| Message ID | 1422990417-1783-3-git-send-email-daniel.thompson@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
On Tue, 3 Feb 2015, Daniel Thompson wrote: > It is currently possible for FIQ handlers to re-enter gic_raise_softirq() > and lock up. > > gic_raise_softirq() > lock(x); > -~-> FIQ > handle_fiq() > gic_raise_softirq() > lock(x); <-- Lockup > > arch/arm/ uses IPIs to implement arch_irq_work_raise(), thus this issue > renders it difficult for FIQ handlers to safely defer work to less > restrictive calling contexts. > > This patch fixes the problem by converting the cpu_map_migration_lock > into a rwlock making it safe to re-enter the function. > > Note that having made it safe to re-enter gic_raise_softirq() we no > longer need to mask interrupts during gic_raise_softirq() because the > b.L migration is always performed from task context. Very good point. Once my concerns on patch #1 are addressed, you may add my ACK to this one. > Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Jason Cooper <jason@lakedaemon.net> > Cc: Russell King <linux@arm.linux.org.uk> > Cc: Marc Zyngier <marc.zyngier@arm.com> > --- > drivers/irqchip/irq-gic.c | 38 +++++++++++++++++++++++++------------- > 1 file changed, 25 insertions(+), 13 deletions(-) > > diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c > index a9ed64dcc84b..c172176499f6 100644 > --- a/drivers/irqchip/irq-gic.c > +++ b/drivers/irqchip/irq-gic.c > @@ -75,22 +75,25 @@ static DEFINE_RAW_SPINLOCK(irq_controller_lock); > /* > * This lock is used by the big.LITTLE migration code to ensure no IPIs > * can be pended on the old core after the map has been updated. > + * > + * This lock may be locked for reading from both IRQ and FIQ handlers > + * and therefore must not be locked for writing when these are enabled. > */ > #ifdef CONFIG_BL_SWITCHER > -static DEFINE_RAW_SPINLOCK(cpu_map_migration_lock); > +static DEFINE_RWLOCK(cpu_map_migration_lock); > > -static inline void bl_migration_lock(unsigned long *flags) > +static inline void bl_migration_lock(void) > { > - raw_spin_lock_irqsave(&cpu_map_migration_lock, *flags); > + read_lock(&cpu_map_migration_lock); > } > > -static inline void bl_migration_unlock(unsigned long flags) > +static inline void bl_migration_unlock(void) > { > - raw_spin_unlock_irqrestore(&cpu_map_migration_lock, flags); > + read_unlock(&cpu_map_migration_lock); > } > #else > -static inline void bl_migration_lock(unsigned long *flags) {} > -static inline void bl_migration_unlock(unsigned long flags) {} > +static inline void bl_migration_lock(void) {} > +static inline void bl_migration_unlock(void) {} > #endif > > /* > @@ -640,12 +643,20 @@ static void __init gic_pm_init(struct gic_chip_data *gic) > #endif > > #ifdef CONFIG_SMP > +/* > + * Raise the specified IPI on all cpus set in mask. > + * > + * This function is safe to call from all calling contexts, including > + * FIQ handlers. It relies on bl_migration_lock() being multiply acquirable > + * to avoid deadlocks when the function is re-entered at different > + * exception levels. > + */ > static void gic_raise_softirq(const struct cpumask *mask, unsigned int irq) > { > int cpu; > - unsigned long flags, map = 0; > + unsigned long map = 0; > > - bl_migration_lock(&flags); > + bl_migration_lock(); > > /* Convert our logical CPU mask into a physical one. */ > for_each_cpu(cpu, mask) > @@ -660,7 +671,7 @@ static void gic_raise_softirq(const struct cpumask *mask, unsigned int irq) > /* this always happens on GIC0 */ > writel_relaxed(map << 16 | irq, gic_data_dist_base(&gic_data[0]) + GIC_DIST_SOFTINT); > > - bl_migration_unlock(flags); > + bl_migration_unlock(); > } > #endif > > @@ -708,7 +719,8 @@ int gic_get_cpu_id(unsigned int cpu) > * Migrate all peripheral interrupts with a target matching the current CPU > * to the interface corresponding to @new_cpu_id. The CPU interface mapping > * is also updated. Targets to other CPU interfaces are unchanged. > - * This must be called with IRQs locally disabled. > + * This must be called from a task context and with IRQ and FIQ locally > + * disabled. > */ > void gic_migrate_target(unsigned int new_cpu_id) > { > @@ -739,9 +751,9 @@ void gic_migrate_target(unsigned int new_cpu_id) > * pending on the old cpu static. That means we can defer the > * migration until after we have released the irq_controller_lock. > */ > - raw_spin_lock(&cpu_map_migration_lock); > + write_lock(&cpu_map_migration_lock); > gic_cpu_map[cpu] = 1 << new_cpu_id; > - raw_spin_unlock(&cpu_map_migration_lock); > + write_unlock(&cpu_map_migration_lock); > > /* > * Find all the peripheral interrupts targetting the current > -- > 1.9.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > >
diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c index a9ed64dcc84b..c172176499f6 100644 --- a/drivers/irqchip/irq-gic.c +++ b/drivers/irqchip/irq-gic.c @@ -75,22 +75,25 @@ static DEFINE_RAW_SPINLOCK(irq_controller_lock); /* * This lock is used by the big.LITTLE migration code to ensure no IPIs * can be pended on the old core after the map has been updated. + * + * This lock may be locked for reading from both IRQ and FIQ handlers + * and therefore must not be locked for writing when these are enabled. */ #ifdef CONFIG_BL_SWITCHER -static DEFINE_RAW_SPINLOCK(cpu_map_migration_lock); +static DEFINE_RWLOCK(cpu_map_migration_lock); -static inline void bl_migration_lock(unsigned long *flags) +static inline void bl_migration_lock(void) { - raw_spin_lock_irqsave(&cpu_map_migration_lock, *flags); + read_lock(&cpu_map_migration_lock); } -static inline void bl_migration_unlock(unsigned long flags) +static inline void bl_migration_unlock(void) { - raw_spin_unlock_irqrestore(&cpu_map_migration_lock, flags); + read_unlock(&cpu_map_migration_lock); } #else -static inline void bl_migration_lock(unsigned long *flags) {} -static inline void bl_migration_unlock(unsigned long flags) {} +static inline void bl_migration_lock(void) {} +static inline void bl_migration_unlock(void) {} #endif /* @@ -640,12 +643,20 @@ static void __init gic_pm_init(struct gic_chip_data *gic) #endif #ifdef CONFIG_SMP +/* + * Raise the specified IPI on all cpus set in mask. + * + * This function is safe to call from all calling contexts, including + * FIQ handlers. It relies on bl_migration_lock() being multiply acquirable + * to avoid deadlocks when the function is re-entered at different + * exception levels. + */ static void gic_raise_softirq(const struct cpumask *mask, unsigned int irq) { int cpu; - unsigned long flags, map = 0; + unsigned long map = 0; - bl_migration_lock(&flags); + bl_migration_lock(); /* Convert our logical CPU mask into a physical one. */ for_each_cpu(cpu, mask) @@ -660,7 +671,7 @@ static void gic_raise_softirq(const struct cpumask *mask, unsigned int irq) /* this always happens on GIC0 */ writel_relaxed(map << 16 | irq, gic_data_dist_base(&gic_data[0]) + GIC_DIST_SOFTINT); - bl_migration_unlock(flags); + bl_migration_unlock(); } #endif @@ -708,7 +719,8 @@ int gic_get_cpu_id(unsigned int cpu) * Migrate all peripheral interrupts with a target matching the current CPU * to the interface corresponding to @new_cpu_id. The CPU interface mapping * is also updated. Targets to other CPU interfaces are unchanged. - * This must be called with IRQs locally disabled. + * This must be called from a task context and with IRQ and FIQ locally + * disabled. */ void gic_migrate_target(unsigned int new_cpu_id) { @@ -739,9 +751,9 @@ void gic_migrate_target(unsigned int new_cpu_id) * pending on the old cpu static. That means we can defer the * migration until after we have released the irq_controller_lock. */ - raw_spin_lock(&cpu_map_migration_lock); + write_lock(&cpu_map_migration_lock); gic_cpu_map[cpu] = 1 << new_cpu_id; - raw_spin_unlock(&cpu_map_migration_lock); + write_unlock(&cpu_map_migration_lock); /* * Find all the peripheral interrupts targetting the current
It is currently possible for FIQ handlers to re-enter gic_raise_softirq() and lock up. gic_raise_softirq() lock(x); -~-> FIQ handle_fiq() gic_raise_softirq() lock(x); <-- Lockup arch/arm/ uses IPIs to implement arch_irq_work_raise(), thus this issue renders it difficult for FIQ handlers to safely defer work to less restrictive calling contexts. This patch fixes the problem by converting the cpu_map_migration_lock into a rwlock making it safe to re-enter the function. Note that having made it safe to re-enter gic_raise_softirq() we no longer need to mask interrupts during gic_raise_softirq() because the b.L migration is always performed from task context. Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Jason Cooper <jason@lakedaemon.net> Cc: Russell King <linux@arm.linux.org.uk> Cc: Marc Zyngier <marc.zyngier@arm.com> --- drivers/irqchip/irq-gic.c | 38 +++++++++++++++++++++++++------------- 1 file changed, 25 insertions(+), 13 deletions(-)