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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@amacapital.net>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar 2015-05-27 12:22:29 +02:00
parent 0560281266
commit 9ba6b79102
1 changed files with 1 additions and 4 deletions
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5
arch/x86/kernel/fpu/core.c
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@ -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: */