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Suresh Siddha 870568b390 x86, fpu: fix CONFIG_PREEMPT=y corruption of application's FPU stack ... Jürgen Mell reported an FPU state corruption bug under CONFIG_PREEMPT, and bisected it to commit v2.6.19-1363-gacc2076, "i386: add sleazy FPU optimization". Add tsk_used_math() checks to prevent calling math_state_restore() which can sleep in the case of !tsk_used_math(). This prevents making a blocking call in __switch_to(). Apparently "fpu_counter > 5" check is not enough, as in some signal handling and fork/exec scenarios, fpu_counter > 5 and !tsk_used_math() is possible. It's a side effect though. This is the failing scenario: process 'A' in save_i387_ia32() just after clear_used_math() Got an interrupt and pre-empted out. At the next context switch to process 'A' again, kernel tries to restore the math state proactively and sees a fpu_counter > 0 and !tsk_used_math() This results in init_fpu() during the __switch_to()'s math_state_restore() And resulting in fpu corruption which will be saved/restored (save_i387_fxsave and restore_i387_fxsave) during the remaining part of the signal handling after the context switch. Bisected-by: Jürgen Mell <j.mell@t-online.de> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Tested-by: Jürgen Mell <j.mell@t-online.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@kernel.org		17 years ago
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boot	…
configs	…
crypto	…
ia32	…
kernel	x86, fpu: fix CONFIG_PREEMPT=y corruption of application's FPU stack	17 years ago
kvm	…
lguest	lguest: fix ugly <NULL> in /proc/interrupts	17 years ago
lib	x86: enable preemption in delay	17 years ago
mach-default	…
mach-es7000	…
mach-generic	…
mach-rdc321x	…
mach-visws	…
mach-voyager	…
math-emu	x86: fix broken math-emu with lazy allocation of fpu area	17 years ago
mm	x86: section mismatch fix	17 years ago
oprofile	…
pci	…
power	…
vdso	…
video	…
xen	…
Kconfig	Kconfig: introduce ARCH_DEFCONFIG to DEFCONFIG_LIST	17 years ago
Kconfig.cpu	…
Kconfig.debug	…
Makefile	…
Makefile_32.cpu	…