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Subject[tip:locking/core] futex: Use futex_top_waiter() in lookup_pi_state()
Commit-ID:  bd1dbcc67cd2c1181e2c01daac51eabf1b964dd8
Gitweb: http://git.kernel.org/tip/bd1dbcc67cd2c1181e2c01daac51eabf1b964dd8
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 11 Jun 2014 20:45:39 +0000
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sat, 21 Jun 2014 22:26:23 +0200

futex: Use futex_top_waiter() in lookup_pi_state()

No point in open coding the same function again.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Darren Hart <darren@dvhart.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Kees Cook <kees@outflux.net>
Cc: wad@chromium.org
Link: http://lkml.kernel.org/r/20140611204237.092947239@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/futex.c | 124 ++++++++++++++++++++++++++++-----------------------------
1 file changed, 61 insertions(+), 63 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 346d5c2..fff1ed9 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -796,87 +796,85 @@ static int
lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
union futex_key *key, struct futex_pi_state **ps)
{
+ struct futex_q *match = futex_top_waiter(hb, key);
struct futex_pi_state *pi_state = NULL;
- struct futex_q *this, *next;
struct task_struct *p;
pid_t pid = uval & FUTEX_TID_MASK;

- plist_for_each_entry_safe(this, next, &hb->chain, list) {
- if (match_futex(&this->key, key)) {
- /*
- * Sanity check the waiter before increasing
- * the refcount and attaching to it.
- */
- pi_state = this->pi_state;
- /*
- * Userspace might have messed up non-PI and
- * PI futexes [3]
- */
- if (unlikely(!pi_state))
- return -EINVAL;
+ if (match) {
+ /*
+ * Sanity check the waiter before increasing the
+ * refcount and attaching to it.
+ */
+ pi_state = match->pi_state;
+ /*
+ * Userspace might have messed up non-PI and PI
+ * futexes [3]
+ */
+ if (unlikely(!pi_state))
+ return -EINVAL;

- WARN_ON(!atomic_read(&pi_state->refcount));
+ WARN_ON(!atomic_read(&pi_state->refcount));

+ /*
+ * Handle the owner died case:
+ */
+ if (uval & FUTEX_OWNER_DIED) {
/*
- * Handle the owner died case:
+ * exit_pi_state_list sets owner to NULL and
+ * wakes the topmost waiter. The task which
+ * acquires the pi_state->rt_mutex will fixup
+ * owner.
*/
- if (uval & FUTEX_OWNER_DIED) {
+ if (!pi_state->owner) {
/*
- * exit_pi_state_list sets owner to NULL and
- * wakes the topmost waiter. The task which
- * acquires the pi_state->rt_mutex will fixup
- * owner.
+ * No pi state owner, but the user
+ * space TID is not 0. Inconsistent
+ * state. [5]
*/
- if (!pi_state->owner) {
- /*
- * No pi state owner, but the user
- * space TID is not 0. Inconsistent
- * state. [5]
- */
- if (pid)
- return -EINVAL;
- /*
- * Take a ref on the state and
- * return. [4]
- */
- goto out_state;
- }
-
- /*
- * If TID is 0, then either the dying owner
- * has not yet executed exit_pi_state_list()
- * or some waiter acquired the rtmutex in the
- * pi state, but did not yet fixup the TID in
- * user space.
- *
- * Take a ref on the state and return. [6]
- */
- if (!pid)
- goto out_state;
- } else {
+ if (pid)
+ return -EINVAL;
/*
- * If the owner died bit is not set,
- * then the pi_state must have an
- * owner. [7]
+ * Take a ref on the state and
+ * return. [4]
*/
- if (!pi_state->owner)
- return -EINVAL;
+ goto out_state;
}

/*
- * Bail out if user space manipulated the
- * futex value. If pi state exists then the
- * owner TID must be the same as the user
- * space TID. [9/10]
+ * If TID is 0, then either the dying owner
+ * has not yet executed exit_pi_state_list()
+ * or some waiter acquired the rtmutex in the
+ * pi state, but did not yet fixup the TID in
+ * user space.
+ *
+ * Take a ref on the state and return. [6]
+ */
+ if (!pid)
+ goto out_state;
+ } else {
+ /*
+ * If the owner died bit is not set,
+ * then the pi_state must have an
+ * owner. [7]
*/
- if (pid != task_pid_vnr(pi_state->owner))
+ if (!pi_state->owner)
return -EINVAL;
-
- out_state:
- atomic_inc(&pi_state->refcount);
- *ps = pi_state;
- return 0;
}
+
+ /*
+ * Bail out if user space manipulated the
+ * futex value. If pi state exists then the
+ * owner TID must be the same as the user
+ * space TID. [9/10]
+ */
+ if (pid != task_pid_vnr(pi_state->owner))
+ return -EINVAL;
+
+ out_state:
+ atomic_inc(&pi_state->refcount);
+ *ps = pi_state;
+ return 0;
}

/*

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