From 797245f5da543074ee7db0e0516da744c89aa17f Mon Sep 17 00:00:00 2001 From: Russell King Date: Fri, 18 Dec 2009 14:34:43 +0000 Subject: [PATCH] ARM: Convert VFP/Crunch/XscaleCP thread_release() to exit_thread() This avoids races in the VFP code where the dead thread may have state on another CPU. By moving this code to exit_thread(), we will be running as the thread, and therefore be running on the current CPU. This means that we can ensure that the only local state is accessed in the thread notifiers. Acked-by: Catalin Marinas Signed-off-by: Russell King --- arch/arm/include/asm/thread_notify.h | 2 +- arch/arm/kernel/crunch.c | 2 +- arch/arm/kernel/process.c | 12 +++++------- arch/arm/kernel/xscale-cp0.c | 2 +- arch/arm/vfp/vfpmodule.c | 19 +++++++++++-------- 5 files changed, 19 insertions(+), 18 deletions(-) diff --git a/arch/arm/include/asm/thread_notify.h b/arch/arm/include/asm/thread_notify.h index f27379d7f72..c4391ba2035 100644 --- a/arch/arm/include/asm/thread_notify.h +++ b/arch/arm/include/asm/thread_notify.h @@ -41,7 +41,7 @@ static inline void thread_notify(unsigned long rc, struct thread_info *thread) * These are the reason codes for the thread notifier. */ #define THREAD_NOTIFY_FLUSH 0 -#define THREAD_NOTIFY_RELEASE 1 +#define THREAD_NOTIFY_EXIT 1 #define THREAD_NOTIFY_SWITCH 2 #endif diff --git a/arch/arm/kernel/crunch.c b/arch/arm/kernel/crunch.c index 769abe15cf9..25ef223ba7f 100644 --- a/arch/arm/kernel/crunch.c +++ b/arch/arm/kernel/crunch.c @@ -51,7 +51,7 @@ static int crunch_do(struct notifier_block *self, unsigned long cmd, void *t) * initialised state information on the first fault. */ - case THREAD_NOTIFY_RELEASE: + case THREAD_NOTIFY_EXIT: crunch_task_release(thread); break; diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c index 0d96d0171c0..67304138a2c 100644 --- a/arch/arm/kernel/process.c +++ b/arch/arm/kernel/process.c @@ -274,17 +274,18 @@ void show_regs(struct pt_regs * regs) __backtrace(); } +ATOMIC_NOTIFIER_HEAD(thread_notify_head); + +EXPORT_SYMBOL_GPL(thread_notify_head); + /* * Free current thread data structures etc.. */ void exit_thread(void) { + thread_notify(THREAD_NOTIFY_EXIT, current_thread_info()); } -ATOMIC_NOTIFIER_HEAD(thread_notify_head); - -EXPORT_SYMBOL_GPL(thread_notify_head); - void flush_thread(void) { struct thread_info *thread = current_thread_info(); @@ -299,9 +300,6 @@ void flush_thread(void) void release_thread(struct task_struct *dead_task) { - struct thread_info *thread = task_thread_info(dead_task); - - thread_notify(THREAD_NOTIFY_RELEASE, thread); } asmlinkage void ret_from_fork(void) __asm__("ret_from_fork"); diff --git a/arch/arm/kernel/xscale-cp0.c b/arch/arm/kernel/xscale-cp0.c index 17127db906f..1796157e3dd 100644 --- a/arch/arm/kernel/xscale-cp0.c +++ b/arch/arm/kernel/xscale-cp0.c @@ -70,7 +70,7 @@ static int iwmmxt_do(struct notifier_block *self, unsigned long cmd, void *t) * initialised state information on the first fault. */ - case THREAD_NOTIFY_RELEASE: + case THREAD_NOTIFY_EXIT: iwmmxt_task_release(thread); break; diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c index aed05bc3c2e..f60a5400a25 100644 --- a/arch/arm/vfp/vfpmodule.c +++ b/arch/arm/vfp/vfpmodule.c @@ -63,14 +63,15 @@ static void vfp_thread_flush(struct thread_info *thread) put_cpu(); } -static void vfp_thread_release(struct thread_info *thread) +static void vfp_thread_exit(struct thread_info *thread) { /* release case: Per-thread VFP cleanup. */ union vfp_state *vfp = &thread->vfpstate; - unsigned int cpu = thread->cpu; + unsigned int cpu = get_cpu(); if (last_VFP_context[cpu] == vfp) last_VFP_context[cpu] = NULL; + put_cpu(); } /* @@ -88,11 +89,13 @@ static void vfp_thread_release(struct thread_info *thread) * but may change at any time. * - we could be preempted if tree preempt rcu is enabled, so * it is unsafe to use thread->cpu. - * THREAD_NOTIFY_RELEASE: - * - the thread (v) will not be running on any CPU; it is a dead thread. - * - thread->cpu will be the last CPU the thread ran on, which may not - * be the current CPU. - * - we could be preempted if tree preempt rcu is enabled. + * THREAD_NOTIFY_EXIT + * - the thread (v) will be running on the local CPU, so + * v === current_thread_info() + * - thread->cpu is the local CPU number at the time it is accessed, + * but may change at any time. + * - we could be preempted if tree preempt rcu is enabled, so + * it is unsafe to use thread->cpu. */ static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v) { @@ -133,7 +136,7 @@ static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v) if (cmd == THREAD_NOTIFY_FLUSH) vfp_thread_flush(thread); else - vfp_thread_release(thread); + vfp_thread_exit(thread); return NOTIFY_DONE; }