VM Problems in 2.6.7 (Too active OOM Killer)

[William Lee Irwin III]

On Wed, Jul 14, 2004 at 07:39:51PM -0700, William Lee Irwin III wrote:
> Careful not to make too much of ignoring signals, mm/oom_kill.c sets
> PF_MEMDIE out-of-context, so when an OOM kill is issued while a task
> is looping in __alloc_pages() it will eventually break out of the
> rebalance loop due to the flag.

However, note the modifications of task->flags are not atomic. In
principle, one may have:

__alloc_pages()			__oom_kill_task()
load current->flags		load current->flags
|= PF_MEMALLOC in registers	|= PF_MEMALLOC|PF_MEMDIE in registers
IRQ/delay/whatever		store current->flags
store current->flags		...
try_to_free_pages() etc.	force_sig() etc.

... and voila! PF_MEMDIE in ->flags has been lost.


-- wli
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