atomic_inc(&ctx->refcount);
}
+static void free_ctx(struct rcu_head *head)
+{
+ struct perf_counter_context *ctx;
+
+ ctx = container_of(head, struct perf_counter_context, rcu_head);
+ kfree(ctx);
+}
+
static void put_ctx(struct perf_counter_context *ctx)
{
if (atomic_dec_and_test(&ctx->refcount)) {
if (ctx->parent_ctx)
put_ctx(ctx->parent_ctx);
- kfree(ctx);
+ if (ctx->task)
+ put_task_struct(ctx->task);
+ call_rcu(&ctx->rcu_head, free_ctx);
+ }
+}
+
+/*
+ * Get the perf_counter_context for a task and lock it.
+ * This has to cope with with the fact that until it is locked,
+ * the context could get moved to another task.
+ */
+static struct perf_counter_context *perf_lock_task_context(
+ struct task_struct *task, unsigned long *flags)
+{
+ struct perf_counter_context *ctx;
+
+ rcu_read_lock();
+ retry:
+ ctx = rcu_dereference(task->perf_counter_ctxp);
+ if (ctx) {
+ /*
+ * If this context is a clone of another, it might
+ * get swapped for another underneath us by
+ * perf_counter_task_sched_out, though the
+ * rcu_read_lock() protects us from any context
+ * getting freed. Lock the context and check if it
+ * got swapped before we could get the lock, and retry
+ * if so. If we locked the right context, then it
+ * can't get swapped on us any more.
+ */
+ spin_lock_irqsave(&ctx->lock, *flags);
+ if (ctx != rcu_dereference(task->perf_counter_ctxp)) {
+ spin_unlock_irqrestore(&ctx->lock, *flags);
+ goto retry;
+ }
+ }
+ rcu_read_unlock();
+ return ctx;
+}
+
+/*
+ * Get the context for a task and increment its pin_count so it
+ * can't get swapped to another task. This also increments its
+ * reference count so that the context can't get freed.
+ */
+static struct perf_counter_context *perf_pin_task_context(struct task_struct *task)
+{
+ struct perf_counter_context *ctx;
+ unsigned long flags;
+
+ ctx = perf_lock_task_context(task, &flags);
+ if (ctx) {
+ ++ctx->pin_count;
+ get_ctx(ctx);
+ spin_unlock_irqrestore(&ctx->lock, flags);
}
+ return ctx;
+}
+
+static void perf_unpin_context(struct perf_counter_context *ctx)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&ctx->lock, flags);
+ --ctx->pin_count;
+ spin_unlock_irqrestore(&ctx->lock, flags);
+ put_ctx(ctx);
}
/*
}
/*
- * Mark this context as not being a clone of another.
- * Called when counters are added to or removed from this context.
- * We also increment our generation number so that anything that
- * was cloned from this context before this will not match anything
- * cloned from this context after this.
- */
-static void unclone_ctx(struct perf_counter_context *ctx)
-{
- ++ctx->generation;
- if (!ctx->parent_ctx)
- return;
- put_ctx(ctx->parent_ctx);
- ctx->parent_ctx = NULL;
-}
-
-/*
* Cross CPU call to remove a performance counter
*
* We disable the counter on the hardware level first. After that we
struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_counter *counter = info;
struct perf_counter_context *ctx = counter->ctx;
- unsigned long flags;
/*
* If this is a task context, we need to check whether it is
if (ctx->task && cpuctx->task_ctx != ctx)
return;
- spin_lock_irqsave(&ctx->lock, flags);
+ spin_lock(&ctx->lock);
/*
* Protect the list operation against NMI by disabling the
* counters on a global level.
}
perf_enable();
- spin_unlock_irqrestore(&ctx->lock, flags);
+ spin_unlock(&ctx->lock);
}
*
* CPU counters are removed with a smp call. For task counters we only
* call when the task is on a CPU.
+ *
+ * If counter->ctx is a cloned context, callers must make sure that
+ * every task struct that counter->ctx->task could possibly point to
+ * remains valid. This is OK when called from perf_release since
+ * that only calls us on the top-level context, which can't be a clone.
+ * When called from perf_counter_exit_task, it's OK because the
+ * context has been detached from its task.
