Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Ingo Molnar:
"Misc fixes:
pvqspinlocks:
- an instrumentation fix
futexes:
- preempt-count vs pagefault_disable decouple corner case fix
- futex requeue plist race window fix
- futex UNLOCK_PI transaction fix for a corner case"
* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
asm-generic/futex: Re-enable preemption in futex_atomic_cmpxchg_inatomic()
futex: Acknowledge a new waiter in counter before plist
futex: Handle unlock_pi race gracefully
locking/pvqspinlock: Fix division by zero in qstat_read()
+34
-9
+6
-2
include/asm-generic/futex.h
+6
-2
include/asm-generic/futex.h
···
108
108
u32 val;
109
109
110
110
preempt_disable();
111
-
if (unlikely(get_user(val, uaddr) != 0))
111
+
if (unlikely(get_user(val, uaddr) != 0)) {
112
+
preempt_enable();
112
113
return -EFAULT;
114
+
}
113
115
114
-
if (val == oldval && unlikely(put_user(newval, uaddr) != 0))
116
+
if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) {
117
+
preempt_enable();
115
118
return -EFAULT;
119
+
}
116
120
117
121
*uval = val;
118
122
preempt_enable();
+23
-4
kernel/futex.c
+23
-4
kernel/futex.c
···
1295
1295
if (unlikely(should_fail_futex(true)))
1296
1296
ret = -EFAULT;
1297
1297
1298
-
if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))
1298
+
if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) {
1299
1299
ret = -EFAULT;
1300
-
else if (curval != uval)
1301
-
ret = -EINVAL;
1300
+
} else if (curval != uval) {
1301
+
/*
1302
+
* If a unconditional UNLOCK_PI operation (user space did not
1303
+
* try the TID->0 transition) raced with a waiter setting the
1304
+
* FUTEX_WAITERS flag between get_user() and locking the hash
1305
+
* bucket lock, retry the operation.
1306
+
*/
1307
+
if ((FUTEX_TID_MASK & curval) == uval)
1308
+
ret = -EAGAIN;
1309
+
else
1310
+
ret = -EINVAL;
1311
+
}
1302
1312
if (ret) {
1303
1313
raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
1304
1314
return ret;
···
1535
1525
if (likely(&hb1->chain != &hb2->chain)) {
1536
1526
plist_del(&q->list, &hb1->chain);
1537
1527
hb_waiters_dec(hb1);
1538
-
plist_add(&q->list, &hb2->chain);
1539
1528
hb_waiters_inc(hb2);
1529
+
plist_add(&q->list, &hb2->chain);
1540
1530
q->lock_ptr = &hb2->lock;
1541
1531
}
1542
1532
get_futex_key_refs(key2);
···
2632
2622
*/
2633
2623
if (ret == -EFAULT)
2634
2624
goto pi_faulted;
2625
+
/*
2626
+
* A unconditional UNLOCK_PI op raced against a waiter
2627
+
* setting the FUTEX_WAITERS bit. Try again.
2628
+
*/
2629
+
if (ret == -EAGAIN) {
2630
+
spin_unlock(&hb->lock);
2631
+
put_futex_key(&key);
2632
+
goto retry;
2633
+
}
2635
2634
/*
2636
2635
* wake_futex_pi has detected invalid state. Tell user
2637
2636
* space.
+5
-3
kernel/locking/qspinlock_stat.h
+5
-3
kernel/locking/qspinlock_stat.h
···
136
136
}
137
137
138
138
if (counter == qstat_pv_hash_hops) {
139
-
u64 frac;
139
+
u64 frac = 0;
140
140
141
-
frac = 100ULL * do_div(stat, kicks);
142
-
frac = DIV_ROUND_CLOSEST_ULL(frac, kicks);
141
+
if (kicks) {
142
+
frac = 100ULL * do_div(stat, kicks);
143
+
frac = DIV_ROUND_CLOSEST_ULL(frac, kicks);
144
+
}
143
145
144
146
/*
145
147
* Return a X.XX decimal number