| Message ID | 1342462640-18410-1-git-send-email-ccross@android.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, 16 Jul 2012, Colin Cross wrote: > vfp_pm_suspend should save the VFP state in suspend after > any lazy context switch. If it only saves when the VFP is enabled, > the state can get lost when, on a UP system: > Thread 1 uses the VFP > Context switch occurs to thread 2, VFP is disabled but the > VFP context is not saved > Thread 2 initiates suspend > vfp_pm_suspend is called with the VFP disabled, and the unsaved > VFP context of Thread 1 in the registers > > Modify vfp_pm_suspend to save the VFP context whenever > vfp_current_hw_state is not NULL. > > Includes a fix from Ido Yariv <ido@wizery.com>, who pointed out that on > SMP systems, the state pointer can be pointing to a freed task struct if > a task exited on another cpu, fixed by using #ifdef CONFIG_SMP in the > new if clause. > > Cc: Russell King <linux@arm.linux.org.uk> > Cc: Barry Song <bs14@csr.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Ido Yariv <ido@wizery.com> > Cc: Daniel Drake <dsd@laptop.org> > Cc: Will Deacon <will.deacon@arm.com> > Signed-off-by: Colin Cross <ccross@android.com> > --- > arch/arm/vfp/vfpmodule.c | 6 ++++++ > 1 files changed, 6 insertions(+), 0 deletions(-) > > diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c > index 58696192..ce55f05 100644 > --- a/arch/arm/vfp/vfpmodule.c > +++ b/arch/arm/vfp/vfpmodule.c > @@ -457,6 +457,12 @@ static int vfp_pm_suspend(void) > > /* disable, just in case */ > fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN); > + } else if (vfp_current_hw_state[ti->cpu]) { > +#ifndef CONFIG_SMP > + fmxr(FPEXC, fpexc | FPEXC_EN); > + vfp_save_state(vfp_current_hw_state[ti->cpu], fpexc); > + fmxr(FPEXC, fpexc); > +#endif > } Couldn't vfp_sync_hwstate() be used here instead? Nicolas
On Mon, Jul 16, 2012 at 11:34 AM, Nicolas Pitre <nicolas.pitre@linaro.org> wrote: > On Mon, 16 Jul 2012, Colin Cross wrote: > >> vfp_pm_suspend should save the VFP state in suspend after >> any lazy context switch. If it only saves when the VFP is enabled, >> the state can get lost when, on a UP system: >> Thread 1 uses the VFP >> Context switch occurs to thread 2, VFP is disabled but the >> VFP context is not saved >> Thread 2 initiates suspend >> vfp_pm_suspend is called with the VFP disabled, and the unsaved >> VFP context of Thread 1 in the registers >> >> Modify vfp_pm_suspend to save the VFP context whenever >> vfp_current_hw_state is not NULL. >> >> Includes a fix from Ido Yariv <ido@wizery.com>, who pointed out that on >> SMP systems, the state pointer can be pointing to a freed task struct if >> a task exited on another cpu, fixed by using #ifdef CONFIG_SMP in the >> new if clause. >> >> Cc: Russell King <linux@arm.linux.org.uk> >> Cc: Barry Song <bs14@csr.com> >> Cc: Catalin Marinas <catalin.marinas@arm.com> >> Cc: Ido Yariv <ido@wizery.com> >> Cc: Daniel Drake <dsd@laptop.org> >> Cc: Will Deacon <will.deacon@arm.com> >> Signed-off-by: Colin Cross <ccross@android.com> >> --- >> arch/arm/vfp/vfpmodule.c | 6 ++++++ >> 1 files changed, 6 insertions(+), 0 deletions(-) >> >> diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c >> index 58696192..ce55f05 100644 >> --- a/arch/arm/vfp/vfpmodule.c >> +++ b/arch/arm/vfp/vfpmodule.c >> @@ -457,6 +457,12 @@ static int vfp_pm_suspend(void) >> >> /* disable, just in case */ >> fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN); >> + } else if (vfp_current_hw_state[ti->cpu]) { >> +#ifndef CONFIG_SMP >> + fmxr(FPEXC, fpexc | FPEXC_EN); >> + vfp_save_state(vfp_current_hw_state[ti->cpu], fpexc); >> + fmxr(FPEXC, fpexc); >> +#endif >> } > > Couldn't vfp_sync_hwstate() be used here instead? Not easily, we don't have the thread struct of the thread that is in the vfp hardware. We would have to read vfp_current_hw_state for the current cpu and use container_of to get from struct vfpstate to struct thread_info, and then pass that back in to vfp_sync_hwstate.
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c index 58696192..ce55f05 100644 --- a/arch/arm/vfp/vfpmodule.c +++ b/arch/arm/vfp/vfpmodule.c @@ -457,6 +457,12 @@ static int vfp_pm_suspend(void) /* disable, just in case */ fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN); + } else if (vfp_current_hw_state[ti->cpu]) { +#ifndef CONFIG_SMP + fmxr(FPEXC, fpexc | FPEXC_EN); + vfp_save_state(vfp_current_hw_state[ti->cpu], fpexc); + fmxr(FPEXC, fpexc); +#endif } /* clear any information we had about last context state */
vfp_pm_suspend should save the VFP state in suspend after any lazy context switch. If it only saves when the VFP is enabled, the state can get lost when, on a UP system: Thread 1 uses the VFP Context switch occurs to thread 2, VFP is disabled but the VFP context is not saved Thread 2 initiates suspend vfp_pm_suspend is called with the VFP disabled, and the unsaved VFP context of Thread 1 in the registers Modify vfp_pm_suspend to save the VFP context whenever vfp_current_hw_state is not NULL. Includes a fix from Ido Yariv <ido@wizery.com>, who pointed out that on SMP systems, the state pointer can be pointing to a freed task struct if a task exited on another cpu, fixed by using #ifdef CONFIG_SMP in the new if clause. Cc: Russell King <linux@arm.linux.org.uk> Cc: Barry Song <bs14@csr.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Ido Yariv <ido@wizery.com> Cc: Daniel Drake <dsd@laptop.org> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Colin Cross <ccross@android.com> --- arch/arm/vfp/vfpmodule.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-)