Commit Graph

19846 Commits

Author SHA1 Message Date
Kan Liang
2ed11312eb Revert "perf: Remove the extra validity check on nr_pages"
This reverts commit 74390aa556 ("perf: Remove the extra validity check
on nr_pages")

nr_pages equals to number of pages - 1 in perf_mmap. So nr_pages = 0 is
valid.

So the nr_pages != 0 && !is_power_of_2(nr_pages) are all
needed for checking. Otherwise, for example, perf test 6 failed.

 # perf test 6
  6: x86 rdpmc test                                         :Error:
 mmap() syscall returned with (Invalid argument)
 FAILED!

Signed-off-by: Kan Liang <kan.liang@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1425280466-7830-1-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2015-03-02 18:25:38 -03:00
Ingo Molnar
e9e4e44309 Merge tag 'v4.0-rc1' into perf/core, to refresh the tree
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-26 12:24:50 +01:00
Linus Torvalds
a135c717d5 Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus
Pull MIPS updates from Ralf Baechle:
 "This is the main pull request for MIPS:

   - a number of fixes that didn't make the 3.19 release.

   - a number of cleanups.

   - preliminary support for Cavium's Octeon 3 SOCs which feature up to
     48 MIPS64 R3 cores with FPU and hardware virtualization.

   - support for MIPS R6 processors.

     Revision 6 of the MIPS architecture is a major revision of the MIPS
     architecture which does away with many of original sins of the
     architecture such as branch delay slots.  This and other changes in
     R6 require major changes throughout the entire MIPS core
     architecture code and make up for the lion share of this pull
     request.

   - finally some preparatory work for eXtendend Physical Address
     support, which allows support of up to 40 bit of physical address
     space on 32 bit processors"

     [ Ahh, MIPS can't leave the PAE brain damage alone.  It's like
       every CPU architect has to make that mistake, but pee in the snow
       by changing the TLA.  But whether it's called PAE, LPAE or XPA,
       it's horrid crud   - Linus ]

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (114 commits)
  MIPS: sead3: Corrected get_c0_perfcount_int
  MIPS: mm: Remove dead macro definitions
  MIPS: OCTEON: irq: add CIB and other fixes
  MIPS: OCTEON: Don't do acknowledge operations for level triggered irqs.
  MIPS: OCTEON: More OCTEONIII support
  MIPS: OCTEON: Remove setting of processor specific CVMCTL icache bits.
  MIPS: OCTEON: Core-15169 Workaround and general CVMSEG cleanup.
  MIPS: OCTEON: Update octeon-model.h code for new SoCs.
  MIPS: OCTEON: Implement DCache errata workaround for all CN6XXX
  MIPS: OCTEON: Add little-endian support to asm/octeon/octeon.h
  MIPS: OCTEON: Implement the core-16057 workaround
  MIPS: OCTEON: Delete unused COP2 saving code
  MIPS: OCTEON: Use correct instruction to read 64-bit COP0 register
  MIPS: OCTEON: Save and restore CP2 SHA3 state
  MIPS: OCTEON: Fix FP context save.
  MIPS: OCTEON: Save/Restore wider multiply registers in OCTEON III CPUs
  MIPS: boot: Provide more uImage options
  MIPS: Remove unneeded #ifdef __KERNEL__ from asm/processor.h
  MIPS: ip22-gio: Remove legacy suspend/resume support
  mips: pci: Add ifdef around pci_proc_domain
  ...
2015-02-21 19:41:38 -08:00
Linus Torvalds
f3c233d75e Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull ntp fix from Ingo Molnar:
 "An adjtimex interface regression fix for 32-bit systems"

[ A check that was added in a previous commit is really only a concern
  for 64bit systems, but was applied to both 32 and 64bit systems, which
  results in breaking 32bit systems.

  Thus the fix here is to make the check only apply to 64bit systems ]

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  ntp: Fixup adjtimex freq validation on 32-bit systems
2015-02-21 11:05:22 -08:00
Linus Torvalds
10436cf881 Merge branch 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Ingo Molnar:
 "Two fixes: the paravirt spin_unlock() corruption/crash fix, and an
  rtmutex NULL dereference crash fix"

* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/spinlocks/paravirt: Fix memory corruption on unlock
  locking/rtmutex: Avoid a NULL pointer dereference on deadlock
2015-02-21 10:45:03 -08:00
Linus Torvalds
e2defd0271 Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Ingo Molnar:
 "Thiscontains misc fixes: preempt_schedule_common() and io_schedule()
  recursion fixes, sched/dl fixes, a completion_done() revert, two
  sched/rt fixes and a comment update patch"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/rt: Avoid obvious configuration fail
  sched/autogroup: Fix failure to set cpu.rt_runtime_us
  sched/dl: Do update_rq_clock() in yield_task_dl()
  sched: Prevent recursion in io_schedule()
  sched/completion: Serialize completion_done() with complete()
  sched: Fix preempt_schedule_common() triggering tracing recursion
  sched/dl: Prevent enqueue of a sleeping task in dl_task_timer()
  sched: Make dl_task_time() use task_rq_lock()
  sched: Clarify ordering between task_rq_lock() and move_queued_task()
2015-02-21 10:40:02 -08:00
Linus Torvalds
3f4d9925e9 Merge branches 'core-urgent-for-linus' and 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull rcu fix and x86 irq fix from Ingo Molnar:

 - Fix a bug that caused an RCU warning splat.

 - Two x86 irq related fixes: a hotplug crash fix and an ACPI IRQ
   registry fix.

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rcu: Clear need_qs flag to prevent splat

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/irq: Check for valid irq descriptor in check_irq_vectors_for_cpu_disable()
  x86/irq: Fix regression caused by commit b568b8601f
2015-02-21 10:36:06 -08:00
Linus Torvalds
4fbd0a81a0 Merge tag 'for_linux-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb
Pull kgdb/kdb updates from Jason Wessel:
 "KGDB/KDB New:
   - KDB: improved searching
   - No longer enter debug core on panic if panic timeout is set

  KGDB/KDB regressions / cleanups
   - fix pdf doc build errors
   - prevent junk characters on kdb console from printk levels"

* tag 'for_linux-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jwessel/kgdb:
  kgdb, docs: Fix <para> pdfdocs build errors
  debug: prevent entering debug mode on panic/exception.
  kdb: Const qualifier for kdb_getstr's prompt argument
  kdb: Provide forward search at more prompt
  kdb: Fix a prompt management bug when using | grep
  kdb: Remove stack dump when entering kgdb due to NMI
  kdb: Avoid printing KERN_ levels to consoles
  kdb: Fix off by one error in kdb_cpu()
  kdb: fix incorrect counts in KDB summary command output
2015-02-20 15:13:29 -08:00
Colin Cross
5516fd7b92 debug: prevent entering debug mode on panic/exception.
On non-developer devices, kgdb prevents the device from rebooting
after a panic.

Incase of panics and exceptions, to allow the device to reboot, prevent
entering debug mode to avoid getting stuck waiting for the user to
interact with debugger.

To avoid entering the debugger on panic/exception without any extra
configuration, panic_timeout is being used which can be set via
/proc/sys/kernel/panic at run time and CONFIG_PANIC_TIMEOUT sets the
default value.

Setting panic_timeout indicates that the user requested machine to
perform unattended reboot after panic. We dont want to get stuck waiting
for the user input incase of panic.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: kgdb-bugreport@lists.sourceforge.net
Cc: linux-kernel@vger.kernel.org
Cc: Android Kernel Team <kernel-team@android.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Colin Cross <ccross@android.com>
[Kiran: Added context to commit message.
panic_timeout is used instead of break_on_panic and
break_on_exception to honor CONFIG_PANIC_TIMEOUT
Modified the commit as per community feedback]
Signed-off-by: Kiran Raparthy <kiran.kumar@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
2015-02-19 12:39:03 -06:00
Daniel Thompson
32d375f6f2 kdb: Const qualifier for kdb_getstr's prompt argument
All current callers of kdb_getstr() can pass constant pointers via the
prompt argument. This patch adds a const qualification to make explicit
the fact that this is safe.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
2015-02-19 12:39:03 -06:00
Daniel Thompson
fb6daa7520 kdb: Provide forward search at more prompt
Currently kdb allows the output of comamnds to be filtered using the
| grep feature. This is useful but does not permit the output emitted
shortly after a string match to be examined without wading through the
entire unfiltered output of the command. Such a feature is particularly
useful to navigate function traces because these traces often have a
useful trigger string *before* the point of interest.

This patch reuses the existing filtering logic to introduce a simple
forward search to kdb that can be triggered from the more prompt.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
2015-02-19 12:39:03 -06:00
Daniel Thompson
ab08e464a2 kdb: Fix a prompt management bug when using | grep
Currently when the "| grep" feature is used to filter the output of a
command then the prompt is not displayed for the subsequent command.
Likewise any characters typed by the user are also not echoed to the
display. This rather disconcerting problem eventually corrects itself
when the user presses Enter and the kdb_grepping_flag is cleared as
kdb_parse() tries to make sense of whatever they typed.

This patch resolves the problem by moving the clearing of this flag
from the middle of command processing to the beginning.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
2015-02-19 12:39:03 -06:00
Daniel Thompson
5454388113 kdb: Remove stack dump when entering kgdb due to NMI
Issuing a stack dump feels ergonomically wrong when entering due to NMI.

Entering due to NMI is normally a reaction to a user request, either the
NMI button on a server or a "magic knock" on a UART. Therefore the
backtrace behaviour on entry due to NMI should be like SysRq-g (no stack
dump) rather than like oops.

Note also that the stack dump does not offer any information that
cannot be trivial retrieved using the 'bt' command.

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
2015-02-19 12:39:02 -06:00
Daniel Thompson
f7d4ca8bbf kdb: Avoid printing KERN_ levels to consoles
Currently when kdb traps printk messages then the raw log level prefix
(consisting of '\001' followed by a numeral) does not get stripped off
before the message is issued to the various I/O handlers supported by
kdb. This causes annoying visual noise as well as causing problems
grepping for ^. It is also a change of behaviour compared to normal usage
of printk() usage. For example <SysRq>-h ends up with different output to
that of kdb's "sr h".

This patch addresses the problem by stripping log levels from messages
before they are issued to the I/O handlers. printk() which can also
act as an i/o handler in some cases is special cased; if the caller
provided a log level then the prefix will be preserved when sent to
printk().

The addition of non-printable characters to the output of kdb commands is a
regression, albeit and extremely elderly one, introduced by commit
04d2c8c83d ("printk: convert the format for KERN_<LEVEL> to a 2 byte
pattern"). Note also that this patch does *not* restore the original
behaviour from v3.5. Instead it makes printk() from within a kdb command
display the message without any prefix (i.e. like printk() normally does).

Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Joe Perches <joe@perches.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
2015-02-19 12:39:02 -06:00
Jason Wessel
df0036d117 kdb: Fix off by one error in kdb_cpu()
There was a follow on replacement patch against the prior
"kgdb: Timeout if secondary CPUs ignore the roundup".

See: https://lkml.org/lkml/2015/1/7/442

This patch is the delta vs the patch that was committed upstream:
  * Fix an off-by-one error in kdb_cpu().
  * Replace NR_CPUS with CONFIG_NR_CPUS to tell checkpatch that we
    really want a static limit.
  * Removed the "KGDB: " prefix from the pr_crit() in debug_core.c
    (kgdb-next contains a patch which introduced pr_fmt() to this file
    to the tag will now be applied automatically).

Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
2015-02-19 12:39:02 -06:00
Jay Lan
1467559232 kdb: fix incorrect counts in KDB summary command output
The output of KDB 'summary' command should report MemTotal, MemFree
and Buffers output in kB. Current codes report in unit of pages.

A define of K(x) as
is defined in the code, but not used.

This patch would apply the define to convert the values to kB.
Please include me on Cc on replies. I do not subscribe to linux-kernel.

Signed-off-by: Jay Lan <jlan@sgi.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
2015-02-19 12:39:02 -06:00
Linus Torvalds
27a22ee4c7 Merge branch 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild
Pull kbuild updates from Michal Marek:

 - several cleanups in kbuild

 - serialize multiple *config targets so that 'make defconfig kvmconfig'
   works

 - The cc-ifversion macro got support for an else-branch

* 'kbuild' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild:
  kbuild,gcov: simplify kernel/gcov/Makefile more
  kbuild: allow cc-ifversion to have the argument for false condition
  kbuild,gcov: simplify kernel/gcov/Makefile
  kbuild,gcov: remove unnecessary workaround
  kbuild: do not add $(call ...) to invoke cc-version or cc-fullversion
  kbuild: fix cc-ifversion macro
  kbuild: drop $(version_h) from MRPROPER_FILES
  kbuild: use mixed-targets when two or more config targets are given
  kbuild: remove redundant line from bounds.h/asm-offsets.h
  kbuild: merge bounds.h and asm-offsets.h rules
  kbuild: Drop support for clean-rule
2015-02-19 10:07:08 -08:00
Ingo Molnar
8a26ce4e54 Merge tag 'perf-core-for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/core
Pull perf/core improvements and fixes from Arnaldo Carvalho de Melo:

User visible changes:

  - No need to explicitely enable evsels for workload started from perf, let it
    be enabled via perf_event_attr.enable_on_exec, removing some events that take
    place in the 'perf trace' before a workload is really started by it.
    (Arnaldo Carvalho de Melo)

  - Fix to handle optimized not-inlined functions in 'perf probe' (Masami Hiramatsu)

  - Update 'perf probe' man page (Masami Hiramatsu)

  - 'perf trace': Allow mixing with tracepoints and suppressing plain syscalls
    (Arnaldo Carvalho de Melo)

Infrastructure changes:

  - Introduce {trace_seq_do,event_format_}_fprintf functions to allow
    a default tracepoint field list printer to be used in tools that allows
    redirecting output to a file. (Arnaldo Carvalho de Melo)

  - The man page for pthread_attr_set_affinity_np states that _GNU_SOURCE
    must be defined before pthread.h, do it to fix the build in some
    systems (Josh Boyer)

  - Cleanups in 'perf buildid-cache' (Masami Hiramatsu)

  - Fix dso cache test case (Namhyung Kim)

  - Do Not rely on dso__data_read_offset() to open DSO (Namhyung Kim)

  - Make perf aware of tracefs (Steven Rostedt).

  - Fix build by defining STT_GNU_IFUNC for glibc 2.9 and older (Vinson Lee)

  - AArch64 symbol resolution fixes (Victor Kamensky)

  - Kconfig beachhead (Jiri Olsa)

  - Simplify nr_pages validity (Kaixu Xia)

  - Fixup header positioning in 'perf list' (Yunlong Song)

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-18 19:18:18 +01:00
Ingo Molnar
3b3336d4fe Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/urgent
Pull RCU fix from Paul E. McKenney.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-18 17:59:20 +01:00
Yan, Zheng
a46a230001 perf: Simplify the branch stack check
Use event->attr.branch_sample_type to replace
intel_pmu_needs_lbr_smpl() for avoiding duplicated code that
implicitly enables the LBR.

Currently, branch stack can be enabled by user explicitly requesting
branch sampling or implicit branch sampling to correct PEBS skid.

For user explicitly requested branch sampling, the branch_sample_type
is explicitly set by user. For PEBS case, the branch_sample_type is also
implicitly set to PERF_SAMPLE_BRANCH_ANY in x86_pmu_hw_config.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: eranian@google.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/1415156173-10035-11-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-18 17:16:11 +01:00
Yan, Zheng
5a158c3ccd perf: Always switch pmu specific data during context switch
If two tasks were both forked from the same parent task, Events in
their perf task contexts can be the same. Perf core may leave out
switching the perf event contexts.

Previous patch inroduces pmu specific data. The data is for saving
the LBR stack, it is task specific. So we need to switch the data
even when context switch is optimized out.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: eranian@google.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/1415156173-10035-7-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-18 17:16:07 +01:00
Yan, Zheng
4af57ef28c perf: Add pmu specific data for perf task context
Introduce a new flag PERF_ATTACH_TASK_DATA for perf event's attach
stata. The flag is set by PMU's event_init() callback, it indicates
that perf event needs PMU specific data.

The PMU specific data are initialized to zeros. Later patches will
use PMU specific data to save LBR stack.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: eranian@google.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/1415156173-10035-6-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-18 17:16:05 +01:00
Yan, Zheng
2a0ad3b326 perf/x86/intel: Use context switch callback to flush LBR stack
Previous commit introduces context switch callback, its function
overlaps with the flush branch stack callback. So we can use the
context switch callback to flush LBR stack.

This patch adds code that uses the flush branch callback to
flush the LBR stack when task is being scheduled in. The callback
is enabled only when there are events use the LBR hardware. This
patch also removes all old flush branch stack code.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: eranian@google.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/1415156173-10035-4-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-18 17:16:03 +01:00
Yan, Zheng
ba532500c5 perf: Introduce pmu context switch callback
The callback is invoked when process is scheduled in or out.
It provides mechanism for later patches to save/store the LBR
stack. For the schedule in case, the callback is invoked at
the same place that flush branch stack callback is invoked.
So it also can replace the flush branch stack callback. To
avoid unnecessary overhead, the callback is enabled only when
there are events use the LBR stack.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: eranian@google.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/1415156173-10035-3-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-18 17:16:02 +01:00
Shaohua Li
6a694a607a perf: Update userspace page info for software event
For hardware events, the userspace page of the event gets updated in
context switches, so if we read the timestamp in the page, we get
fresh info.

For software events, this is missing currently. This patch makes the
behavior consistent.

With this patch, we can implement clock_gettime(THREAD_CPUTIME) with
PERF_COUNT_SW_DUMMY in userspace as suggested by Andy and Peter. Code
like this:

  if (pc->cap_user_time) {
	do {
		seq = pc->lock;
		barrier();

		running = pc->time_running;
		cyc = rdtsc();
		time_mult = pc->time_mult;
		time_shift = pc->time_shift;
		time_offset = pc->time_offset;

		barrier();
	} while (pc->lock != seq);

	quot = (cyc >> time_shift);
	rem = cyc & ((1 << time_shift) - 1);
	delta = time_offset + quot * time_mult +
		((rem * time_mult) >> time_shift);

	running += delta;
	return running;
  }

I tried it on a busy system, the userspace page updating doesn't
have noticeable overhead.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/aa2dd2e4f1e9f2225758be5ba00f14d6909a8ce1.1423180257.git.shli@fb.com
[ Improved the changelog. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-02-18 17:01:45 +01:00