perf_counter: Sanitize counter->mutex

s/counter->mutex/counter->child_mutex/ and make sure its only
used to protect child_list.

The usage in __perf_counter_exit_task() doesn't appear to be
problematic since ctx->mutex also covers anything related to fd
tear-down.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <20090523163012.533186528@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 23ddd29..4ab8050 100644 (file)
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -452,9 +452,6 @@ struct perf_counter {
        struct perf_counter_context     *ctx;
        struct file                     *filp;
 
-       struct perf_counter             *parent;
-       struct list_head                child_list;
-
        /*
         * These accumulate total time (in nanoseconds) that children
         * counters have been enabled and running, respectively.
@@ -465,7 +462,9 @@ struct perf_counter {
        /*
         * Protect attach/detach and child_list:
         */
-       struct mutex                    mutex;
+       struct mutex                    child_mutex;
+       struct list_head                child_list;
+       struct perf_counter             *parent;
 
        int                             oncpu;
        int                             cpu;

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 2f410ea..679c3b5 100644 (file)
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -111,6 +111,10 @@ static void put_ctx(struct perf_counter_context *ctx)
        }
 }
 
+/*
+ * Add a counter from the lists for its context.
+ * Must be called with ctx->mutex and ctx->lock held.
+ */
 static void
 list_add_counter(struct perf_counter *counter, struct perf_counter_context *ctx)
 {
@@ -136,7 +140,7 @@ list_add_counter(struct perf_counter *counter, struct perf_counter_context *ctx)
 
 /*
  * Remove a counter from the lists for its context.
- * Must be called with counter->mutex and ctx->mutex held.
+ * Must be called with ctx->mutex and ctx->lock held.
  */
 static void
 list_del_counter(struct perf_counter *counter, struct perf_counter_context *ctx)
@@ -276,7 +280,7 @@ static void __perf_counter_remove_from_context(void *info)
 /*
  * Remove the counter from a task's (or a CPU's) list of counters.
  *
- * Must be called with counter->mutex and ctx->mutex held.
+ * Must be called with ctx->mutex held.
  *
  * CPU counters are removed with a smp call. For task counters we only
  * call when the task is on a CPU.
@@ -1407,11 +1411,7 @@ static int perf_release(struct inode *inode, struct file *file)
        file->private_data = NULL;
 
        mutex_lock(&ctx->mutex);
-       mutex_lock(&counter->mutex);
-
        perf_counter_remove_from_context(counter);
-
-       mutex_unlock(&counter->mutex);
        mutex_unlock(&ctx->mutex);
 
        free_counter(counter);
@@ -1437,7 +1437,7 @@ perf_read_hw(struct perf_counter *counter, char __user *buf, size_t count)
        if (counter->state == PERF_COUNTER_STATE_ERROR)
                return 0;
 
-       mutex_lock(&counter->mutex);
+       mutex_lock(&counter->child_mutex);
        values[0] = perf_counter_read(counter);
        n = 1;
        if (counter->hw_event.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
@@ -1446,7 +1446,7 @@ perf_read_hw(struct perf_counter *counter, char __user *buf, size_t count)
        if (counter->hw_event.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
                values[n++] = counter->total_time_running +
                        atomic64_read(&counter->child_total_time_running);
-       mutex_unlock(&counter->mutex);
+       mutex_unlock(&counter->child_mutex);
 
        if (count < n * sizeof(u64))
                return -EINVAL;
@@ -1510,11 +1510,11 @@ static void perf_counter_for_each_child(struct perf_counter *counter,
 {
        struct perf_counter *child;
 
-       mutex_lock(&counter->mutex);
+       mutex_lock(&counter->child_mutex);
        func(counter);
        list_for_each_entry(child, &counter->child_list, child_list)
                func(child);
-       mutex_unlock(&counter->mutex);
+       mutex_unlock(&counter->child_mutex);
 }
 
 static void perf_counter_for_each(struct perf_counter *counter,
@@ -1522,11 +1522,11 @@ static void perf_counter_for_each(struct perf_counter *counter,
 {
        struct perf_counter *child;
 
-       mutex_lock(&counter->mutex);
+       mutex_lock(&counter->child_mutex);
        perf_counter_for_each_sibling(counter, func);
        list_for_each_entry(child, &counter->child_list, child_list)
                perf_counter_for_each_sibling(child, func);
-       mutex_unlock(&counter->mutex);
+       mutex_unlock(&counter->child_mutex);
 }
 
 static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
@@ -3106,7 +3106,9 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
        if (!group_leader)
                group_leader = counter;
 
-       mutex_init(&counter->mutex);
+       mutex_init(&counter->child_mutex);
+       INIT_LIST_HEAD(&counter->child_list);
+
        INIT_LIST_HEAD(&counter->list_entry);
        INIT_LIST_HEAD(&counter->event_entry);
        INIT_LIST_HEAD(&counter->sibling_list);
@@ -3114,8 +3116,6 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
 
        mutex_init(&counter->mmap_mutex);
 
-       INIT_LIST_HEAD(&counter->child_list);
-
        counter->cpu                    = cpu;
        counter->hw_event               = *hw_event;
        counter->group_leader           = group_leader;
@@ -3346,10 +3346,9 @@ inherit_counter(struct perf_counter *parent_counter,
        /*
         * Link this into the parent counter's child list
         */
-       mutex_lock(&parent_counter->mutex);
+       mutex_lock(&parent_counter->child_mutex);
        list_add_tail(&child_counter->child_list, &parent_counter->child_list);
-
-       mutex_unlock(&parent_counter->mutex);
+       mutex_unlock(&parent_counter->child_mutex);
 
        return child_counter;
 }
@@ -3396,9 +3395,9 @@ static void sync_child_counter(struct perf_counter *child_counter,
        /*
         * Remove this counter from the parent's list
         */
-       mutex_lock(&parent_counter->mutex);
+       mutex_lock(&parent_counter->child_mutex);
        list_del_init(&child_counter->child_list);
-       mutex_unlock(&parent_counter->mutex);
+       mutex_unlock(&parent_counter->child_mutex);
 
        /*
         * Release the parent counter, if this was the last
@@ -3414,17 +3413,9 @@ __perf_counter_exit_task(struct task_struct *child,
 {
        struct perf_counter *parent_counter;
 
-       /*
-        * Protect against concurrent operations on child_counter
-        * due its fd getting closed, etc.
-        */
-       mutex_lock(&child_counter->mutex);
-
        update_counter_times(child_counter);
        list_del_counter(child_counter, child_ctx);
 
-       mutex_unlock(&child_counter->mutex);
-
        parent_counter = child_counter->parent;
        /*
         * It can happen that parent exits first, and has counters