linux-stable.git/arch/arm/kernel/perf_event.c, branch linux-3.19.y

ARM: 8255/1: perf: Prevent wraparound during overflow

2015-01-12T19:28:46+00:00

If the overflow threshold for a counter is set above or near the
0xffffffff boundary then the kernel may lose track of the overflow
causing only events that occur *after* the overflow to be recorded.
Specifically the problem occurs when the value of the performance counter
overtakes its original programmed value due to wrap around.

Typical solutions to this problem are either to avoid programming in
values likely to be overtaken or to treat the overflow bit as the 33rd
bit of the counter.

Its somewhat fiddly to refactor the code to correctly handle the 33rd bit
during irqsave sections (context switches for example) so instead we take
the simpler approach of avoiding values likely to be overtaken.

We set the limit to half of max_period because this matches the limit
imposed in __hw_perf_event_init(). This causes a doubling of the interrupt
rate for large threshold values, however even with a very fast counter
ticking at 4GHz the interrupt rate would only be ~1Hz.

Signed-off-by: Daniel Thompson 
Acked-by: Will Deacon 
Signed-off-by: Russell King

ARM / PM: Replace CONFIG_PM_RUNTIME with CONFIG_PM

2014-12-12T23:42:49+00:00

After commit b2b49ccbdd54 (PM: Kconfig: Set PM_RUNTIME if PM_SLEEP is
selected) PM_RUNTIME is always set if PM is set, so #ifdef blocks
depending on CONFIG_PM_RUNTIME may now be changed to depend on
CONFIG_PM.

Replace CONFIG_PM_RUNTIME with CONFIG_PM everywhere in the code under
arch/arm/ (the defconfig files will be modified later).

Signed-off-by: Rafael J. Wysocki 
Acked-by: Nishanth Menon 
Acked-by: Sekhar Nori 
Acked-by: Santosh Shilimkar

arm: perf: fold percpu_pmu into pmu_hw_events

2014-10-30T12:17:00+00:00

Currently the percpu_pmu pointers used as percpu_irq dev_id values are
defined separately from the other per-cpu accounting data, which make
dynamically allocating the data (as will be required for systems with
heterogeneous CPUs) difficult.

This patch moves the percpu_pmu pointers into pmu_hw_events (which is
itself allocated per cpu), which will allow for easier dynamic
allocation. Both percpu and regular irqs are requested using percpu_pmu
pointers as tokens, freeing us from having to know whether an irq is
percpu within the handler, and thus avoiding a radix tree lookup on the
handler path.

Signed-off-by: Mark Rutland 
Reviewed-by: Will Deacon 
Reviewed-by: Stephen Boyd 
Tested-by: Stephen Boyd 
Signed-off-by: Will Deacon

arm: perf: kill get_hw_events()

2014-10-30T12:17:00+00:00

Now that the arm pmu code is limited to CPU PMUs the get_hw_events()
function is superfluous, as we'll always have a set of per-cpu
pmu_hw_events structures.

This patch removes the get_hw_events() function, replacing it with
a percpu hw_events pointer. Uses of get_hw_events are updated to use
this_cpu_ptr.

Signed-off-by: Mark Rutland 
Reviewed-by: Will Deacon 
Reviewed-by: Stephen Boyd 
Signed-off-by: Will Deacon

arm: perf: limit size of accounting data

2014-10-30T12:16:59+00:00

Commit 3fc2c83087 (ARM: perf: remove event limit from pmu_hw_events) got
rid of the upper limit on the number of events an arm_pmu could handle,
but introduced additional complexity and places a burden on each PMU
driver to allocate accounting data somehow. So far this has not
generally been useful as the only users of arm_pmu are the CPU backend
and the CCI driver.

Now that the CCI driver plugs into the perf subsystem directly, we can
remove some of the complexities that get in the way of supporting
heterogeneous CPU PMUs.

This patch restores the original limits on pmu_hw_events fields such
that the pmu_hw_events data can be allocated as a contiguous block. This
will simplify dynamic pmu_hw_events allocation in later patches.

Signed-off-by: Mark Rutland 
Reviewed-by: Will Deacon 
Reviewed-by: Stephen Boyd 
Tested-by: Stephen Boyd 
Signed-off-by: Will Deacon

arm: perf: use IDR types for CPU PMUs

2014-10-30T12:16:59+00:00

For systems with heterogeneous CPUs (e.g. big.LITTLE systems) the PMUs
can be different in each cluster, and not all events can be migrated
between clusters. To allow userspace to deal with this, it must be
possible to address each PMU independently.

This patch changes PMUs to be registered with dynamic (IDR) types,
allowing them to be targeted individually. Each PMU's type can be found
in ${SYSFS_ROOT}/bus/event_source/devices/${PMU_NAME}/type.

