From 750d857c682f4db60d14722d430c7ccc35070962 Mon Sep 17 00:00:00 2001 From: Robert Richter Date: Fri, 13 Aug 2010 16:29:04 +0200 Subject: [PATCH 1/3] oprofile: fix crash when accessing freed task structs This patch fixes a crash during shutdown reported below. The crash is caused by accessing already freed task structs. The fix changes the order for registering and unregistering notifier callbacks. All notifiers must be initialized before buffers start working. To stop buffer synchronization we cancel all workqueues, unregister the notifier callback and then flush all buffers. After all of this we finally can free all tasks listed. This should avoid accessing freed tasks. On 22.07.10 01:14:40, Benjamin Herrenschmidt wrote: > So the initial observation is a spinlock bad magic followed by a crash > in the spinlock debug code: > > [ 1541.586531] BUG: spinlock bad magic on CPU#5, events/5/136 > [ 1541.597564] Unable to handle kernel paging request for data at address 0x6b6b6b6b6b6b6d03 > > Backtrace looks like: > > spin_bug+0x74/0xd4 > ._raw_spin_lock+0x48/0x184 > ._spin_lock+0x10/0x24 > .get_task_mm+0x28/0x8c > .sync_buffer+0x1b4/0x598 > .wq_sync_buffer+0xa0/0xdc > .worker_thread+0x1d8/0x2a8 > .kthread+0xa8/0xb4 > .kernel_thread+0x54/0x70 > > So we are accessing a freed task struct in the work queue when > processing the samples. Reported-by: Benjamin Herrenschmidt Cc: stable@kernel.org Signed-off-by: Robert Richter --- drivers/oprofile/buffer_sync.c | 27 ++++++++++++++------------- drivers/oprofile/cpu_buffer.c | 2 -- 2 files changed, 14 insertions(+), 15 deletions(-) diff --git a/drivers/oprofile/buffer_sync.c b/drivers/oprofile/buffer_sync.c index a9352b2c7ac4..b7e755f4178a 100644 --- a/drivers/oprofile/buffer_sync.c +++ b/drivers/oprofile/buffer_sync.c @@ -141,16 +141,6 @@ static struct notifier_block module_load_nb = { .notifier_call = module_load_notify, }; - -static void end_sync(void) -{ - end_cpu_work(); - /* make sure we don't leak task structs */ - process_task_mortuary(); - process_task_mortuary(); -} - - int sync_start(void) { int err; @@ -158,7 +148,7 @@ int sync_start(void) if (!zalloc_cpumask_var(&marked_cpus, GFP_KERNEL)) return -ENOMEM; - start_cpu_work(); + mutex_lock(&buffer_mutex); err = task_handoff_register(&task_free_nb); if (err) @@ -173,7 +163,10 @@ int sync_start(void) if (err) goto out4; + start_cpu_work(); + out: + mutex_unlock(&buffer_mutex); return err; out4: profile_event_unregister(PROFILE_MUNMAP, &munmap_nb); @@ -182,7 +175,6 @@ int sync_start(void) out2: task_handoff_unregister(&task_free_nb); out1: - end_sync(); free_cpumask_var(marked_cpus); goto out; } @@ -190,11 +182,20 @@ int sync_start(void) void sync_stop(void) { + /* flush buffers */ + mutex_lock(&buffer_mutex); + end_cpu_work(); unregister_module_notifier(&module_load_nb); profile_event_unregister(PROFILE_MUNMAP, &munmap_nb); profile_event_unregister(PROFILE_TASK_EXIT, &task_exit_nb); task_handoff_unregister(&task_free_nb); - end_sync(); + mutex_unlock(&buffer_mutex); + flush_scheduled_work(); + + /* make sure we don't leak task structs */ + process_task_mortuary(); + process_task_mortuary(); + free_cpumask_var(marked_cpus); } diff --git a/drivers/oprofile/cpu_buffer.c b/drivers/oprofile/cpu_buffer.c index 219f79e2210a..f179ac2ea801 100644 --- a/drivers/oprofile/cpu_buffer.c +++ b/drivers/oprofile/cpu_buffer.c @@ -120,8 +120,6 @@ void end_cpu_work(void) cancel_delayed_work(&b->work); } - - flush_scheduled_work(); } /* From 10f0412f57f2a76a90eff4376f59cbb0a39e4e18 Mon Sep 17 00:00:00 2001 From: Robert Richter Date: Mon, 30 Aug 2010 10:56:18 +0200 Subject: [PATCH 2/3] oprofile, x86: fix init_sysfs error handling On failure init_sysfs() might not properly free resources. The error code of the function is not checked. And, when reinitializing the exit function might be called twice. This patch fixes all this. Cc: stable@kernel.org Signed-off-by: Robert Richter --- arch/x86/oprofile/nmi_int.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c index f6b48f6c5951..73a41d3c6c09 100644 --- a/arch/x86/oprofile/nmi_int.c +++ b/arch/x86/oprofile/nmi_int.c @@ -568,8 +568,13 @@ static int __init init_sysfs(void) int error; error = sysdev_class_register(&oprofile_sysclass); - if (!error) - error = sysdev_register(&device_oprofile); + if (error) + return error; + + error = sysdev_register(&device_oprofile); + if (error) + sysdev_class_unregister(&oprofile_sysclass); + return error; } @@ -695,6 +700,8 @@ int __init op_nmi_init(struct oprofile_operations *ops) char *cpu_type = NULL; int ret = 0; + using_nmi = 0; + if (!cpu_has_apic) return -ENODEV; @@ -774,7 +781,10 @@ int __init op_nmi_init(struct oprofile_operations *ops) mux_init(ops); - init_sysfs(); + ret = init_sysfs(); + if (ret) + return ret; + using_nmi = 1; printk(KERN_INFO "oprofile: using NMI interrupt.\n"); return 0; From 269f45c25028c75fe10e6d9be86e7202ab461fbc Mon Sep 17 00:00:00 2001 From: Robert Richter Date: Wed, 1 Sep 2010 14:50:50 +0200 Subject: [PATCH 3/3] oprofile, x86: fix init_sysfs() function stub MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The use of the return value of init_sysfs() with commit 10f0412 oprofile, x86: fix init_sysfs error handling discovered the following build error for !CONFIG_PM: .../linux/arch/x86/oprofile/nmi_int.c: In function ‘op_nmi_init’: .../linux/arch/x86/oprofile/nmi_int.c:784: error: expected expression before ‘do’ make[2]: *** [arch/x86/oprofile/nmi_int.o] Error 1 make[1]: *** [arch/x86/oprofile] Error 2 This patch fixes this. Reported-by: Ingo Molnar Cc: stable@kernel.org Signed-off-by: Robert Richter --- arch/x86/oprofile/nmi_int.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c index 73a41d3c6c09..cfe4faabb0f6 100644 --- a/arch/x86/oprofile/nmi_int.c +++ b/arch/x86/oprofile/nmi_int.c @@ -585,8 +585,10 @@ static void exit_sysfs(void) } #else -#define init_sysfs() do { } while (0) -#define exit_sysfs() do { } while (0) + +static inline int init_sysfs(void) { return 0; } +static inline void exit_sysfs(void) { } + #endif /* CONFIG_PM */ static int __init p4_init(char **cpu_type)