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Groups > linux.kernel > #1606359

[PATCH -v6 06/13] futex: Cleanup refcounting

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Since we're going to add more refcount fiddling, introduce
get_pi_state() to match the existing put_pi_state().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/futex.c |   13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -802,7 +802,7 @@ 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;
 
@@ -812,6 +812,11 @@ static struct futex_pi_state * alloc_pi_
 	return pi_state;
 }
 
+static void get_pi_state(struct futex_pi_state *pi_state)
+{
+	WARN_ON_ONCE(!atomic_inc_not_zero(&pi_state->refcount));
+}
+
 /*
  * Drops a reference to the pi_state object and frees or caches it
  * when the last reference is gone.
@@ -856,7 +861,7 @@ static void put_pi_state(struct futex_pi
  * 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;
 
@@ -1103,7 +1108,7 @@ static int attach_to_pi_state(u32 __user
 		goto out_einval;
 
 out_attach:
-	atomic_inc(&pi_state->refcount);
+	get_pi_state(pi_state);
 	raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
 	*ps = pi_state;
 	return 0;
@@ -1990,7 +1995,7 @@ static int futex_requeue(u32 __user *uad
 			 * refcount on the pi_state and store the pointer in
 			 * the futex_q object of the waiter.
 			 */
-			atomic_inc(&pi_state->refcount);
+			get_pi_state(pi_state);
 			this->pi_state = pi_state;
 			ret = rt_mutex_start_proxy_lock(&pi_state->pi_mutex,
 							this->rt_waiter,

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[PATCH -v6 00/13] The arduous story of FUTEX_UNLOCK_PI Peter Zijlstra <peterz@infradead.org> - 2017-03-22 11:50 +0100
  [PATCH -v6 10/13] futex,rt_mutex: Restructure rt_mutex_finish_proxy_lock() Peter Zijlstra <peterz@infradead.org> - 2017-03-22 11:50 +0100
    [tip:locking/core] futex,rt_mutex: Restructure  rt_mutex_finish_proxy_lock() tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2017-03-23 19:30 +0100
  [PATCH -v6 07/13] futex: Rework inconsistent rt_mutex/futex_q state Peter Zijlstra <peterz@infradead.org> - 2017-03-22 11:50 +0100
    [tip:locking/core] futex: Rework inconsistent rt_mutex/futex_q  state tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2017-03-23 19:30 +0100
  [PATCH -v6 09/13] futex,rt_mutex: Introduce rt_mutex_init_waiter() Peter Zijlstra <peterz@infradead.org> - 2017-03-22 11:50 +0100
    [tip:locking/core] futex,rt_mutex: Introduce rt_mutex_init_waiter() tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2017-03-23 19:30 +0100
  [PATCH -v6 05/13] futex: Change locking rules Peter Zijlstra <peterz@infradead.org> - 2017-03-22 11:50 +0100
    [tip:locking/core] futex: Change locking rules tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2017-03-23 19:30 +0100
  [PATCH -v6 11/13] futex: Rework futex_lock_pi() to use rt_mutex_*_proxy_lock() Peter Zijlstra <peterz@infradead.org> - 2017-03-22 11:50 +0100
    [tip:locking/core] futex: Rework futex_lock_pi() to use  rt_mutex_*_proxy_lock() tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2017-03-23 19:30 +0100
  [PATCH -v6 13/13] futex: futex_lock_pi() vs PREEMPT_RT_FULL Peter Zijlstra <peterz@infradead.org> - 2017-03-22 11:50 +0100
    [tip:locking/core] futex: Drop hb->lock before enqueueing on the  rtmutex tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2017-03-23 19:30 +0100
  [PATCH -v6 03/13] futex: Remove rt_mutex_deadlock_account_*() Peter Zijlstra <peterz@infradead.org> - 2017-03-22 11:50 +0100
    [tip:locking/core] futex: Remove rt_mutex_deadlock_account_*() tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2017-03-23 19:30 +0100
    Re: [PATCH -v6 03/13] futex: Remove rt_mutex_deadlock_account_*() Darren Hart <dvhart@infradead.org> - 2017-03-24 22:30 +0100
      Re: [PATCH -v6 03/13] futex: Remove rt_mutex_deadlock_account_*() Darren Hart <dvhart@infradead.org> - 2017-03-24 22:40 +0100
  [PATCH -v6 12/13] futex: futex_unlock_pi() determinism Peter Zijlstra <peterz@infradead.org> - 2017-03-22 11:50 +0100
    [tip:locking/core] futex: Futex_unlock_pi() determinism tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2017-03-23 19:30 +0100
  [PATCH -v6 06/13] futex: Cleanup refcounting Peter Zijlstra <peterz@infradead.org> - 2017-03-22 11:50 +0100
    [tip:locking/core] futex: Cleanup refcounting tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2017-03-23 19:30 +0100
  [PATCH -v6 04/13] futex,rt_mutex: Provide futex specific rt_mutex API Peter Zijlstra <peterz@infradead.org> - 2017-03-22 11:50 +0100
    [tip:locking/core] futex,rt_mutex: Provide futex specific rt_mutex  API tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2017-03-23 19:30 +0100
    Re: [PATCH -v6 04/13] futex,rt_mutex: Provide futex specific  rt_mutex API Darren Hart <dvhart@infradead.org> - 2017-03-25 01:40 +0100
  [PATCH -v6 02/13] futex: Use smp_store_release() in mark_wake_futex() Peter Zijlstra <peterz@infradead.org> - 2017-03-22 11:50 +0100
    [tip:locking/core] futex: Use smp_store_release() in  mark_wake_futex() tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2017-03-23 19:30 +0100
    Re: [PATCH -v6 02/13] futex: Use smp_store_release() in  mark_wake_futex() Darren Hart <dvhart@infradead.org> - 2017-03-24 22:20 +0100
  Re: [PATCH -v6 00/13] The arduous story of FUTEX_UNLOCK_PI Darren Hart <dvhart@infradead.org> - 2017-03-24 02:50 +0100

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