From userspace, raw events can be targeted at a specific PMU:
$ perf stat -e ${PMU_NAME}/config=V,config1=V1,.../

Doing this does not break existing tools which use existing perf types:
when perf core can't find a PMU of matching type (in perf_init_event)
it'll iterate over the set of all PMUs. If a compatible PMU exists,
it'll be found eventually. If more than one compatible PMU exists, the
event will be handled by whichever PMU happens to be earlier in the pmus
list (which currently will be the last compatible PMU registered).

Signed-off-by: Mark Rutland 
Reviewed-by: Will Deacon 
Signed-off-by: Will Deacon

arm: perf: factor out callchain code

2014-10-30T12:16:58+00:00

The ARM callchain handling code is currently bundled with the ARM PMU
management code, despite the two having no dependency on each other.
This bundling has the unfortunate property of making callchain handling
depend on CONFIG_HW_PERF_EVENTS, even though the callchain handling
could be applied to software events in the absence of PMU hardware
support.

This patch separates the two, placing the callchain handling in
perf_callchain.c and making it depend on CONFIG_PERF_EVENTS rather than
CONFIG_HW_PERF_EVENTS, enabling callchain recording on kernels built
without hardware perf event support.

Signed-off-by: Mark Rutland 
Reviewed-by: Will Deacon 
Signed-off-by: Will Deacon

Merge branch 'devel-stable' into for-next

2014-08-05T09:27:25+00:00

Conflicts:
	arch/arm/kernel/perf_event_cpu.c

ARM: 8071/1: perf: Make perf use arm_get_current_stackframe

2014-07-18T11:29:12+00:00

Make the perf backend use the API so that it correctly references the FP
when in THUMB2 mode

Signed-off-by: Nikolay Borisov 
Acked-by: Will Deacon 
Signed-off-by: Russell King

ARM: perf: disable the pagefault handler when reading from user space

2014-07-09T14:05:29+00:00

Under perf, the fp unwinding scheme requires access to user space memory
and can provoke a pagefault via call to __copy_from_user_inatomic from
user_backtrace. This unwinding can take place in response to an interrupt
(__perf_event_overflow). This is undesirable as we may already have
mmap_sem held for write. One example being a process that calls mprotect
just as a the PMU counters overflow.

An example that can provoke this behaviour:
perf record -e event:tocapture --call-graph fp ./application_to_test

This patch addresses this issue by disabling pagefaults briefly in
user_backtrace (as is done in the other architectures: ARM64, x86, Sparc etc.).

Without the patch a deadlock occurs when __perf_event_overflow is called
while reading the data from the user space:

 [ INFO: possible recursive locking detected ]
 3.16.0-rc2-00038-g0ed7ff6 #46 Not tainted
 ---------------------------------------------
 stress/1634 is trying to acquire lock:
 (&mm->mmap_sem){++++++}, at: [] do_page_fault+0xa8/0x428

 but task is already holding lock:
 (&mm->mmap_sem){++++++}, at: [] SyS_mprotect+0xa8/0x1c8

 other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&mm->mmap_sem);
  lock(&mm->mmap_sem);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

 2 locks held by stress/1634:
 #0:  (&mm->mmap_sem){++++++}, at: [] SyS_mprotect+0xa8/0x1c8
 #1:  (rcu_read_lock){......}, at: [] __perf_event_overflow+0x120/0x294

 stack backtrace:
 CPU: 1 PID: 1634 Comm: stress Not tainted 3.16.0-rc2-00038-g0ed7ff6 #46
 [] (unwind_backtrace) from [] (show_stack+0x20/0x24)
 [] (show_stack) from [] (dump_stack+0x7c/0x98)
 [] (dump_stack) from [] (__lock_acquire+0x1484/0x1cf0)
 [] (__lock_acquire) from [] (lock_acquire+0xa4/0x11c)
 [] (lock_acquire) from [] (down_read+0x40/0x7c)
 [] (down_read) from [] (do_page_fault+0xa8/0x428)
 [] (do_page_fault) from [] (do_DataAbort+0x44/0xa8)
 [] (do_DataAbort) from [] (__dabt_svc+0x3c/0x60)
 Exception stack(0xed7c5ae0 to 0xed7c5b28)
 5ae0: ed7c5b5c b6dadff4 ffffffec 00000000 b6dadff4 ebc08000 00000000 ebc08000
 5b00: 0000007e 00000000 ed7c4000 ed7c5b94 00000014 ed7c5b2c c001a438 c0236c60
 5b20: 00000013 ffffffff
 [] (__dabt_svc) from [] (__copy_from_user+0xa4/0x3a4)

Acked-by: Steve Capper 
Signed-off-by: Jean Pihet 
Signed-off-by: Will Deacon