From a4d4fbc7735bba6654b20f859135f9d3f8fe7f76 Mon Sep 17 00:00:00 2001 From: Brian Gerst Date: Fri, 3 Sep 2010 21:17:12 -0400 Subject: [PATCH] x86-64, fpu: Disable preemption when using TS_USEDFPU Consolidates code and fixes the below race for 64-bit. commit 9fa2f37bfeb798728241cc4a19578ce6e4258f25 Author: torvalds Date: Tue Sep 2 07:37:25 2003 +0000 Be a lot more careful about TS_USEDFPU and preemption We had some races where we testecd (or set) TS_USEDFPU together with sequences that depended on the setting (like clearing or setting the TS flag in %cr0) and we could be preempted in between, which screws up the FPU state, since preemption will itself change USEDFPU and the TS flag. This makes it a lot more explicit: the "internal" low-level FPU functions ("__xxxx_fpu()") all require preemption to be disabled, and the exported "real" functions will make sure that is the case. One case - in __switch_to() - was switched to the non-preempt-safe internal version, since the scheduler itself has already disabled preemption. BKrev: 3f5448b5WRiQuyzAlbajs3qoQjSobw Signed-off-by: Brian Gerst Acked-by: Pekka Enberg Cc: Suresh Siddha LKML-Reference: <1283563039-3466-6-git-send-email-brgerst@gmail.com> Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/i387.h | 15 --------------- arch/x86/kernel/process_64.c | 2 +- 2 files changed, 1 insertion(+), 16 deletions(-) diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h index 88065e3..8b40a83 100644 --- a/arch/x86/include/asm/i387.h +++ b/arch/x86/include/asm/i387.h @@ -387,19 +387,6 @@ static inline void irq_ts_restore(int TS_state) stts(); } -#ifdef CONFIG_X86_64 - -static inline void save_init_fpu(struct task_struct *tsk) -{ - __save_init_fpu(tsk); - stts(); -} - -#define unlazy_fpu __unlazy_fpu -#define clear_fpu __clear_fpu - -#else /* CONFIG_X86_32 */ - /* * These disable preemption on their own and are safe */ @@ -425,8 +412,6 @@ static inline void clear_fpu(struct task_struct *tsk) preempt_enable(); } -#endif /* CONFIG_X86_64 */ - /* * i387 state interaction */ diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 3d9ea53..b3d7a3a 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -424,7 +424,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) load_TLS(next, cpu); /* Must be after DS reload */ - unlazy_fpu(prev_p); + __unlazy_fpu(prev_p); /* Make sure cpu is ready for new context */ if (preload_fpu) -- 2.7.4