*/
static void perf_counter_remove_from_context(struct perf_counter *counter)
{
struct perf_counter_context *ctx = counter->ctx;
struct task_struct *task = ctx->task;
- unclone_ctx(ctx);
if (!task) {
/*
* Per cpu counters are removed via an smp call and
struct perf_counter *counter = info;
struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_counter_context *ctx = counter->ctx;
- unsigned long flags;
/*
* If this is a per-task counter, need to check whether this
if (ctx->task && cpuctx->task_ctx != ctx)
return;
- spin_lock_irqsave(&ctx->lock, flags);
+ spin_lock(&ctx->lock);
/*
* If the counter is on, turn it off.
counter->state = PERF_COUNTER_STATE_OFF;
}
- spin_unlock_irqrestore(&ctx->lock, flags);
+ spin_unlock(&ctx->lock);
}
/*
* Disable a counter.
+ *
+ * If counter->ctx is a cloned context, callers must make sure that
+ * every task struct that counter->ctx->task could possibly point to
+ * remains valid. This condition is satisifed when called through
+ * perf_counter_for_each_child or perf_counter_for_each because they
+ * hold the top-level counter's child_mutex, so any descendant that
+ * goes to exit will block in sync_child_counter.
+ * When called from perf_pending_counter it's OK because counter->ctx
+ * is the current context on this CPU and preemption is disabled,
+ * hence we can't get into perf_counter_task_sched_out for this context.
*/
static void perf_counter_disable(struct perf_counter *counter)
{
struct perf_counter_context *ctx = counter->ctx;
struct perf_counter *leader = counter->group_leader;
int cpu = smp_processor_id();
- unsigned long flags;
int err;
/*
cpuctx->task_ctx = ctx;
}
- spin_lock_irqsave(&ctx->lock, flags);
+ spin_lock(&ctx->lock);
ctx->is_active = 1;
update_context_time(ctx);
unlock:
perf_enable();
- spin_unlock_irqrestore(&ctx->lock, flags);
+ spin_unlock(&ctx->lock);
}
/*
struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_counter_context *ctx = counter->ctx;
struct perf_counter *leader = counter->group_leader;
- unsigned long flags;
int err;
/*
cpuctx->task_ctx = ctx;
}
- spin_lock_irqsave(&ctx->lock, flags);
+ spin_lock(&ctx->lock);
ctx->is_active = 1;
update_context_time(ctx);
}
unlock:
- spin_unlock_irqrestore(&ctx->lock, flags);
+ spin_unlock(&ctx->lock);
}
/*
* Enable a counter.
+ *
+ * If counter->ctx is a cloned context, callers must make sure that
+ * every task struct that counter->ctx->task could possibly point to
+ * remains valid. This condition is satisfied when called through
+ * perf_counter_for_each_child or perf_counter_for_each as described
+ * for perf_counter_disable.
*/
static void perf_counter_enable(struct perf_counter *counter)
{
struct perf_counter_context *ctx2)
{
return ctx1->parent_ctx && ctx1->parent_ctx == ctx2->parent_ctx
- && ctx1->parent_gen == ctx2->parent_gen;
+ && ctx1->parent_gen == ctx2->parent_gen
+ && !ctx1->pin_count && !ctx2->pin_count;
}
/*
struct perf_cpu_context *cpuctx = &per_cpu(perf_cpu_context, cpu);
struct perf_counter_context *ctx = task->perf_counter_ctxp;
struct perf_counter_context *next_ctx;
+ struct perf_counter_context *parent;
struct pt_regs *regs;
+ int do_switch = 1;
regs = task_pt_regs(task);
perf_swcounter_event(PERF_COUNT_CONTEXT_SWITCHES, 1, 1, regs, 0);
return;
update_context_time(ctx);
+
+ rcu_read_lock();
+ parent = rcu_dereference(ctx->parent_ctx);
next_ctx = next->perf_counter_ctxp;
- if (next_ctx && context_equiv(ctx, next_ctx)) {
- task->perf_counter_ctxp = next_ctx;
- next->perf_counter_ctxp = ctx;
- ctx->task = next;
- next_ctx->task = task;
- return;
+ if (parent && next_ctx &&
+ rcu_dereference(next_ctx->parent_ctx) == parent) {
+ /*
+ * Looks like the two contexts are clones, so we might be
+ * able to optimize the context switch. We lock both
+ * contexts and check that they are clones under the
+ * lock (including re-checking that neither has been
+ * uncloned in the meantime). It doesn't matter which
+ * order we take the locks because no other cpu could
+ * be trying to lock both of these tasks.
