[PATCH 07/17] futex: Cleanup refcounting
From: Peter Zijlstra
commit bf92cf3a5100f5a0d5f9834787b130159397cb22 upstream.
Add a put_pit_state() as counterpart for get_pi_state() so the refcounting
becomes consistent.
Signed-off-by: Peter Zijlstra (Intel)
Cc: juri.le...@arm.com
Cc: bige...@linutronix.de
Cc: xlp...@redhat.com
Cc: rost...@goodmis.org
Cc: mathieu.desnoy...@efficios.com
Cc: jdesfos...@efficios.com
Cc: dvh...@infradead.org
Cc: bris...@redhat.com
Link: http://lkml.kernel.org/r/20170322104151.801778...@infradead.org
Signed-off-by: Thomas Gleixner
Conflicts:
kernel/futex.c
Tested-by:Henrik Austad
---
kernel/futex.c | 19 ++-
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index 52e3678..9d7d462 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -799,7 +799,7 @@ static int refill_pi_state_cache(void)
return 0;
}
-static struct futex_pi_state * alloc_pi_state(void)
+static struct futex_pi_state *alloc_pi_state(void)
{
struct futex_pi_state *pi_state = current->pi_state_cache;
@@ -809,6 +809,11 @@ static struct futex_pi_state * alloc_pi_state(void)
return pi_state;
}
+static void get_pi_state(struct futex_pi_state *pi_state)
+{
+ WARN_ON_ONCE(!atomic_inc_not_zero(_state->refcount));
+}
+
/*
* Must be called with the hb lock held.
*/
@@ -850,7 +855,7 @@ static void free_pi_state(struct futex_pi_state *pi_state)
* Look up the task based on what TID userspace gave us.
* We dont trust it.
*/
-static struct task_struct * futex_find_get_task(pid_t pid)
+static struct task_struct *futex_find_get_task(pid_t pid)
{
struct task_struct *p;
@@ -1097,7 +1102,7 @@ static int attach_to_pi_state(u32 __user *uaddr, u32 uval,
goto out_einval;
out_attach:
- atomic_inc(_state->refcount);
+ get_pi_state(pi_state);
raw_spin_unlock_irq(_state->pi_mutex.wait_lock);
*ps = pi_state;
return 0;
@@ -2019,8 +2024,12 @@ retry_private:
* of requeue_pi if we couldn't acquire the lock atomically.
*/
if (requeue_pi) {
- /* Prepare the waiter to take the rt_mutex. */
- atomic_inc(_state->refcount);
+ /*
+* Prepare the waiter to take the rt_mutex. Take a
+* refcount on the pi_state and store the pointer in
+* the futex_q object of the waiter.
+*/
+ get_pi_state(pi_state);
this->pi_state = pi_state;
ret = rt_mutex_start_proxy_lock(_state->pi_mutex,
this->rt_waiter,
--
2.7.4
[PATCH 07/17] futex: Cleanup refcounting
From: Peter Zijlstra
commit bf92cf3a5100f5a0d5f9834787b130159397cb22 upstream.
Add a put_pit_state() as counterpart for get_pi_state() so the refcounting
becomes consistent.
Signed-off-by: Peter Zijlstra (Intel)
Cc: juri.le...@arm.com
Cc: bige...@linutronix.de
Cc: xlp...@redhat.com
Cc: rost...@goodmis.org
Cc: mathieu.desnoy...@efficios.com
Cc: jdesfos...@efficios.com
Cc: dvh...@infradead.org
Cc: bris...@redhat.com
Link: http://lkml.kernel.org/r/20170322104151.801778...@infradead.org
Signed-off-by: Thomas Gleixner
Conflicts:
kernel/futex.c
Tested-by:Henrik Austad
---
kernel/futex.c | 19 ++-
1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index 52e3678..9d7d462 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -799,7 +799,7 @@ static int refill_pi_state_cache(void)
return 0;
}
-static struct futex_pi_state * alloc_pi_state(void)
+static struct futex_pi_state *alloc_pi_state(void)
{
struct futex_pi_state *pi_state = current->pi_state_cache;
@@ -809,6 +809,11 @@ static struct futex_pi_state * alloc_pi_state(void)
return pi_state;
}
+static void get_pi_state(struct futex_pi_state *pi_state)
+{
+ WARN_ON_ONCE(!atomic_inc_not_zero(_state->refcount));
+}
+
/*
* Must be called with the hb lock held.
*/
@@ -850,7 +855,7 @@ static void free_pi_state(struct futex_pi_state *pi_state)
* Look up the task based on what TID userspace gave us.
* We dont trust it.
*/
-static struct task_struct * futex_find_get_task(pid_t pid)
+static struct task_struct *futex_find_get_task(pid_t pid)
{
struct task_struct *p;
@@ -1097,7 +1102,7 @@ static int attach_to_pi_state(u32 __user *uaddr, u32 uval,
goto out_einval;
out_attach:
- atomic_inc(_state->refcount);
+ get_pi_state(pi_state);
raw_spin_unlock_irq(_state->pi_mutex.wait_lock);
*ps = pi_state;
return 0;
@@ -2019,8 +2024,12 @@ retry_private:
* of requeue_pi if we couldn't acquire the lock atomically.
*/
if (requeue_pi) {
- /* Prepare the waiter to take the rt_mutex. */
- atomic_inc(_state->refcount);
+ /*
+* Prepare the waiter to take the rt_mutex. Take a
+* refcount on the pi_state and store the pointer in
+* the futex_q object of the waiter.
+*/
+ get_pi_state(pi_state);
this->pi_state = pi_state;
ret = rt_mutex_start_proxy_lock(_state->pi_mutex,
this->rt_waiter,
--
2.7.4
