Re: [PATCH 2/3] x86, xsave: remove thread_has_fpu() bug check in__sanitize_i387_state()

From: Oleg Nesterov
Date: Wed May 09 2012 - 16:31:56 EST

Hi Suresh,

I can't really comment this series, my understanding of this code
is too limited.

But could you explain this patch? I am just curious.

On 05/08, Suresh Siddha wrote:
> BUG_ON() in __sanitize_i387_state() is checking that the fpu state
> is not live any more. But for preempt kernels, task can be scheduled
> out and in at any place and the preload_fpu logic during context switch
> can make the fpu registers live again.

And? Do you see any particular scenario when this BUG_ON() is wrong?

Afaics, __sanitize_i387_state() should not be called if the task can
be scheduled in with ->fpu_counter != 0.

> Similarly during core dump, thread dumping the core can schedule out
> and in for page-allocations etc in non-preempt case.

Again, can't understand. The core-dumping thread does init_fpu()
before it calls sanitize_i387_state().


To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at