+ */
+ spin_lock(&ctx->lock);
+ spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
+ if (context_equiv(ctx, next_ctx)) {
+ /*
+ * XXX do we need a memory barrier of sorts
+ * wrt to rcu_dereference() of perf_counter_ctxp
+ */
+ task->perf_counter_ctxp = next_ctx;
+ next->perf_counter_ctxp = ctx;
+ ctx->task = next;
+ next_ctx->task = task;
+ do_switch = 0;
+ }
+ spin_unlock(&next_ctx->lock);
+ spin_unlock(&ctx->lock);
}
+ rcu_read_unlock();
- __perf_counter_sched_out(ctx, cpuctx);
-
- cpuctx->task_ctx = NULL;
+ if (do_switch) {
+ __perf_counter_sched_out(ctx, cpuctx);
+ cpuctx->task_ctx = NULL;
+ }
}
+/*
+ * Called with IRQs disabled
+ */
static void __perf_counter_task_sched_out(struct perf_counter_context *ctx)
{
struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
if (!cpuctx->task_ctx)
return;
+
+ if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
+ return;
+
__perf_counter_sched_out(ctx, cpuctx);
cpuctx->task_ctx = NULL;
}
+/*
+ * Called with IRQs disabled
+ */
static void perf_counter_cpu_sched_out(struct perf_cpu_context *cpuctx)
{
__perf_counter_sched_out(&cpuctx->ctx, cpuctx);
ctx->task = task;
}
-static void put_context(struct perf_counter_context *ctx)
-{
- if (ctx->task)
- put_task_struct(ctx->task);
-}
-
static struct perf_counter_context *find_get_context(pid_t pid, int cpu)
{
struct perf_cpu_context *cpuctx;
struct perf_counter_context *ctx;
- struct perf_counter_context *tctx;
+ struct perf_counter_context *parent_ctx;
struct task_struct *task;
+ unsigned long flags;
+ int err;
/*
* If cpu is not a wildcard then this is a percpu counter:
cpuctx = &per_cpu(perf_cpu_context, cpu);
ctx = &cpuctx->ctx;
+ get_ctx(ctx);
return ctx;
}
if (!task)
return ERR_PTR(-ESRCH);
+ /*
+ * Can't attach counters to a dying task.
+ */
+ err = -ESRCH;
+ if (task->flags & PF_EXITING)
+ goto errout;
+
/* Reuse ptrace permission checks for now. */
- if (!ptrace_may_access(task, PTRACE_MODE_READ)) {
- put_task_struct(task);
- return ERR_PTR(-EACCES);
+ err = -EACCES;
+ if (!ptrace_may_access(task, PTRACE_MODE_READ))
+ goto errout;
+
+ retry:
+ ctx = perf_lock_task_context(task, &flags);
+ if (ctx) {
+ parent_ctx = ctx->parent_ctx;
+ if (parent_ctx) {
+ put_ctx(parent_ctx);
+ ctx->parent_ctx = NULL; /* no longer a clone */
+ }
+ /*
+ * Get an extra reference before dropping the lock so that
+ * this context won't get freed if the task exits.
+ */
+ get_ctx(ctx);
+ spin_unlock_irqrestore(&ctx->lock, flags);
}
- ctx = task->perf_counter_ctxp;
if (!ctx) {
ctx = kmalloc(sizeof(struct perf_counter_context), GFP_KERNEL);
- if (!ctx) {
- put_task_struct(task);
- return ERR_PTR(-ENOMEM);
- }
+ err = -ENOMEM;
+ if (!ctx)
+ goto errout;
__perf_counter_init_context(ctx, task);
- /*
- * Make sure other cpus see correct values for *ctx
- * once task->perf_counter_ctxp is visible to them.
- */
- smp_wmb();
- tctx = cmpxchg(&task->perf_counter_ctxp, NULL, ctx);
- if (tctx) {
+ get_ctx(ctx);
+ if (cmpxchg(&task->perf_counter_ctxp, NULL, ctx)) {
/*
* We raced with some other task; use
* the context they set.
