From a6fa941d94b411bbd2b6421ffbde6db3c93e65ab Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 20 Aug 2012 14:59:25 +0100 Subject: perf_event: Switch to internal refcount, fix race with close() Don't mess with file refcounts (or keep a reference to file, for that matter) in perf_event. Use explicit refcount of its own instead. Deal with the race between the final reference to event going away and new children getting created for it by use of atomic_long_inc_not_zero() in inherit_event(); just have the latter free what it had allocated and return NULL, that works out just fine (children of siblings of something doomed are created as singletons, same as if the child of leader had been created and immediately killed). Signed-off-by: Al Viro Cc: stable@kernel.org Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20120820135925.GG23464@ZenIV.linux.org.uk Signed-off-by: Ingo Molnar --- kernel/events/core.c | 62 ++++++++++++++++++++++++++++------------------------ 1 file changed, 33 insertions(+), 29 deletions(-) (limited to 'kernel/events/core.c') diff --git a/kernel/events/core.c b/kernel/events/core.c index b7935fcec7d9..efef4282b8e8 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2935,12 +2935,12 @@ EXPORT_SYMBOL_GPL(perf_event_release_kernel); /* * Called when the last reference to the file is gone. */ -static int perf_release(struct inode *inode, struct file *file) +static void put_event(struct perf_event *event) { - struct perf_event *event = file->private_data; struct task_struct *owner; - file->private_data = NULL; + if (!atomic_long_dec_and_test(&event->refcount)) + return; rcu_read_lock(); owner = ACCESS_ONCE(event->owner); @@ -2975,7 +2975,13 @@ static int perf_release(struct inode *inode, struct file *file) put_task_struct(owner); } - return perf_event_release_kernel(event); + perf_event_release_kernel(event); +} + +static int perf_release(struct inode *inode, struct file *file) +{ + put_event(file->private_data); + return 0; } u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running) @@ -3227,7 +3233,7 @@ unlock: static const struct file_operations perf_fops; -static struct perf_event *perf_fget_light(int fd, int *fput_needed) +static struct file *perf_fget_light(int fd, int *fput_needed) { struct file *file; @@ -3241,7 +3247,7 @@ static struct perf_event *perf_fget_light(int fd, int *fput_needed) return ERR_PTR(-EBADF); } - return file->private_data; + return file; } static int perf_event_set_output(struct perf_event *event, @@ -3273,19 +3279,21 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg) case PERF_EVENT_IOC_SET_OUTPUT: { + struct file *output_file = NULL; struct perf_event *output_event = NULL; int fput_needed = 0; int ret; if (arg != -1) { - output_event = perf_fget_light(arg, &fput_needed); - if (IS_ERR(output_event)) - return PTR_ERR(output_event); + output_file = perf_fget_light(arg, &fput_needed); + if (IS_ERR(output_file)) + return PTR_ERR(output_file); + output_event = output_file->private_data; } ret = perf_event_set_output(event, output_event); if (output_event) - fput_light(output_event->filp, fput_needed); + fput_light(output_file, fput_needed); return ret; } @@ -5950,6 +5958,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu, mutex_init(&event->mmap_mutex); + atomic_long_set(&event->refcount, 1); event->cpu = cpu; event->attr = *attr; event->group_leader = group_leader; @@ -6260,12 +6269,12 @@ SYSCALL_DEFINE5(perf_event_open, return event_fd; if (group_fd != -1) { - group_leader = perf_fget_light(group_fd, &fput_needed); - if (IS_ERR(group_leader)) { - err = PTR_ERR(group_leader); + group_file = perf_fget_light(group_fd, &fput_needed); + if (IS_ERR(group_file)) { + err = PTR_ERR(group_file); goto err_fd; } - group_file = group_leader->filp; + group_leader = group_file->private_data; if (flags & PERF_FLAG_FD_OUTPUT) output_event = group_leader; if (flags & PERF_FLAG_FD_NO_GROUP) @@ -6402,7 +6411,6 @@ SYSCALL_DEFINE5(perf_event_open, put_ctx(gctx); } - event->filp = event_file; WARN_ON_ONCE(ctx->parent_ctx); mutex_lock(&ctx->mutex); @@ -6496,7 +6504,6 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu, goto err_free; } - event->filp = NULL; WARN_ON_ONCE(ctx->parent_ctx); mutex_lock(&ctx->mutex); perf_install_in_context(ctx, event, cpu); @@ -6578,7 +6585,7 @@ static void sync_child_event(struct perf_event *child_event, * Release the parent event, if this was the last * reference to it. */ - fput(parent_event->filp); + put_event(parent_event); } static void @@ -6654,9 +6661,8 