Commit-ID: 7aeccb83e76316b365e4b44a1dd982ee22a7d8b2 Gitweb: http://git.kernel.org/tip/7aeccb83e76316b365e4b44a1dd982ee22a7d8b2 Author: Oleg Nesterov <[email protected]> AuthorDate: Mon, 19 Jan 2015 19:51:32 +0100 Committer: Borislav Petkov <[email protected]> CommitDate: Mon, 23 Feb 2015 15:50:28 +0100
x86/fpu: __kernel_fpu_begin() should clear fpu_owner_task even if use_eager_fpu() __kernel_fpu_begin() does nothing if !__thread_has_fpu() && use_eager_fpu(), perhaps it assumes that this case is simply impossible. This is certainly not possible if in_interrupt() == T; interrupted_user_mode() should have FPU, and interrupted_kernel_fpu_idle() should fail if !__thread_has_fpu(). However, even if use_eager_fpu() == T a task can do drop_fpu(), then switch to another thread which becomes fpu_owner_task, then resume and call some function which does kernel_fpu_begin(). Say, an exiting task does a lot of things after exit_thread(), it is not safe to assume that it can't use FPU in these paths. Signed-off-by: Oleg Nesterov <[email protected]> Reviewed-by: Rik van Riel <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Suresh Siddha <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Pekka Riikonen <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Borislav Petkov <[email protected]> --- arch/x86/kernel/i387.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index f59d806..ad3a2a2 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -93,9 +93,10 @@ void __kernel_fpu_begin(void) if (__thread_has_fpu(me)) { __save_init_fpu(me); - } else if (!use_eager_fpu()) { + } else { this_cpu_write(fpu_owner_task, NULL); - clts(); + if (!use_eager_fpu()) + clts(); } } EXPORT_SYMBOL(__kernel_fpu_begin); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
