From 39f710e222c6e981f751df63b84ecb82b67940d0 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 22 Mar 2017 11:35:53 +0100 Subject: [PATCH 010/365] futex: Cleanup refcounting Upstream commit bf92cf3a5100f5a0d5f9834787b130159397cb22 Add a put_pit_state() as counterpart for get_pi_state() so the refcounting becomes consistent. Signed-off-by: Peter Zijlstra (Intel) Cc: juri.lelli@arm.com Cc: bigeasy@linutronix.de Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: dvhart@infradead.org Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170322104151.801778516@infradead.org Signed-off-by: Thomas Gleixner Signed-off-by: Sebastian Andrzej Siewior --- kernel/futex.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index c0d5e64b37b2..629db2cd530e 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -818,7 +818,7 @@ 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; @@ -828,6 +828,11 @@ 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(&pi_state->refcount)); +} + /* * Drops a reference to the pi_state object and frees or caches it * when the last reference is gone. @@ -872,7 +877,7 @@ static void put_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; @@ -1119,7 +1124,7 @@ static int attach_to_pi_state(u32 __user *uaddr, u32 uval, 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; @@ -2056,7 +2061,7 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags, * 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, -- 2.28.0