Commit-ID: 9ba6b79102a594293c79f30319cabf476c5e300e
Gitweb: http://git.kernel.org/tip/9ba6b79102a594293c79f30319cabf476c5e300e
Author: Ingo Molnar <mingo@xxxxxxxxxx>
AuthorDate: Wed, 27 May 2015 12:22:29 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 27 May 2015 14:11:25 +0200
x86/fpu: Optimize fpu__activate_fpstate_read()
fpu__activate_fpstate_read() is used before FPU registers are
read from the fpstate by ptrace and core dumping.
It's not necessary to unlazy non-current child tasks in this case,
since the reading of registers is non-destructive.
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Bobby Powers <bobbypowers@xxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/kernel/fpu/core.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 174add3..06cb7e3 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -312,10 +312,7 @@ void fpu__activate_fpstate_read(struct fpu *fpu)
if (fpu->fpregs_active) {
fpu__save(fpu);
} else {
- if (fpu->fpstate_active) {
- /* Invalidate any lazy state: */
- fpu->last_cpu = -1;
- } else {
+ if (!fpu->fpstate_active) {
fpstate_init(&fpu->state);
/* Safe to do for current and for stopped child tasks: */
--
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