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn) * * __perf_event_exit_task() * sync_child_event() - * fput(parent_event->filp) - * perf_release() - * mutex_lock(&ctx->mutex) + * put_event() + * mutex_lock(&ctx->mutex) * * But since its the parent context it won't be the same instance. */ @@ -6724,7 +6730,7 @@ static void perf_free_event(struct perf_event *event, list_del_init(&event->child_list); mutex_unlock(&parent->child_mutex); - fput(parent->filp); + put_event(parent); perf_group_detach(event); list_del_event(event, ctx); @@ -6804,6 +6810,12 @@ inherit_event(struct perf_event *parent_event, NULL, NULL); if (IS_ERR(child_event)) return child_event; + + if (!atomic_long_inc_not_zero(&parent_event->refcount)) { + free_event(child_event); + return NULL; + } + get_ctx(child_ctx); /* @@ -6844,14 +6856,6 @@ inherit_event(struct perf_event *parent_event, add_event_to_ctx(child_event, child_ctx); raw_spin_unlock_irqrestore(&child_ctx->lock, flags); - /* - * Get a reference to the parent filp - we will fput it - * when the child event exits. This is safe to do because - * we are in the parent and we know that the filp still - * exists and has a nonzero count: - */ - atomic_long_inc(&parent_event->filp->f_count); - /* * Link this into the parent event's child list */ -- cgit v1.2.3 From 500ad2d8b01390c98bc6dce068bccfa9534b8212 Mon Sep 17 00:00:00 2001 From: "K.Prasad" Date: Thu, 2 Aug 2012 13:46:35 +0530 Subject: perf/hwpb: Invoke __perf_event_disable() if interrupts are already disabled While debugging a warning message on PowerPC while using hardware breakpoints, it was discovered that when perf_event_disable is invoked through hw_breakpoint_handler function with interrupts disabled, a subsequent IPI in the code path would trigger a WARN_ON_ONCE message in smp_call_function_single function. This patch calls __perf_event_disable() when interrupts are already disabled, instead of perf_event_disable(). Reported-by: Edjunior Barbosa Machado Signed-off-by: K.Prasad [naveen.n.rao@linux.vnet.ibm.com: v3: Check to make sure we target current task] Signed-off-by: Naveen N. Rao Acked-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20120802081635.5811.17737.stgit@localhost.localdomain [ Fixed build error on MIPS. ] Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 2 ++ kernel/events/core.c | 2 +- kernel/events/hw_breakpoint.c | 11 ++++++++++- 3 files changed, 13 insertions(+), 2 deletions(-) (limited to 'kernel/events/core.c') diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index ad04dfcd6f35..33ed9d605f91 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1296,6 +1296,7 @@ extern int perf_swevent_get_recursion_context(void); extern void perf_swevent_put_recursion_context(int rctx); extern void perf_event_enable(struct perf_event *event); extern void perf_event_disable(struct perf_event *event); +extern int __perf_event_disable(void *info); extern void perf_event_task_tick(void); #else static inline void @@ -1334,6 +1335,7 @@ static inline int perf_swevent_get_recursion_context(void) { return -1; } static inline void perf_swevent_put_recursion_context(int rctx) { } static inline void perf_event_enable(struct perf_event *event) { } static inline void perf_event_disable(struct perf_event *event) { } +static inline int __perf_event_disable(void *info) { return -1; } static inline void perf_event_task_tick(void) { } #endif diff --git a/kernel/events/core.c b/kernel/events/core.c index efef4282b8e8..7fee567153f0 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1253,7 +1253,7 @@ retry: /* * Cross CPU call to disable a performance event */ -static int __perf_event_disable(void *info) +int __perf_event_disable(void *info) { struct perf_event *event = info; struct perf_event_context *ctx = event->ctx; diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c index bb38c4d3ee12..9a7b487c6fe2 100644 --- a/kernel/events/hw_breakpoint.c +++ b/kernel/events/hw_breakpoint.c @@ -453,7 +453,16 @@ int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *att int old_type = bp->attr.bp_type; int err = 0; - perf_event_disable(bp); + /* + * modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it + * will not be possible to raise IPIs that invoke __perf_event_disable. + * So call the function directly after making sure we are targeting the + * current task. + */ + if (irqs_disabled() && bp->ctx && bp->ctx->task == current) + __perf_event_disable(bp); + else + perf_event_disable(bp); bp->attr.bp_addr = attr->bp_addr; bp->attr.bp_type = attr->bp_type; -- cgit v1.2.3