static keys: Introduce 'struct static_key', static_key_true()/false() and static_key_...
authorIngo Molnar <mingo@elte.hu>
Fri, 24 Feb 2012 07:31:31 +0000 (08:31 +0100)
committerIngo Molnar <mingo@elte.hu>
Fri, 24 Feb 2012 09:05:59 +0000 (10:05 +0100)
commitc5905afb0ee6550b42c49213da1c22d67316c194
tree253fdb322e6e5b257ffda3b9b66bce90a473a6f7
parent1cfa60dc7d7c7cc774a44eee47ff135a644a1f31
static keys: Introduce 'struct static_key', static_key_true()/false() and static_key_slow_[inc|dec]()

So here's a boot tested patch on top of Jason's series that does
all the cleanups I talked about and turns jump labels into a
more intuitive to use facility. It should also address the
various misconceptions and confusions that surround jump labels.

Typical usage scenarios:

        #include <linux/static_key.h>

        struct static_key key = STATIC_KEY_INIT_TRUE;

        if (static_key_false(&key))
                do unlikely code
        else
                do likely code

Or:

        if (static_key_true(&key))
                do likely code
        else
                do unlikely code

The static key is modified via:

        static_key_slow_inc(&key);
        ...
        static_key_slow_dec(&key);

The 'slow' prefix makes it abundantly clear that this is an
expensive operation.

I've updated all in-kernel code to use this everywhere. Note
that I (intentionally) have not pushed through the rename
blindly through to the lowest levels: the actual jump-label
patching arch facility should be named like that, so we want to
decouple jump labels from the static-key facility a bit.

On non-jump-label enabled architectures static keys default to
likely()/unlikely() branches.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Jason Baron <jbaron@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: a.p.zijlstra@chello.nl
Cc: mathieu.desnoyers@efficios.com
Cc: davem@davemloft.net
Cc: ddaney.cavm@gmail.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20120222085809.GA26397@elte.hu
Signed-off-by: Ingo Molnar <mingo@elte.hu>
31 files changed:
arch/Kconfig
arch/ia64/include/asm/paravirt.h
arch/ia64/kernel/paravirt.c
arch/mips/include/asm/jump_label.h
arch/powerpc/include/asm/jump_label.h
arch/s390/include/asm/jump_label.h
arch/sparc/include/asm/jump_label.h
arch/x86/include/asm/jump_label.h
arch/x86/include/asm/paravirt.h
arch/x86/kernel/kvm.c
arch/x86/kernel/paravirt.c
arch/x86/kvm/mmu_audit.c
include/linux/jump_label.h
include/linux/netdevice.h
include/linux/netfilter.h
include/linux/perf_event.h
include/linux/static_key.h [new file with mode: 0644]
include/linux/tracepoint.h
include/net/sock.h
kernel/events/core.c
kernel/jump_label.c
kernel/sched/core.c
kernel/sched/fair.c
kernel/sched/sched.h
kernel/tracepoint.c
net/core/dev.c
net/core/net-sysfs.c
net/core/sock.c
net/core/sysctl_net_core.c
net/ipv4/tcp_memcontrol.c
net/netfilter/core.c