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Commit 04e1b2e5 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

futex: Split out the first waiter attachment from lookup_pi_state() 



We want to be a bit more clever in futex_lock_pi_atomic() and separate
the possible states. Split out the code which attaches the first
waiter to the owner into a separate function. No functional change.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarDarren 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/20140611204237.271300614@linutronix.de


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent e60cbc5c

kernel/futex.c

+28 −14
Original line number Diff line number Diff line
@@ -865,21 +865,16 @@ static int attach_to_pi_state(u32 uval, struct futex_pi_state *pi_state, 
	return 0;

}



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 task_struct *p;

	pid_t pid = uval & FUTEX_TID_MASK;



/*

	 * If there is a waiter on that futex, validate it and

	 * attach to the pi_state when the validation succeeds.

 * Lookup the task for the TID provided from user space and attach to

 * it after doing proper sanity checks.

 */

	if (match)

		return attach_to_pi_state(uval, match->pi_state, ps);

static int attach_to_pi_owner(u32 uval, union futex_key *key,

			      struct futex_pi_state **ps)

{

	pid_t pid = uval & FUTEX_TID_MASK;

	struct futex_pi_state *pi_state;

	struct task_struct *p;



	/*

	 * We are the first waiter - try to look up the real owner and attach
@@ -922,7 +917,7 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, 
	pi_state = alloc_pi_state();



	/*

	 * Initialize the pi_mutex in locked state and make 'p'

	 * Initialize the pi_mutex in locked state and make @p

	 * the owner of it:

	 */

	rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
@@ -942,6 +937,25 @@ lookup_pi_state(u32 uval, struct futex_hash_bucket *hb, 
	return 0;

}



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);



	/*

	 * If there is a waiter on that futex, validate it and

	 * attach to the pi_state when the validation succeeds.

	 */

	if (match)

		return attach_to_pi_state(uval, match->pi_state, ps);



	/*

	 * We are the first waiter - try to look up the owner based on

	 * @uval and attach to it.

	 */

	return attach_to_pi_owner(uval, key, ps);

}



/**

 * futex_lock_pi_atomic() - Atomic work required to acquire a pi aware futex

 * @uaddr:		the pi futex user address