From 26333576fd0d0b52f6e4025c5aded97e188bdd44 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Thu, 18 Oct 2007 03:06:39 -0700 Subject: bitops: introduce lock ops Introduce test_and_set_bit_lock / clear_bit_unlock bitops with lock semantics. Convert all architectures to use the generic implementation. Signed-off-by: Nick Piggin Acked-By: David Howells Cc: Richard Henderson Cc: Ivan Kokshaysky Cc: Russell King Cc: Haavard Skinnemoen Cc: Bryan Wu Cc: Mikael Starvik Cc: David Howells Cc: Yoshinori Sato Cc: "Luck, Tony" Cc: Hirokazu Takata Cc: Geert Uytterhoeven Cc: Roman Zippel Cc: Greg Ungerer Cc: Ralf Baechle Cc: Kyle McMartin Cc: Matthew Wilcox Cc: Paul Mackerras Cc: Benjamin Herrenschmidt Cc: Heiko Carstens Cc: Martin Schwidefsky Cc: Paul Mundt Cc: Kazumoto Kojima Cc: Richard Curnow Cc: William Lee Irwin III Cc: "David S. Miller" Cc: Jeff Dike Cc: Paolo 'Blaisorblade' Giarrusso Cc: Miles Bader Cc: Andi Kleen Cc: Chris Zankel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/atomic_ops.txt | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'Documentation/atomic_ops.txt') diff --git a/Documentation/atomic_ops.txt b/Documentation/atomic_ops.txt index d46306fea230..f20c10c2858f 100644 --- a/Documentation/atomic_ops.txt +++ b/Documentation/atomic_ops.txt @@ -418,6 +418,20 @@ brothers: */ smp_mb__after_clear_bit(); +There are two special bitops with lock barrier semantics (acquire/release, +same as spinlocks). These operate in the same way as their non-_lock/unlock +postfixed variants, except that they are to provide acquire/release semantics, +respectively. This means they can be used for bit_spin_trylock and +bit_spin_unlock type operations without specifying any more barriers. + + int test_and_set_bit_lock(unsigned long nr, unsigned long *addr); + void clear_bit_unlock(unsigned long nr, unsigned long *addr); + void __clear_bit_unlock(unsigned long nr, unsigned long *addr); + +The __clear_bit_unlock version is non-atomic, however it still implements +unlock barrier semantics. This can be useful if the lock itself is protecting +the other bits in the word. + Finally, there are non-atomic versions of the bitmask operations provided. They are used in contexts where some other higher-level SMP locking scheme is being used to protect the bitmask, and thus less -- cgit v1.2.3