Commit-ID: 4b2e762e2e53c721458a83d547b222178bb72a34 Gitweb: http://git.kernel.org/tip/4b2e762e2e53c721458a83d547b222178bb72a34 Author: Oleg Nesterov <[email protected]> AuthorDate: Mon, 19 Jan 2015 19:51:51 +0100 Committer: Borislav Petkov <[email protected]> CommitDate: Mon, 23 Feb 2015 15:50:41 +0100
x86/fpu: Always allow FPU in interrupt if use_eager_fpu() The __thread_has_fpu() check in interrupted_kernel_fpu_idle() was needed to prevent the nested kernel_fpu_begin(). Now that we have in_kernel_fpu and !__thread_has_fpu() case in __kernel_fpu_begin() does not depend on use_eager_fpu() (except clts) we can remove it. __thread_has_fpu() can be false even if use_eager_fpu(), but this case does not differ from !use_eager_fpu() case except we should not worry about X86_CR0_TS, __kernel_fpu_begin()/end() will not touch this bit. Note: I think we can kill all irq_fpu_usable() checks except in_kernel_fpu, just we need to record the state of X86_CR0_TS in __kernel_fpu_begin() and conditionalize stts() in __kernel_fpu_end(), but this needs another patch. Signed-off-by: Oleg Nesterov <[email protected]> Reviewed-by: Rik van Riel <[email protected]> Acked-by: Andy Lutomirski <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Suresh Siddha <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Borislav Petkov <[email protected]> --- arch/x86/kernel/i387.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index ad3a2a2..8416b5f 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -41,8 +41,8 @@ void kernel_fpu_enable(void) * be set (so that the clts/stts pair does nothing that is * visible in the interrupted kernel thread). * - * Except for the eagerfpu case when we return 1 unless we've already - * been eager and saved the state in kernel_fpu_begin(). + * Except for the eagerfpu case when we return true; in the likely case + * the thread has FPU but we are not going to set/clear TS. */ static inline bool interrupted_kernel_fpu_idle(void) { @@ -50,7 +50,7 @@ static inline bool interrupted_kernel_fpu_idle(void) return false; if (use_eager_fpu()) - return __thread_has_fpu(current); + return true; return !__thread_has_fpu(current) && (read_cr0() & X86_CR0_TS); -- 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/