*/
kfree(ctx);
- ctx = tctx;
+ goto retry;
}
+ get_task_struct(task);
}
+ put_task_struct(task);
return ctx;
+
+ errout:
+ put_task_struct(task);
+ return ERR_PTR(err);
}
static void free_counter_rcu(struct rcu_head *head)
struct perf_counter *counter;
counter = container_of(head, struct perf_counter, rcu_head);
- put_ctx(counter->ctx);
kfree(counter);
}
if (counter->destroy)
counter->destroy(counter);
+ put_ctx(counter->ctx);
call_rcu(&counter->rcu_head, free_counter_rcu);
}
file->private_data = NULL;
+ WARN_ON_ONCE(ctx->parent_ctx);
mutex_lock(&ctx->mutex);
perf_counter_remove_from_context(counter);
mutex_unlock(&ctx->mutex);
put_task_struct(counter->owner);
free_counter(counter);
- put_context(ctx);
return 0;
}
if (counter->state == PERF_COUNTER_STATE_ERROR)
return 0;
+ WARN_ON_ONCE(counter->ctx->parent_ctx);
mutex_lock(&counter->child_mutex);
values[0] = perf_counter_read(counter);
n = 1;
struct perf_counter_context *ctx = counter->ctx;
struct perf_counter *sibling;
+ WARN_ON_ONCE(ctx->parent_ctx);
mutex_lock(&ctx->mutex);
counter = counter->group_leader;
mutex_unlock(&ctx->mutex);
}
+/*
+ * Holding the top-level counter's child_mutex means that any
+ * descendant process that has inherited this counter will block
+ * in sync_child_counter if it goes to exit, thus satisfying the
+ * task existence requirements of perf_counter_enable/disable.
+ */
static void perf_counter_for_each_child(struct perf_counter *counter,
void (*func)(struct perf_counter *))
{
struct perf_counter *child;
+ WARN_ON_ONCE(counter->ctx->parent_ctx);
mutex_lock(&counter->child_mutex);
func(counter);
list_for_each_entry(child, &counter->child_list, child_list)
{
struct perf_counter *child;
+ WARN_ON_ONCE(counter->ctx->parent_ctx);
mutex_lock(&counter->child_mutex);
perf_counter_for_each_sibling(counter, func);
list_for_each_entry(child, &counter->child_list, child_list)
{
struct perf_counter *counter = vma->vm_file->private_data;
+ WARN_ON_ONCE(counter->ctx->parent_ctx);
if (atomic_dec_and_mutex_lock(&counter->mmap_count,
&counter->mmap_mutex)) {
struct user_struct *user = current_user();
if (vma->vm_pgoff != 0)
return -EINVAL;
+ WARN_ON_ONCE(counter->ctx->parent_ctx);
mutex_lock(&counter->mmap_mutex);
if (atomic_inc_not_zero(&counter->mmap_count)) {
if (nr_pages != counter->data->nr_pages)
static void perf_counter_comm_event(struct perf_comm_event *comm_event)
{
struct perf_cpu_context *cpuctx;
+ struct perf_counter_context *ctx;
unsigned int size;
char *comm = comm_event->task->comm;
perf_counter_comm_ctx(&cpuctx->ctx, comm_event);
put_cpu_var(perf_cpu_context);
- perf_counter_comm_ctx(current->perf_counter_ctxp, comm_event);
+ rcu_read_lock();
+ /*
+ * doesn't really matter which of the child contexts the
+ * events ends up in.
+ */
+ ctx = rcu_dereference(current->perf_counter_ctxp);
+ if (ctx)
+ perf_counter_comm_ctx(ctx, comm_event);
+ rcu_read_unlock();
}
void perf_counter_comm(struct task_struct *task)
if (!atomic_read(&nr_comm_tracking))
return;
- if (!current->perf_counter_ctxp)
- return;
comm_event = (struct perf_comm_event){
.task = task,
static void perf_counter_mmap_event(struct perf_mmap_event *mmap_event)
{
struct perf_cpu_context *cpuctx;
+ struct perf_counter_context *ctx;
struct file *file = mmap_event->file;
unsigned int size;
char tmp[16];
perf_counter_mmap_ctx(&cpuctx->ctx, mmap_event);
put_cpu_var(perf_cpu_context);
- perf_counter_mmap_ctx(current->perf_counter_ctxp, mmap_event);
+ rcu_read_lock();
+ /*
+ * doesn't really matter which of the child contexts the
+ * events ends up in.
