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2015-08-03locking/static_keys: Add selftestPeter Zijlstra1-1/+38
Add a little selftest that validates all combinations. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> 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>
2015-08-03locking/static_keys: Add a new static_key interfacePeter Zijlstra1-7/+30
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>
2015-08-03locking/static_keys: Rework update logicPeter Zijlstra1-50/+38
Instead of spreading the branch_default logic all over the place, concentrate it into the one jump_label_type() function. This does mean we need to actually increment/decrement the enabled count _before_ calling the update path, otherwise jump_label_type() will not see the right state. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> 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>
2015-08-03jump_label: Add jump_entry_key() helperPeter Zijlstra1-4/+9
Avoid some casting with a helper, also prepares the way for overloading the LSB of jump_entry::key. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> 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>
2015-08-03jump_label, locking/static_keys: Rename JUMP_LABEL_TYPE_* and related ↵Peter Zijlstra1-9/+16
helpers to the static_key* pattern Rename the JUMP_LABEL_TYPE_* macros to be JUMP_TYPE_* and move the inline helpers into kernel/jump_label.c, since that's the only place they're ever used. Also rename the helpers where it's all about static keys. This is the second 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()") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> 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>
2015-08-03jump_label: Rename JUMP_LABEL_{EN,DIS}ABLE to JUMP_LABEL_{JMP,NOP}Peter Zijlstra1-9/+9
Since we've already stepped away from ENABLE is a JMP and DISABLE is a NOP with the branch_default bits, and are going to make it even worse, rename it to make it all clearer. This way we don't mix multiple levels of logic attributes, but have a plain 'physical' name for what the current instruction patching status of a jump label is. This is a first 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()") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> 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 [ Beefed up the changelog. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-05-27module, jump_label: Fix module lockingPeter Zijlstra1-4/+6
As per the module core lockdep annotations in the coming patch: [ 18.034047] ---[ end trace 9294429076a9c673 ]--- [ 18.047760] Hardware name: Intel Corporation S2600GZ/S2600GZ, BIOS SE5C600.86B.02.02.0002.122320131210 12/23/2013 [ 18.059228] ffffffff817d8676 ffff880036683c38 ffffffff8157e98b 0000000000000001 [ 18.067541] 0000000000000000 ffff880036683c78 ffffffff8105fbc7 ffff880036683c68 [ 18.075851] ffffffffa0046b08 0000000000000000 ffffffffa0046d00 ffffffffa0046cc8 [ 18.084173] Call Trace: [ 18.086906] [<ffffffff8157e98b>] dump_stack+0x4f/0x7b [ 18.092649] [<ffffffff8105fbc7>] warn_slowpath_common+0x97/0xe0 [ 18.099361] [<ffffffff8105fc2a>] warn_slowpath_null+0x1a/0x20 [ 18.105880] [<ffffffff810ee502>] __module_address+0x1d2/0x1e0 [ 18.112400] [<ffffffff81161153>] jump_label_module_notify+0x143/0x1e0 [ 18.119710] [<ffffffff810814bf>] notifier_call_chain+0x4f/0x70 [ 18.126326] [<ffffffff8108160e>] __blocking_notifier_call_chain+0x5e/0x90 [ 18.134009] [<ffffffff81081656>] blocking_notifier_call_chain+0x16/0x20 [ 18.141490] [<ffffffff810f0f00>] load_module+0x1b50/0x2660 [ 18.147720] [<ffffffff810f1ade>] SyS_init_module+0xce/0x100 [ 18.154045] [<ffffffff81587429>] system_call_fastpath+0x12/0x17 [ 18.160748] ---[ end trace 9294429076a9c674 ]--- Jump labels is not doing it right; fix this. Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Jason Baron <jbaron@akamai.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2013-10-20static_key: WARN on usage before jump_label_init was calledHannes Frederic Sowa1-0/+5
