[tip PATCH v7 2/9] RFC: futex: futex_top_waiter()

Darren Hart
2009-04-03T20:40:52Z

Improve legibility by wrapping finding the top waiter in a function. This
will be used by the follow-on patches for enabling requeue pi.

Changelog:
V7: -Minor kernel doc comment update
V6: -Shortened function length after review from tglx
-Corrected kernel-doc formatting
V4: -Simplified logic in the hb loop
-Return the futex_q as the task can be had from there if needed
-Updated comments and dropped the -safe iterator per review from tglx
V3: -Comment linewidth cleanup
V1: -Initial version

Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Reviewed-by: Steven Rostedt <srostedt@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sripathi Kodi <sripathik@in.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Dinakar Guniguntala <dino@in.ibm.com>
Cc: Ulrich Drepper <drepper@redhat.com>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jakub Jelinek <jakub@redhat.com>
---

kernel/futex.c | 19 +++++++++++++++++++
1 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index d1d3e67..a13369d 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -276,6 +276,25 @@ void put_futex_key(int fshared, union futex_key *key)
drop_futex_key_refs(key);
}

+/**
+ * futex_top_waiter() - Return the highest priority waiter on a futex
+ * @hb: the hash bucket the futex_q's reside in
+ * @key: the futex key (to distinguish it from other futex futex_q's)
+ *
+ * Must be called with the hb lock held.
+ */
+static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb,
+ union futex_key *key)
+{
+ struct futex_q *this;
+
+ plist_for_each_entry(this, &hb->chain, list) {
+ if (match_futex(&this->key, key))
+ return this;
+ }
+ return NULL;
+}
+
static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
{
u32 curval;