forked from rrcarlosr/Jetpack
66 lines
2.2 KiB
Diff
66 lines
2.2 KiB
Diff
From a8349a2cd1e0545800c8fe0899a78914a41ce582 Mon Sep 17 00:00:00 2001
|
|
From: Thomas Gleixner <tglx@linutronix.de>
|
|
Date: Wed, 8 Mar 2017 14:23:35 +0100
|
|
Subject: [PATCH 078/352] futex: workaround migrate_disable/enable in different
|
|
context
|
|
|
|
migrate_disable()/migrate_enable() takes a different path in atomic() vs
|
|
!atomic() context. These little hacks ensure that we don't underflow / overflow
|
|
the migrate code counts properly while we lock the hb lockwith interrupts
|
|
enabled and unlock it with interrupts disabled.
|
|
|
|
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
|
|
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
|
|
---
|
|
kernel/futex.c | 20 ++++++++++++++++++++
|
|
1 file changed, 20 insertions(+)
|
|
|
|
diff --git a/kernel/futex.c b/kernel/futex.c
|
|
index 239d5ea..7431ff3 100644
|
|
--- a/kernel/futex.c
|
|
+++ b/kernel/futex.c
|
|
@@ -2720,9 +2720,18 @@ static int futex_lock_pi(u32 __user *uaddr, unsigned int flags,
|
|
* lock handoff sequence.
|
|
*/
|
|
raw_spin_lock_irq(&q.pi_state->pi_mutex.wait_lock);
|
|
+ /*
|
|
+ * the migrate_disable() here disables migration in the in_atomic() fast
|
|
+ * path which is enabled again in the following spin_unlock(). We have
|
|
+ * one migrate_disable() pending in the slow-path which is reversed
|
|
+ * after the raw_spin_unlock_irq() where we leave the atomic context.
|
|
+ */
|
|
+ migrate_disable();
|
|
+
|
|
spin_unlock(q.lock_ptr);
|
|
ret = __rt_mutex_start_proxy_lock(&q.pi_state->pi_mutex, &rt_waiter, current);
|
|
raw_spin_unlock_irq(&q.pi_state->pi_mutex.wait_lock);
|
|
+ migrate_enable();
|
|
|
|
if (ret) {
|
|
if (ret == 1)
|
|
@@ -2866,10 +2875,21 @@ static int futex_unlock_pi(u32 __user *uaddr, unsigned int flags)
|
|
* observed.
|
|
*/
|
|
raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
|
|
+ /*
|
|
+ * Magic trickery for now to make the RT migrate disable
|
|
+ * logic happy. The following spin_unlock() happens with
|
|
+ * interrupts disabled so the internal migrate_enable()
|
|
+ * won't undo the migrate_disable() which was issued when
|
|
+ * locking hb->lock.
|
|
+ */
|
|
+ migrate_disable();
|
|
spin_unlock(&hb->lock);
|
|
|
|
+ /* Drops pi_state->pi_mutex.wait_lock */
|
|
ret = wake_futex_pi(uaddr, uval, pi_state);
|
|
|
|
+ migrate_enable();
|
|
+
|
|
put_pi_state(pi_state);
|
|
|
|
/*
|
|
--
|
|
2.7.4
|
|
|