linux-toradex.git/kernel/jump_label.c, branch v4.6-rc6

treewide: Remove old email address

2015-11-23T08:44:58+00:00

There were still a number of references to my old Red Hat email
address in the kernel source. Remove these while keeping the
Red Hat copyright notices intact.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: Arnaldo Carvalho de Melo 
Cc: Jiri Olsa 
Cc: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Stephane Eranian 
Cc: Thomas Gleixner 
Cc: Vince Weaver 
Signed-off-by: Ingo Molnar

locking/static_keys: Add selftest

2015-08-03T09:34:16+00:00

Add a little selftest that validates all combinations.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

locking/static_keys: Add a new static_key interface

2015-08-03T09:34:15+00:00

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  # arm
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Michael Ellerman  # ppc
Acked-by: Heiko Carstens  # s390
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

locking/static_keys: Rework update logic

2015-08-03T09:34:15+00:00

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) 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

jump_label: Add jump_entry_key() helper

2015-08-03T09:34:14+00:00

Avoid some casting with a helper, also prepares the way for
overloading the LSB of jump_entry::key.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

jump_label, locking/static_keys: Rename JUMP_LABEL_TYPE_* and related helpers to the static_key* pattern

2015-08-03T09:34:13+00:00

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) 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

jump_label: Rename JUMP_LABEL_{EN,DIS}ABLE to JUMP_LABEL_{JMP,NOP}

2015-08-03T09:34:12+00:00

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) 
Cc: Andrew Morton 
Cc: Linus Torvalds 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
[ Beefed up the changelog. ]
Signed-off-by: Ingo Molnar

module, jump_label: Fix module locking

2015-05-27T01:39:50+00:00

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]  [] dump_stack+0x4f/0x7b
[   18.092649]  [] warn_slowpath_common+0x97/0xe0
[   18.099361]  [] warn_slowpath_null+0x1a/0x20
[   18.105880]  [] __module_address+0x1d2/0x1e0
[   18.112400]  [] jump_label_module_notify+0x143/0x1e0
[   18.119710]  [] notifier_call_chain+0x4f/0x70
[   18.126326]  [] __blocking_notifier_call_chain+0x5e/0x90
[   18.134009]  [] blocking_notifier_call_chain+0x16/0x20
[   18.141490]  [] load_module+0x1b50/0x2660
[   18.147720]  [] SyS_init_module+0xce/0x100
[   18.154045]  [] system_call_fastpath+0x12/0x17
[   18.160748] ---[ end trace 9294429076a9c674 ]---

Jump labels is not doing it right; fix this.

Cc: Rusty Russell 
Cc: Jason Baron 
Acked-by: Paul E. McKenney 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Rusty Russell

static_key: WARN on usage before jump_label_init was called

2013-10-19T23:45:35+00:00

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 
Cc: Peter Zijlstra 
Cc: Andi Kleen 
Signed-off-by: Hannes Frederic Sowa 
Signed-off-by: David S. Miller

jump_label: Split jumplabel ratelimit

2013-08-09T14:53:54+00:00

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 
Link: http://lkml.kernel.org/r/1376058122-8248-10-git-send-email-raghavendra.kt@linux.vnet.ibm.com
Reviewed-by: Konrad Rzeszutek Wilk 
Signed-off-by: Raghavendra K T 
Acked-by: Ingo Molnar 
Signed-off-by: H. Peter Anvin