Usage of the static key primitives to toggle a branch must not be used before jump_label_init() is called from init/main.c. jump_label_init reorganizes and wires up the jump_entries so usage before that could have unforeseen consequences. Following primitives are now checked for correct use: * static_key_slow_inc * static_key_slow_dec * static_key_slow_dec_deferred * jump_label_rate_limit The x86 architecture already checks this by testing if the default_nop was already replaced with an optimal nop or with a branch instruction. It will panic then. Other architectures don't check for this. Because we need to relax this check for the x86 arch to allow code to transition from default_nop to the enabled state and other architectures did not check for this at all this patch introduces checking on the static_key primitives in a non-arch dependent manner. All checked functions are considered slow-path so the additional check does no harm to performance. The warnings are best observed with earlyprintk. Based on a patch from Andi Kleen. Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Andi Kleen <andi@firstfloor.org> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-08-09jump_label: Split jumplabel ratelimitAndrew Jones1-0/+1
Commit b202952075f62603bea9bfb6ebc6b0420db11949 ("perf, core: Rate limit perf_sched_events jump_label patching") introduced rate limiting for jump label disabling. The changes were made in the jump label code in order to be more widely available and to keep things tidier. This is all fine, except now jump_label.h includes linux/workqueue.h, which makes it impossible to include jump_label.h from anything that workqueue.h needs. For example, it's now impossible to include jump_label.h from asm/spinlock.h, which is done in proposed pv-ticketlock patches. This patch splits out the rate limiting related changes from jump_label.h into a new file, jump_label_ratelimit.h, to resolve the issue. Signed-off-by: Andrew Jones <drjones@redhat.com> Link: http://lkml.kernel.org/r/1376058122-8248-10-git-send-email-raghavendra.kt@linux.vnet.ibm.com Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> Acked-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
2012-08-06jump_label: Export jump_label_rate_limit()Gleb Natapov1-0/+1
CC: Jason Baron <jbaron@redhat.com> CC: Ingo Molnar <mingo@elte.hu> CC: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Gleb Natapov <gleb@redhat.com> Acked-by: Jason Baron <jbaron@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
2012-02-28static keys: Inline the static_key_enabled() functionJason Baron1-6/+0
In the jump label enabled case, calling static_key_enabled() results in a function call. The function returns the results of a compare, so it really doesn't need the overhead of a full function call. Let's make it 'static inline' for both the jump label enabled and disabled cases. Signed-off-by: Jason Baron <jbaron@redhat.com> Cc: a.p.zijlstra@chello.nl Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@polymtl.ca Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/201202281849.q1SIn1p2023270@int-mx10.intmail.prod.int.phx2.redhat.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-24static keys: Introduce 'struct static_key', static_key_true()/false() and ↵Ingo Molnar1-54/+74
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>
2012-02-22jump label: Fix compiler warningJason Baron1-1/+1
While cross-compiling on sparc64, I found: kernel/jump_label.c: In function 'jump_label_update': kernel/jump_label.c:447:40: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] Fix by casting to 'unsigned long'. Signed-off-by: Jason Baron <jbaron@redhat.com> Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: davem@davemloft.net Cc: ddaney.cavm@gmail.com Cc: a.p.zijlstra@chello.nl Link: http://lkml.kernel.org/r/08026cbc6df80619cae833ef1ebbbc43efab69ab.1329851692.git.jbaron@redhat.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2012-02-22jump label: Add a WARN() if jump label key count goes negativeJason Baron1-1/+4
The count on a jump label key should never go negative. Add a WARN() to check for this condition. Signed-off-by: Jason Baron <jbaron@redhat.com> Cc: Gleb Natapov <gleb@redhat.com> Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: davem@davemloft.net Cc: ddaney.cavm@gmail.com Cc: a.p.zijlstra@chello.nl Link: http://lkml.kernel.org/r/3c68556121be4d1920417a3fe367da1ec38246b4.1329851692.git.jbaron@redhat.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-27Merge remote-tracking branch 'tip/perf/core' into kvm-updates/3.3Avi Kivity1-7/+42
* tip/perf/core: (66 commits) perf, x86: Expose perf capability to other modules perf, x86: Implement arch event mask as quirk x86, perf: Disable non available architectural events jump_label: Provide jump_label_key initializers jump_label, x86: Fix section mismatch perf, core: Rate limit perf_sched_events jump_label patching perf: Fix enable_on_exec for sibling events perf: Remove superfluous arguments perf, x86: Prefer fixed-purpose counters when scheduling perf, x86: Fix event scheduler for constraints with overlapping counters perf, x86: Implement event scheduler helper functions perf: Avoid a useless pmu_disable() in the perf-tick x86/tools: Add decoded instruction dump mode x86: Update instruction decoder to support new AVX formats x86/tools: Fix insn_sanity message outputs x86/tools: Fix instruction decoder message output x86: Fix instruction decoder to handle grouped AVX instructions x86/tools: Fix Makefile to build all test tools perf test: Soft errors shouldn't stop the "Validate PERF_RECORD_" test perf test: Validate PERF_RECORD_ events and perf_sample fields ... Signed-off-by: Avi Kivity <avi@redhat.com> * commit 'b3d9468a8bd218a695e3a0ff112cd4efd27b670a': (66 commits) perf, x86: Expose perf capability to other modules perf, x86: Implement arch event mask as quirk x86, perf: Disable non available architectural events jump_label: Provide jump_label_key initializers jump_label, x86: Fix section mismatch perf, core: Rate limit perf_sched_events jump_label patching perf: Fix enable_on_exec for sibling events perf: Remove superfluous arguments perf, x86: Prefer fixed-purpose counters when scheduling perf, x86: Fix event scheduler for constraints with overlapping counters perf, x86: Implement event scheduler helper functions perf: Avoid a useless pmu_disable() in the perf-tick x86/tools: Add decoded instruction dump mode x86: Update instruction decoder to support new AVX formats x86/tools: Fix insn_sanity message outputs x86/tools: Fix instruction decoder message output x86: Fix instruction decoder to handle grouped AVX instructions x86/tools: Fix Makefile to build all test tools perf test: Soft errors shouldn't stop the "Validate PERF_RECORD_" test perf test: Validate PERF_RECORD_ events and perf_sample fields ...
2011-12-27jump-label: export jump_label_inc/jump_label_decXiao Guangrong1-0/+2
Export these two symbols, they will be used by KVM mmu audit Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Signed-off-by: Avi Kivity <avi@redhat.com>
2011-12-06jump_label: Provide jump_label_key initializersPeter Zijlstra1-4/+8
Provide two initializers for jump_label_key that initialize it enabled or disabled. Also modify all jump_label code to allow for jump_labels to be initialized enabled. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Jason Baron <jbaron@redhat.com> Link: http://lkml.kernel.org/n/tip-p40e3yj21b68y03z1yv825e7@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06jump_label, x86: Fix section mismatchPeter Zijlstra1-1/+1
WARNING: arch/x86/kernel/built-in.o(.text+0x4c71): Section mismatch in reference from the function arch_jump_label_transform_static() to the function .init.text:text_poke_early() The function arch_jump_label_transform_static() references the function __init text_poke_early(). This is often because arch_jump_label_transform_static lacks a __init annotation or the annotation of text_poke_early is wrong. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Jason Baron <jbaron@redhat.com> Link: http://lkml.kernel.org/n/tip-9lefe89mrvurrwpqw5h8xm8z@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-06perf, core: Rate limit perf_sched_events jump_label patchingGleb Natapov1-2/+33
jump_lable patching is very expensive operation that involves pausing all cpus. The patching of perf_sched_events jump_label is easily controllable from userspace by unprivileged user. When te user runs a loop like this: "while true; do perf stat -e cycles true; done" ... the performance of my test application that just increments a counter for one second drops by 4%. This is on a 16 cpu box with my test application using only one of them. An impact on a real server doing real work will be worse. Performance of KVM PMU drops nearly 50% due to jump_lable for "perf record" since KVM PMU implementation creates and destroys perf event frequently. This patch introduces a way to rate limit jump_label patching and uses it to fix the above problem. I believe that as jump_label use will spread the problem will become more common and thus solving it in a generic code is appropriate. Also fixing it in the perf code would result in moving jump_label accounting logic to perf code with all the ifdefs in case of JUMP_LABEL=n kernel. With this patch all details are nicely hidden inside jump_label code. Signed-off-by: Gleb Natapov <gleb@redhat.com> Acked-by: Jason Baron <jbaron@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20111127155909.GO2557@redhat.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
2011-12-05jump_label: jump_label_inc may return before the code is patchedGleb Natapov1-1/+2
If cpu A calls jump_label_inc() just after atomic_add_return() is called by cpu B, atomic_inc_not_zero() will return value greater then zero and jump_label_inc() will return to a caller before jump_label_update() finishes its job on cpu B. Link: http://lkml.kernel.org/r/20111018175551.GH17571@redhat.com Cc: stable@vger.kernel.org Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Jason Baron <jbaron@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-11-11Merge branch 'tip/perf/core' of ↵Ingo Molnar1-1/+2
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace into perf/core
2011-11-07jump_label: jump_label_inc may return before the code is patchedGleb Natapov1-1/+2
If cpu A calls jump_label_inc() just after atomic_add_return() is called by cpu B, atomic_inc_not_zero() will return value greater then zero and jump_label_inc() will return to a caller before jump_label_update() finishes its job on cpu B. Link: http://lkml.kernel.org/r/20111018175551.GH17571@redhat.com Cc: stable@vger.kernel.org Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Jason Baron <jbaron@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-10-25jump-label: initialize jump-label subsystem much earlierJeremy Fitzhardinge1-4/+1
Initialize jump_labels much, much earlier, so they're available for use during system setup. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
2011-10-25jump_label: add arch_jump_label_transform_static() to optimise non-live code ↵Jeremy Fitzhardinge1-3/+15
updates When updating a newly loaded module, the code is definitely not yet executing on any processor, so it can be updated with no need for any heavyweight synchronization. This patch adds arch_jump_label_static() which is implemented as arch_jump_label_transform() by default, but architectures can override it if it avoids, say, a call to stop_machine(). Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Acked-by: Jason Baron <jbaron@redhat.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
2011-10-25jump_label: if a key has already been initialized, don't nop it outJeremy Fitzhardinge1-12/+8
If a key has been enabled before jump_label_init() is called, don't nop it out. This removes arch_jump_label_text_poke_early() (which can only nop out a site) and uses arch_jump_label_transform() instead. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Acked-by: Jason Baron <jbaron@redhat.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
2011-06-29jump_label: Fix jump_label update for modulesXiao Guangrong1-5/+9
The jump labels entries for modules do not stop at __stop__jump_table, but after mod->jump_entries + mod_num_jump_entries. By checking the wrong end point, module trace events never get enabled. Cc: Ingo Molnar <mingo@elte.hu> Acked-by: Jason Baron <jbaron@redhat.com> Tested-by: Avi Kivity <avi@redhat.com> Tested-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> Link: http://lkml.kernel.org/r/4E00038B.2060404@cn.fujitsu.com Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-05-26jump_label: Check entries limit in __jump_label_updateJiri Olsa1-5/+13
When iterating the jump_label entries array (core or modules), the __jump_label_update function peeks over the last entry. The reason is that the end of the for loop depends on the key value of the processed entry. Thus when going through the last array entry, we will touch the memory behind the array limit. This bug probably will never be triggered, since most likely the memory behind the jump_label entries will be accesable and the entry->key will be different than the expected value. Signed-off-by: Jiri Olsa <jolsa@redhat.com> Acked-by: Jason Baron <jbaron@redhat.com> Link: http://lkml.kernel.org/r/20110510104346.GC1899@jolsa.brq.redhat.com Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2011-04-04jump label: Introduce static_branch() interfaceJason Baron1-321/+218
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>
2010-10-29jump label: Make arch_jump_label_text_poke_early() optionalSteven Rostedt1-0/+7
Some archs do not need to do anything special for jump labels on startup (like MIPS). This patch adds a weak function stub for arch_jump_label_text_poke_early(); Cc: Jason Baron <jbaron@redhat.com> Cc: David Miller <davem@davemloft.net> Cc: David Daney <ddaney@caviumnetworks.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> LKML-Reference: <1286218615-24011-2-git-send-email-ddaney@caviumnetworks.com> LKML-Reference: <20101015201037.703989993@goodmis.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-10-28jump label: Fix deadlock b/w jump_label_mutex vs. text_mutexJason Baron1-12/+21
register_kprobe() downs the 'text_mutex' and then calls jump_label_text_reserved(), which downs the 'jump_label_mutex'. However, the jump label code takes those mutexes in the reverse order. Fix by requiring the caller of jump_label_text_reserved() to do the jump label locking via the newly added: jump_label_lock(), jump_label_unlock(). Currently, kprobes is the only user of jump_label_text_reserved(). Reported-by: Ingo Molnar <mingo@elte.hu> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Jason Baron <jbaron@redhat.com> LKML-Reference: <759032c48d5e30c27f0bba003d09bffa8e9f28bb.1285965957.git.jbaron@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-10-28jump label: Fix module __init section raceJason Baron1-1/+40
Jump label uses is_module_text_address() to ensure that the module __init sections are valid before updating them. However, between the check for a valid module __init section and the subsequent jump label update, the module's __init section could be freed out from under us. We fix this potential race by adding a notifier callback to the MODULE_STATE_LIVE state. This notifier is called *after* the __init section has been run but before it is going to be freed. In the callback, the jump label code zeros the key value for any __init jump code within the module, and we add a check for a non-zero key value when we update jump labels. In this way we require no additional data structures. Thanks to Mathieu Desnoyers for pointing out this race condition. Reported-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Jason Baron <jbaron@redhat.com> LKML-Reference: <c6f037b7598777668025ceedd9294212fd95fa34.1285965957.git.jbaron@redhat.com> [ Renamed remove_module_init() to remove_jump_label_module_init() as suggested by Masami Hiramatsu. ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-09-23jump label: Add jump_label_text_reserved() to reserve jump pointsJason Baron1-0/+83
Add a jump_label_text_reserved(void *start, void *end), so that other pieces of code that want to modify kernel text, can first verify that jump label has not reserved the instruction. Acked-by: Masami Hiramatsu <mhiramat@redhat.com> Signed-off-by: Jason Baron <jbaron@redhat.com> LKML-Reference: <06236663a3a7b1c1f13576bb9eccb6d9c17b7bfe.1284733808.git.jbaron@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2010-09-23jump label: Base patch for jump labelJason Baron1-0/+346
base patch to implement 'jump labeling'. Based on a new 'asm goto' inline assembly gcc mechanism, we can now branch to labels from an 'asm goto' statment. This allows us to create a 'no-op' fastpath, which can subsequently be patched with a jump to the slowpath code. This is useful for code which might be rarely used, but which we'd like to be able to call, if needed. Tracepoints are the current usecase that these are being implemented for. Acked-by: David S. Miller <davem@davemloft.net> Signed-off-by: Jason Baron <jbaron@redhat.com> LKML-Reference: <ee8b3595967989fdaf84e698dc7447d315ce972a.1284733808.git.jbaron@redhat.com> [ cleaned up some formating ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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