+ */
+ ctx = rcu_dereference(current->perf_counter_ctxp);
+ if (ctx)
+ perf_counter_mmap_ctx(ctx, mmap_event);
+ rcu_read_unlock();
kfree(buf);
}
if (!atomic_read(&nr_mmap_tracking))
return;
- if (!current->perf_counter_ctxp)
- return;
mmap_event = (struct perf_mmap_event){
.file = file,
.time = sched_clock(),
};
- ret = perf_output_begin(&handle, counter, sizeof(throttle_event), 0, 0);
+ ret = perf_output_begin(&handle, counter, sizeof(throttle_event), 1, 0);
if (ret)
return;
{
struct perf_cpu_context *cpuctx = &get_cpu_var(perf_cpu_context);
int *recursion = perf_swcounter_recursion_context(cpuctx);
+ struct perf_counter_context *ctx;
if (*recursion)
goto out;
perf_swcounter_ctx_event(&cpuctx->ctx, type, event,
nr, nmi, regs, addr);
- if (cpuctx->task_ctx) {
- perf_swcounter_ctx_event(cpuctx->task_ctx, type, event,
- nr, nmi, regs, addr);
- }
+ rcu_read_lock();
+ /*
+ * doesn't really matter which of the child contexts the
+ * events ends up in.
+ */
+ ctx = rcu_dereference(current->perf_counter_ctxp);
+ if (ctx)
+ perf_swcounter_ctx_event(ctx, type, event, nr, nmi, regs, addr);
+ rcu_read_unlock();
barrier();
(*recursion)--;
counter->group_leader = group_leader;
counter->pmu = NULL;
counter->ctx = ctx;
- get_ctx(ctx);
+ counter->oncpu = -1;
counter->state = PERF_COUNTER_STATE_INACTIVE;
if (hw_event->disabled)
goto err_free_put_context;
counter->filp = counter_file;
+ WARN_ON_ONCE(ctx->parent_ctx);
mutex_lock(&ctx->mutex);
perf_install_in_context(ctx, counter, cpu);
+ ++ctx->generation;
mutex_unlock(&ctx->mutex);
counter->owner = current;
kfree(counter);
err_put_context:
- put_context(ctx);
+ put_ctx(ctx);
goto out_fput;
}
group_leader, GFP_KERNEL);
if (IS_ERR(child_counter))
return child_counter;
+ get_ctx(child_ctx);
/*
* Make the child state follow the state of the parent counter,
/*
* Link this into the parent counter's child list
*/
+ WARN_ON_ONCE(parent_counter->ctx->parent_ctx);
mutex_lock(&parent_counter->child_mutex);
list_add_tail(&child_counter->child_list, &parent_counter->child_list);
mutex_unlock(&parent_counter->child_mutex);
/*
* Remove this counter from the parent's list
*/
+ WARN_ON_ONCE(parent_counter->ctx->parent_ctx);
mutex_lock(&parent_counter->child_mutex);
list_del_init(&child_counter->child_list);
mutex_unlock(&parent_counter->child_mutex);
}
static void
-__perf_counter_exit_task(struct task_struct *child,
- struct perf_counter *child_counter,
+__perf_counter_exit_task(struct perf_counter *child_counter,
struct perf_counter_context *child_ctx)
{
struct perf_counter *parent_counter;
/*
* When a child task exits, feed back counter values to parent counters.
- *
- * Note: we may be running in child context, but the PID is not hashed
- * anymore so new counters will not be added.
- * (XXX not sure that is true when we get called from flush_old_exec.
- * -- paulus)
*/
void perf_counter_exit_task(struct task_struct *child)
{
struct perf_counter_context *child_ctx;
unsigned long flags;
- WARN_ON_ONCE(child != current);
-
- child_ctx = child->perf_counter_ctxp;
-
- if (likely(!child_ctx))
+ if (likely(!child->perf_counter_ctxp))
return;
local_irq_save(flags);
+ /*
+ * We can't reschedule here because interrupts are disabled,
+ * and either child is current or it is a task that can't be
+ * scheduled, so we are now safe from rescheduling changing
+ * our context.
