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author | Peter Zijlstra <peterz@infradead.org> | 2015-07-24 15:09:55 +0200 |
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committer | Ingo Molnar <mingo@kernel.org> | 2015-08-03 11:34:15 +0200 |
commit | 11276d5306b8e5b438a36bbff855fe792d7eaa61 (patch) | |
tree | 9ddfc5e1bec6174e838cce8eb67af9e911c4e5f8 /arch/sparc/include/asm | |
parent | 706249c222f68471b6f8e9e8e9b77665c404b226 (diff) | |
download | op-kernel-dev-11276d5306b8e5b438a36bbff855fe792d7eaa61.zip op-kernel-dev-11276d5306b8e5b438a36bbff855fe792d7eaa61.tar.gz |
locking/static_keys: Add a new static_key interface
There are various problems and short-comings with the current
static_key interface:
- static_key_{true,false}() read like a branch depending on the key
value, instead of the actual likely/unlikely branch depending on
init value.
- static_key_{true,false}() are, as stated above, tied to the
static_key init values STATIC_KEY_INIT_{TRUE,FALSE}.
- we're limited to the 2 (out of 4) possible options that compile to
a default NOP because that's what our arch_static_branch() assembly
emits.
So provide a new static_key interface:
DEFINE_STATIC_KEY_TRUE(name);
DEFINE_STATIC_KEY_FALSE(name);
Which define a key of different types with an initial true/false
value.
Then allow:
static_branch_likely()
static_branch_unlikely()
to take a key of either type and emit the right instruction for the
case.
This means adding a second arch_static_branch_jump() assembly helper
which emits a JMP per default.
In order to determine the right instruction for the right state,
encode the branch type in the LSB of jump_entry::key.
This is the final step in removing the naming confusion that has led to
a stream of avoidable bugs such as:
a833581e372a ("x86, perf: Fix static_key bug in load_mm_cr4()")
... but it also allows new static key combinations that will give us
performance enhancements in the subsequent patches.
Tested-by: Rabin Vincent <rabin@rab.in> # arm
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> # ppc
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> # s390
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/sparc/include/asm')
-rw-r--r-- | arch/sparc/include/asm/jump_label.h | 35 |
1 files changed, 26 insertions, 9 deletions
diff --git a/arch/sparc/include/asm/jump_label.h b/arch/sparc/include/asm/jump_label.h index cc9b04a..62d0354 100644 --- a/arch/sparc/include/asm/jump_label.h +++ b/arch/sparc/include/asm/jump_label.h @@ -7,16 +7,33 @@ #define JUMP_LABEL_NOP_SIZE 4 -static __always_inline bool arch_static_branch(struct static_key *key) +static __always_inline bool arch_static_branch(struct static_key *key, bool branch) { - asm_volatile_goto("1:\n\t" - "nop\n\t" - "nop\n\t" - ".pushsection __jump_table, \"aw\"\n\t" - ".align 4\n\t" - ".word 1b, %l[l_yes], %c0\n\t" - ".popsection \n\t" - : : "i" (key) : : l_yes); + asm_volatile_goto("1:\n\t" + "nop\n\t" + "nop\n\t" + ".pushsection __jump_table, \"aw\"\n\t" + ".align 4\n\t" + ".word 1b, %l[l_yes], %c0\n\t" + ".popsection \n\t" + : : "i" (&((char *)key)[branch]) : : l_yes); + + return false; +l_yes: + return true; +} + +static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch) +{ + asm_volatile_goto("1:\n\t" + "b %l[l_yes]\n\t" + "nop\n\t" + ".pushsection __jump_table, \"aw\"\n\t" + ".align 4\n\t" + ".word 1b, %l[l_yes], %c0\n\t" + ".popsection \n\t" + : : "i" (&((char *)key)[branch]) : : l_yes); + return false; l_yes: return true; |