-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 01/15/2015 02:20 PM, Oleg Nesterov wrote: > math_state_restore() can race with kernel_fpu_begin() if irq comes > right after __thread_fpu_begin(), __save_init_fpu() will overwrite > fpu->state we are going to restore. > > Add 2 simple helpers, kernel_fpu_disable() and kernel_fpu_enable() > which simply set/clear in_kernel_fpu, and change > math_state_restore() to exclude kernel_fpu_begin() in between. > > Alternatively we could use local_irq_save/restore, but probably > these new helpers can have more users. > > Perhaps they should disable/enable preemption themselves, in this > case we can remove preempt_disable() in __restore_xstate_sig().
Given that math_state_restore does an implicit preempt_disable through local_irq_disable, I am not sure whether adding an explicit preempt_disable would be good or bad. It's not like the additional locking rule makes this code any more complex. > Signed-off-by: Oleg Nesterov <o...@redhat.com> Reviewed-by: Rik van Riel <r...@redhat.com> - -- All rights reversed -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQEcBAEBAgAGBQJUuHe8AAoJEM553pKExN6Ds4kH/2dIkmOlhUNF7npjpvRNy6As a7/QVBJOvo2IOD5My4An2f/pdfNiJyC4dwIN8tM3JngA2LM57VFR5TzaODByq9TI xxPKCm+SY6M3apCBx7CWyTEloEXYLjvxnVvNkbfkOhArrqJzJLGqDiV5nkMi13fs 96ibGr04vIYRJ6VJNOfmCq1psAO31Yy6ZKfAADbkiOn7VmZ/qZykyjylfeidNiyj PTSAx9htvb39N2EMjYRnqhypZ90LMCffYg7YMT4Wdc9+BorMz3oiwzZZSjI/WcBS Dr2rH80KNMQvSg2iYAtuWZB7BY4cnvhRqoFHqJsFQNzgVAksC0LYE+66bvQO0JQ= =nxZE -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
