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>
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index a850b4d..8df9584 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -348,10 +348,10 @@
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 @@
} 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 80bfe1a..bc32761 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -214,6 +214,7 @@
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 1fd94bc..8ad880b 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -286,6 +286,7 @@
set_tsk_thread_flag(p, TIF_FORK);
+ p->fpu_counter = 0;
p->thread.io_bitmap_ptr = NULL;
savesegment(gs, p->thread.gsindex);