+ */
+ child_ctx = child->perf_counter_ctxp;
__perf_counter_task_sched_out(child_ctx);
+
+ /*
+ * Take the context lock here so that if find_get_context is
+ * reading child->perf_counter_ctxp, we wait until it has
+ * incremented the context's refcount before we do put_ctx below.
+ */
+ spin_lock(&child_ctx->lock);
child->perf_counter_ctxp = NULL;
+ if (child_ctx->parent_ctx) {
+ /*
+ * This context is a clone; unclone it so it can't get
+ * swapped to another process while we're removing all
+ * the counters from it.
+ */
+ put_ctx(child_ctx->parent_ctx);
+ child_ctx->parent_ctx = NULL;
+ }
+ spin_unlock(&child_ctx->lock);
local_irq_restore(flags);
mutex_lock(&child_ctx->mutex);
again:
list_for_each_entry_safe(child_counter, tmp, &child_ctx->counter_list,
list_entry)
- __perf_counter_exit_task(child, child_counter, child_ctx);
+ __perf_counter_exit_task(child_counter, child_ctx);
/*
* If the last counter was a group counter, it will have appended all
}
/*
+ * free an unexposed, unused context as created by inheritance by
+ * init_task below, used by fork() in case of fail.
+ */
+void perf_counter_free_task(struct task_struct *task)
+{
+ struct perf_counter_context *ctx = task->perf_counter_ctxp;
+ struct perf_counter *counter, *tmp;
+
+ if (!ctx)
+ return;
+
+ mutex_lock(&ctx->mutex);
+again:
+ list_for_each_entry_safe(counter, tmp, &ctx->counter_list, list_entry) {
+ struct perf_counter *parent = counter->parent;
+
+ if (WARN_ON_ONCE(!parent))
+ continue;
+
+ mutex_lock(&parent->child_mutex);
+ list_del_init(&counter->child_list);
+ mutex_unlock(&parent->child_mutex);
+
+ fput(parent->filp);
+
+ list_del_counter(counter, ctx);
+ free_counter(counter);
+ }
+
+ if (!list_empty(&ctx->counter_list))
+ goto again;
+
+ mutex_unlock(&ctx->mutex);
+
+ put_ctx(ctx);
+}
+
+/*
* Initialize the perf_counter context in task_struct
*/
int perf_counter_init_task(struct task_struct *child)
{
struct perf_counter_context *child_ctx, *parent_ctx;
+ struct perf_counter_context *cloned_ctx;
struct perf_counter *counter;
struct task_struct *parent = current;
int inherited_all = 1;
mutex_init(&child->perf_counter_mutex);
INIT_LIST_HEAD(&child->perf_counter_list);
- parent_ctx = parent->perf_counter_ctxp;
- if (likely(!parent_ctx || !parent_ctx->nr_counters))
+ if (likely(!parent->perf_counter_ctxp))
return 0;
/*
__perf_counter_init_context(child_ctx, child);
child->perf_counter_ctxp = child_ctx;
+ get_task_struct(child);
+
+ /*
+ * If the parent's context is a clone, pin it so it won't get
+ * swapped under us.
+ */
+ parent_ctx = perf_pin_task_context(parent);
+
+ /*
+ * No need to check if parent_ctx != NULL here; since we saw
+ * it non-NULL earlier, the only reason for it to become NULL
+ * is if we exit, and since we're currently in the middle of
+ * a fork we can't be exiting at the same time.
+ */
/*
* Lock the parent list. No need to lock the child - not PID
/*
* Mark the child context as a clone of the parent
* context, or of whatever the parent is a clone of.
+ * Note that if the parent is a clone, it could get
+ * uncloned at any point, but that doesn't matter
+ * because the list of counters and the generation
+ * count can't have changed since we took the mutex.
*/
- if (parent_ctx->parent_ctx) {
- child_ctx->parent_ctx = parent_ctx->parent_ctx;
+ cloned_ctx = rcu_dereference(parent_ctx->parent_ctx);
+ if (cloned_ctx) {
+ child_ctx->parent_ctx = cloned_ctx;
child_ctx->parent_gen = parent_ctx->parent_gen;
} else {
child_ctx->parent_ctx = parent_ctx;
mutex_unlock(&parent_ctx->mutex);
+ perf_unpin_context(parent_ctx);
+
return ret;
}
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff