linux/include
Mark Rutland 2fde4f94e0 perf: Decouple unthrottling and rotating
Currently the adjusments made as part of perf_event_task_tick() use the
percpu rotation lists to iterate over any active PMU contexts, but these
are not used by the context rotation code, having been replaced by
separate (per-context) hrtimer callbacks. However, some manipulation of
the rotation lists (i.e. removal of contexts) has remained in
perf_rotate_context(). This leads to the following issues:

* Contexts are not always removed from the rotation lists. Removal of
  PMUs which have been placed in rotation lists, but have not been
  removed by a hrtimer callback can result in corruption of the rotation
  lists (when memory backing the context is freed).

  This has been observed to result in hangs when PMU drivers built as
  modules are inserted and removed around the creation of events for
  said PMUs.

* Contexts which do not require rotation may be removed from the
  rotation lists as a result of a hrtimer, and will not be considered by
  the unthrottling code in perf_event_task_tick.

This patch fixes the issue by updating the rotation ist when events are
scheduled in/out, ensuring that each rotation list stays in sync with
the HW state. As each event holds a refcount on the module of its PMU,
this ensures that when a PMU module is unloaded none of its CPU contexts
can be in a rotation list. By maintaining a list of perf_event_contexts
rather than perf_event_cpu_contexts, we don't need separate paths to
handle the cpu and task contexts, which also makes the code a little
simpler.

As the rotation_list variables are not used for rotation, these are
renamed to active_ctx_list, which better matches their current function.
perf_pmu_rotate_{start,stop} are renamed to
perf_pmu_ctx_{activate,deactivate}.

Reported-by: Johannes Jensen <johannes.jensen@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Will Deacon <Will.Deacon@arm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20150129134511.GR17721@leverpostej
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-04 08:07:16 +01:00
..
acpi ACPI / processor: Convert apic_id to phys_id to make it arch agnostic 2015-01-05 23:32:42 +01:00
asm-generic mm: mmu_gather: use tlb->end != 0 only for TLB invalidation 2015-01-13 15:20:40 +13:00
clocksource
crypto
drm Revert "drm/gem: Warn on illegal use of the dumb buffer interface v2" 2014-12-24 13:13:22 +10:00
dt-bindings ARM: dt: GIC: Spelling s/specific/specifier/, s/flaggs/flags/ 2015-01-13 13:48:16 -06:00
keys
kvm
linux perf: Decouple unthrottling and rotating 2015-02-04 08:07:16 +01:00
math-emu
media
memory
misc
net ipv4: try to cache dst_entries which would cause a redirect 2015-01-26 17:28:27 -08:00
pcmcia
ras
rdma
rxrpc
scsi SCSI for-linus on 20141220 2014-12-20 13:42:57 -08:00
soc
sound ALSA: pcm: Fix kerneldoc for params_*() functions 2014-12-30 16:41:11 +01:00
target target: Drop left-over fabric_max_sectors attribute 2015-01-09 15:22:05 -08:00
trace Merge branch 'perf/urgent' into perf/core, to pick up fixes 2015-01-28 15:42:56 +01:00
uapi Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2015-01-20 18:19:31 +12:00
video
xen x86/xen: properly retrieve NMI reason 2015-01-13 09:39:50 +00:00
Kbuild