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authorJason Baron <jbaron@redhat.com>2011-03-16 22:29:47 +0100
committerSteven Rostedt <rostedt@goodmis.org>2011-04-04 18:48:08 +0200
commitd430d3d7e646eb1eac2bb4aa244a644312e67c76 (patch)
tree0f52534f54d89e41042536ff2f1b2ce74c45c033 /arch/mips
parenttracing: Avoid soft lockup in trace_pipe (diff)
downloadlinux-d430d3d7e646eb1eac2bb4aa244a644312e67c76.tar.xz
linux-d430d3d7e646eb1eac2bb4aa244a644312e67c76.zip
jump label: Introduce static_branch() interface
Introduce: static __always_inline bool static_branch(struct jump_label_key *key); instead of the old JUMP_LABEL(key, label) macro. In this way, jump labels become really easy to use: Define: struct jump_label_key jump_key; Can be used as: if (static_branch(&jump_key)) do unlikely code enable/disale via: jump_label_inc(&jump_key); jump_label_dec(&jump_key); that's it! For the jump labels disabled case, the static_branch() becomes an atomic_read(), and jump_label_inc()/dec() are simply atomic_inc(), atomic_dec() operations. We show testing results for this change below. Thanks to H. Peter Anvin for suggesting the 'static_branch()' construct. Since we now require a 'struct jump_label_key *key', we can store a pointer into the jump table addresses. In this way, we can enable/disable jump labels, in basically constant time. This change allows us to completely remove the previous hashtable scheme. Thanks to Peter Zijlstra for this re-write. Testing: I ran a series of 'tbench 20' runs 5 times (with reboots) for 3 configurations, where tracepoints were disabled. jump label configured in avg: 815.6 jump label *not* configured in (using atomic reads) avg: 800.1 jump label *not* configured in (regular reads) avg: 803.4 Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20110316212947.GA8792@redhat.com> Signed-off-by: Jason Baron <jbaron@redhat.com> Suggested-by: H. Peter Anvin <hpa@linux.intel.com> Tested-by: David Daney <ddaney@caviumnetworks.com> Acked-by: Ralf Baechle <ralf@linux-mips.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'arch/mips')
-rw-r--r--arch/mips/include/asm/jump_label.h22
1 files changed, 12 insertions, 10 deletions
diff --git a/arch/mips/include/asm/jump_label.h b/arch/mips/include/asm/jump_label.h
index 7622ccf75076..1881b316ca45 100644
--- a/arch/mips/include/asm/jump_label.h
+++ b/arch/mips/include/asm/jump_label.h
@@ -20,16 +20,18 @@
#define WORD_INSN ".word"
#endif
-#define JUMP_LABEL(key, label) \
- do { \
- asm goto("1:\tnop\n\t" \
- "nop\n\t" \
- ".pushsection __jump_table, \"a\"\n\t" \
- WORD_INSN " 1b, %l[" #label "], %0\n\t" \
- ".popsection\n\t" \
- : : "i" (key) : : label); \
- } while (0)
-
+static __always_inline bool arch_static_branch(struct jump_label_key *key)
+{
+ asm goto("1:\tnop\n\t"
+ "nop\n\t"
+ ".pushsection __jump_table, \"aw\"\n\t"
+ WORD_INSN " 1b, %l[l_yes], %0\n\t"
+ ".popsection\n\t"
+ : : "i" (key) : : l_yes);
+ return false;
+l_yes:
+ return true;
+}
#endif /* __KERNEL__ */