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 34ddc81a23
("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>
This commit is contained in:
parent
b01543dfe6
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@ -348,10 +348,10 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
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if (__save_init_fpu(old))
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fpu_lazy_state_intact(old);
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__thread_clear_has_fpu(old);
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old->fpu_counter++;
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/* Don't change CR0.TS if we just switch! */
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if (fpu.preload) {
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new->fpu_counter++;
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__thread_set_has_fpu(new);
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prefetch(new->thread.fpu.state);
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} else
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@ -359,6 +359,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
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} else {
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old->fpu_counter = 0;
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if (fpu.preload) {
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new->fpu_counter++;
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if (fpu_lazy_restore(new))
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fpu.preload = 0;
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else
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@ -214,6 +214,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
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task_user_gs(p) = get_user_gs(regs);
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p->fpu_counter = 0;
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p->thread.io_bitmap_ptr = NULL;
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tsk = current;
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err = -ENOMEM;
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@ -286,6 +286,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
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set_tsk_thread_flag(p, TIF_FORK);
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p->fpu_counter = 0;
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p->thread.io_bitmap_ptr = NULL;
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savesegment(gs, p->thread.gsindex);
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