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| author |   Linus Torvalds <torvalds@linux-foundation.org> | 2012-02-20 10:24:09 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-02-20 10:24:09 -0800 |
| commit | cea20ca3f3181fc36788a15bc65d1062b96a0a6c (patch) | |
| tree | 86c646c0d228d1fe265536b81d86af406ff92c8e /arch/x86 | |
| parent | Linux 3.3-rc4 (diff) | |
| download | linux-dev-cea20ca3f3181fc36788a15bc65d1062b96a0a6c.tar.xz linux-dev-cea20ca3f3181fc36788a15bc65d1062b96a0a6c.zip | |
i387: fix up some fpu_counter confusion
This makes sure we clear the FPU usage counter for newly created tasks,
just so that we start off in a known state (for example, don't try to
preload the FPU state on the first task switch etc).
It also fixes a thinko in when we increment the fpu_counter at task
switch time, introduced by commit 34ddc81a230b ("i387: re-introduce FPU
state preloading at context switch time"). We should increment the
*new* task fpu_counter, not the old task, and only if we decide to use
that state (whether lazily or preloaded).
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/include/asm/i387.h | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/process_32.c | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/process_64.c | 1 |
3 files changed, 4 insertions, 1 deletions
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h index a850b4d8d14d..8df95849721d 100644 --- a/arch/x86/include/asm/i387.h +++ b/arch/x86/include/asm/i387.h @@ -348,10 +348,10 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta if (__save_init_fpu(old)) fpu_lazy_state_intact(old); __thread_clear_has_fpu(old); - old->fpu_counter++; /* Don't change CR0.TS if we just switch! */ if (fpu.preload) { + new->fpu_counter++; __thread_set_has_fpu(new); prefetch(new->thread.fpu.state); } else @@ -359,6 +359,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta } else { old->fpu_counter = 0; if (fpu.preload) { + new->fpu_counter++; if (fpu_lazy_restore(new)) fpu.preload = 0; else diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index 80bfe1ab0031..bc32761bc27a 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -214,6 +214,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, task_user_gs(p) = get_user_gs(regs); + p->fpu_counter = 0; p->thread.io_bitmap_ptr = NULL; tsk = current; err = -ENOMEM; diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 1fd94bc4279d..8ad880b3bc1c 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -286,6 +286,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, set_tsk_thread_flag(p, TIF_FORK); + p->fpu_counter = 0; p->thread.io_bitmap_ptr = NULL; savesegment(gs, p->thread.gsindex); |