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Diffstat (limited to 'kernel/futex.c')
-rw-r--r--kernel/futex.c188
1 files changed, 117 insertions, 71 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index 9e40cf7be606..6262f1534ac9 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1311,13 +1311,15 @@ static int lookup_pi_state(u32 __user *uaddr, u32 uval,
static int lock_pi_update_atomic(u32 __user *uaddr, u32 uval, u32 newval)
{
+ int err;
u32 uninitialized_var(curval);
if (unlikely(should_fail_futex(true)))
return -EFAULT;
- if (unlikely(cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)))
- return -EFAULT;
+ err = cmpxchg_futex_value_locked(&curval, uaddr, uval, newval);
+ if (unlikely(err))
+ return err;
/* If user space value changed, let the caller retry */
return curval != uval ? -EAGAIN : 0;
@@ -1502,10 +1504,8 @@ static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_pi_state *pi_
if (unlikely(should_fail_futex(true)))
ret = -EFAULT;
- if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval)) {
- ret = -EFAULT;
-
- } else if (curval != uval) {
+ ret = cmpxchg_futex_value_locked(&curval, uaddr, uval, newval);
+ if (!ret && (curval != uval)) {
/*
* If a unconditional UNLOCK_PI operation (user space did not
* try the TID->0 transition) raced with a waiter setting the
@@ -1700,32 +1700,32 @@ retry_private:
double_lock_hb(hb1, hb2);
op_ret = futex_atomic_op_inuser(op, uaddr2);
if (unlikely(op_ret < 0)) {
-
double_unlock_hb(hb1, hb2);
-#ifndef CONFIG_MMU
- /*
- * we don't get EFAULT from MMU faults if we don't have an MMU,
- * but we might get them from range checking
- */
- ret = op_ret;
- goto out_put_keys;
-#endif
-
- if (unlikely(op_ret != -EFAULT)) {
+ if (!IS_ENABLED(CONFIG_MMU) ||
+ unlikely(op_ret != -EFAULT && op_ret != -EAGAIN)) {
+ /*
+ * we don't get EFAULT from MMU faults if we don't have
+ * an MMU, but we might get them from range checking
+ */
ret = op_ret;
goto out_put_keys;
}
- ret = fault_in_user_writeable(uaddr2);
- if (ret)
- goto out_put_keys;
+ if (op_ret == -EFAULT) {
+ ret = fault_in_user_writeable(uaddr2);
+ if (ret)
+ goto out_put_keys;
+ }
- if (!(flags & FLAGS_SHARED))
+ if (!(flags & FLAGS_SHARED)) {
+ cond_resched();
goto retry_private;
+ }
put_futex_key(&key2);
put_futex_key(&key1);
+ cond_resched();
goto retry;
}
@@ -2350,7 +2350,7 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
u32 uval, uninitialized_var(curval), newval;
struct task_struct *oldowner, *newowner;
u32 newtid;
- int ret;
+ int ret, err = 0;
lockdep_assert_held(q->lock_ptr);
@@ -2421,14 +2421,17 @@ retry:
if (!pi_state->owner)
newtid |= FUTEX_OWNER_DIED;
- if (get_futex_value_locked(&uval, uaddr))
- goto handle_fault;
+ err = get_futex_value_locked(&uval, uaddr);
+ if (err)
+ goto handle_err;
for (;;) {
newval = (uval & FUTEX_OWNER_DIED) | newtid;
- if (cmpxchg_futex_value_locked(&curval, uaddr, uval, newval))
- goto handle_fault;
+ err = cmpxchg_futex_value_locked(&curval, uaddr, uval, newval);
+ if (err)
+ goto handle_err;
+
if (curval == uval)
break;
uval = curval;
@@ -2456,23 +2459,37 @@ retry:
return 0;
/*
- * To handle the page fault we need to drop the locks here. That gives
- * the other task (either the highest priority waiter itself or the
- * task which stole the rtmutex) the chance to try the fixup of the
- * pi_state. So once we are back from handling the fault we need to
- * check the pi_state after reacquiring the locks and before trying to
- * do another fixup. When the fixup has been done already we simply
- * return.
+ * In order to reschedule or handle a page fault, we need to drop the
+ * locks here. In the case of a fault, this gives the other task
+ * (either the highest priority waiter itself or the task which stole
+ * the rtmutex) the chance to try the fixup of the pi_state. So once we
+ * are back from handling the fault we need to check the pi_state after
+ * reacquiring the locks and before trying to do another fixup. When
+ * the fixup has been done already we simply return.
*
* Note: we hold both hb->lock and pi_mutex->wait_lock. We can safely
* drop hb->lock since the caller owns the hb -> futex_q relation.
* Dropping the pi_mutex->wait_lock requires the state revalidate.
