[PATCH 4.9 12/43] futex: Simplify fixup_pi_state_owner()

Greg Kroah-Hartman
2021-02-08T15:38:51Z

From: Thomas Gleixner <tglx@linutronix.de>

[ Upstream commit f2dac39d93987f7de1e20b3988c8685523247ae2 ]

Too many gotos already and an upcoming fix would make it even more
unreadable.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/futex.c | 41 +++++++++++++++++++++++++++--------------
1 file changed, 27 insertions(+), 14 deletions(-)

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2272,18 +2272,16 @@ static void unqueue_me_pi(struct futex_q
spin_unlock(q->lock_ptr);
}

-static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
- struct task_struct *argowner)
+static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
+ struct task_struct *argowner)
{
struct futex_pi_state *pi_state = q->pi_state;
- u32 uval, uninitialized_var(curval), newval;
struct task_struct *oldowner, *newowner;
- u32 newtid;
- int ret;
-
- lockdep_assert_held(q->lock_ptr);
+ u32 uval, curval, newval, newtid;
+ int err = 0;

oldowner = pi_state->owner;
+
/* Owner died? */
if (!pi_state->owner)
newtid |= FUTEX_OWNER_DIED;
@@ -2324,7 +2322,7 @@ retry:

if (__rt_mutex_futex_trylock(&pi_state->pi_mutex)) {
/* We got the lock after all, nothing to fix. */
- return 0;
+ return 1;
}

/*
@@ -2339,7 +2337,7 @@ retry:
* We raced against a concurrent self; things are
* already fixed up. Nothing to do.
*/
- return 0;
+ return 1;
}
newowner = argowner;
}
@@ -2380,7 +2378,7 @@ retry:
handle_fault:
spin_unlock(q->lock_ptr);

- ret = fault_in_user_writeable(uaddr);
+ err = fault_in_user_writeable(uaddr);

spin_lock(q->lock_ptr);

@@ -2388,12 +2386,27 @@ handle_fault:
* Check if someone else fixed it for us:
*/
if (pi_state->owner != oldowner)
- return 0;
+ return argowner == current;
+
+ /* Retry if err was -EAGAIN or the fault in succeeded */
+ if (!err)
+ goto retry;

- if (ret)
- return ret;
+ return err;
+}
+
+static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
+ struct task_struct *argowner)
+{
+ struct futex_pi_state *pi_state = q->pi_state;
+ int ret;
+
+ lockdep_assert_held(q->lock_ptr);

- goto retry;
+ raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
+ ret = __fixup_pi_state_owner(uaddr, q, argowner);
+ raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
+ return ret;
}

static long futex_wait_restart(struct restart_block *restart);