*/
-handle_fault:
+handle_err:
raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
spin_unlock(q->lock_ptr);
- ret = fault_in_user_writeable(uaddr);
+ switch (err) {
+ case -EFAULT:
+ ret = fault_in_user_writeable(uaddr);
+ break;
+
+ case -EAGAIN:
+ cond_resched();
+ ret = 0;
+ break;
+
+ default:
+ WARN_ON_ONCE(1);
+ ret = err;
+ break;
+ }
spin_lock(q->lock_ptr);
raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
@@ -3041,10 +3058,8 @@ retry:
* A unconditional UNLOCK_PI op raced against a waiter
* setting the FUTEX_WAITERS bit. Try again.
*/
- if (ret == -EAGAIN) {
- put_futex_key(&key);
- goto retry;
- }
+ if (ret == -EAGAIN)
+ goto pi_retry;
/*
* wake_futex_pi has detected invalid state. Tell user
* space.
@@ -3059,9 +3074,19 @@ retry:
* preserve the WAITERS bit not the OWNER_DIED one. We are the
* owner.
*/
- if (cmpxchg_futex_value_locked(&curval, uaddr, uval, 0)) {
+ if ((ret = cmpxchg_futex_value_locked(&curval, uaddr, uval, 0))) {
spin_unlock(&hb->lock);
- goto pi_faulted;
+ switch (ret) {
+ case -EFAULT:
+ goto pi_faulted;
+
+ case -EAGAIN:
+ goto pi_retry;
+
+ default:
+ WARN_ON_ONCE(1);
+ goto out_putkey;
+ }
}
/*
@@ -3075,6 +3100,11 @@ out_putkey:
put_futex_key(&key);
return ret;
+pi_retry:
+ put_futex_key(&key);
+ cond_resched();
+ goto retry;
+
pi_faulted:
put_futex_key(&key);
@@ -3435,6 +3465,7 @@ err_unlock:
static int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
{
u32 uval, uninitialized_var(nval), mval;
+ int err;
/* Futex address must be 32bit aligned */
if ((((unsigned long)uaddr) % sizeof(*uaddr)) != 0)
@@ -3444,42 +3475,57 @@ retry:
if (get_user(uval, uaddr))
return -1;
- if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) {
- /*
- * Ok, this dying thread is truly holding a futex
- * of interest. Set the OWNER_DIED bit atomically
- * via cmpxchg, and if the value had FUTEX_WAITERS
- * set, wake up a waiter (if any). (We have to do a
- * futex_wake() even if OWNER_DIED is already set -
- * to handle the rare but possible case of recursive
- * thread-death.) The rest of the cleanup is done in
- * userspace.
- */
- mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
- /*
- * We are not holding a lock here, but we want to have
- * the pagefault_disable/enable() protection because
- * we want to handle the fault gracefully. If the
- * access fails we try to fault in the futex with R/W
- * verification via get_user_pages. get_user() above
- * does not guarantee R/W access. If that fails we
- * give up and leave the futex locked.
- */
- if (cmpxchg_futex_value_locked(&nval, uaddr, uval, mval)) {
+ if ((uval & FUTEX_TID_MASK) != task_pid_vnr(curr))
+ return 0;
+
+ /*
+ * Ok, this dying thread is truly holding a futex
+ * of interest. Set the OWNER_DIED bit atomically
+ * via cmpxchg, and if the value had FUTEX_WAITERS
+ * set, wake up a waiter (if any). (We have to do a
+ * futex_wake() even if OWNER_DIED is already set -
+ * to handle the rare but possible case of recursive
+ * thread-death.) The rest of the cleanup is done in
+ * userspace.
+ */
+ mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
+
+ /*
+ * We are not holding a lock here, but we want to have
+ * the pagefault_disable/enable() protection because
+ * we want to handle the fault gracefully. If the
+ * access fails we try to fault in the futex with R/W
+ * verification via get_user_pages. get_user() above
+ * does not guarantee R/W access. If that fails we
+ * give up and leave the futex locked.
+ */
+ if ((err = cmpxchg_futex_value_locked(&nval, uaddr, uval, mval))) {
+ switch (err) {
+ case -EFAULT:
if (fault_in_user_writeable(uaddr))
return -1;
goto retry;
- }
- if (nval != uval)
+
+ case -EAGAIN:
+ cond_resched();
goto retry;
- /*
- * Wake robust non-PI futexes here. The wakeup of
- * PI futexes happens in exit_pi_state():
- */
- if (!pi && (uval & FUTEX_WAITERS))
- futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
+ default:
+ WARN_ON_ONCE(1);
+ return err;
+ }
}
+
+ if (nval != uval)
+ goto retry;
+
+ /*
+ * Wake robust non-PI futexes here. The wakeup of
+ * PI futexes happens in exit_pi_state():
+ */
+ if (!pi && (uval & FUTEX_WAITERS))
+ futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
+
return 0;
}
generated by cgit v1.2.3-70-g09d2 (git 2.47.1) at 2024-12-27 11:58:53 +0000