linux-toradex.git/kernel, branch v3.4.57 Linux kernel for Apalis and Colibri modules perf: Use css_tryget() to avoid propping up css refcount 2013-08-11T22:38:43+00:00 Salman Qazi sqazi@google.com 2012-06-14T22:31:09+00:00 2d8be9cf0668fab848b9b7740f0725ae9181b703 commit 9c5da09d266ca9b32eb16cf940f8161d949c2fe5 upstream. An rmdir pushes css's ref count to zero. However, if the associated directory is open at the time, the dentry ref count is non-zero. If the fd for this directory is then passed into perf_event_open, it does a css_get(). This bounces the ref count back up from zero. This is a problem by itself. But what makes it turn into a crash is the fact that we end up doing an extra dput, since we perform a dput when css_put sees the ref count go down to zero. css_tryget() does not fall into that trap. So, we use that instead. Reproduction test-case for the bug: #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <linux/unistd.h> #include <linux/perf_event.h> #include <string.h> #include <errno.h> #include <stdio.h> #define PERF_FLAG_PID_CGROUP (1U << 2) int perf_event_open(struct perf_event_attr *hw_event_uptr, pid_t pid, int cpu, int group_fd, unsigned long flags) { return syscall(__NR_perf_event_open,hw_event_uptr, pid, cpu, group_fd, flags); } /* * Directly poke at the perf_event bug, since it's proving hard to repro * depending on where in the kernel tree. what moved? */ int main(int argc, char **argv) { int fd; struct perf_event_attr attr; memset(&attr, 0, sizeof(attr)); attr.exclude_kernel = 1; attr.size = sizeof(attr); mkdir("/dev/cgroup/perf_event/blah", 0777); fd = open("/dev/cgroup/perf_event/blah", O_RDONLY); perror("open"); rmdir("/dev/cgroup/perf_event/blah"); sleep(2); perf_event_open(&attr, fd, 0, -1, PERF_FLAG_PID_CGROUP); perror("perf_event_open"); close(fd); return 0; } Signed-off-by: Salman Qazi <sqazi@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/20120614223108.1025.2503.stgit@dungbeetle.mtv.corp.google.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Li Zefan <lizefan@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 9c5da09d266ca9b32eb16cf940f8161d949c2fe5 upstream.

An rmdir pushes css's ref count to zero.  However, if the associated
directory is open at the time, the dentry ref count is non-zero.  If
the fd for this directory is then passed into perf_event_open, it
does a css_get().  This bounces the ref count back up from zero.  This
is a problem by itself.  But what makes it turn into a crash is the
fact that we end up doing an extra dput, since we perform a dput
when css_put sees the ref count go down to zero.

css_tryget() does not fall into that trap. So, we use that instead.

Reproduction test-case for the bug:

 #include <unistd.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <linux/unistd.h>
 #include <linux/perf_event.h>
 #include <string.h>
 #include <errno.h>
 #include <stdio.h>

 #define PERF_FLAG_PID_CGROUP    (1U << 2)

 int perf_event_open(struct perf_event_attr *hw_event_uptr,
                     pid_t pid, int cpu, int group_fd, unsigned long flags) {
         return syscall(__NR_perf_event_open,hw_event_uptr, pid, cpu,
                 group_fd, flags);
 }

 /*
  * Directly poke at the perf_event bug, since it's proving hard to repro
  * depending on where in the kernel tree.  what moved?
  */
 int main(int argc, char **argv)
 {
        int fd;
        struct perf_event_attr attr;
        memset(&attr, 0, sizeof(attr));
        attr.exclude_kernel = 1;
        attr.size = sizeof(attr);
        mkdir("/dev/cgroup/perf_event/blah", 0777);
        fd = open("/dev/cgroup/perf_event/blah", O_RDONLY);
        perror("open");
        rmdir("/dev/cgroup/perf_event/blah");
        sleep(2);
        perf_event_open(&attr, fd, 0, -1,  PERF_FLAG_PID_CGROUP);
        perror("perf_event_open");
        close(fd);
        return 0;
 }

Signed-off-by: Salman Qazi <sqazi@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/20120614223108.1025.2503.stgit@dungbeetle.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
perf: Fix event group context move 2013-08-11T22:38:43+00:00 Jiri Olsa jolsa@redhat.com 2013-02-01T10:23:45+00:00 5cbff87c00cf1b8e3a077465e4ec501dd21651c8 commit 0231bb5336758426b44ccd798ccd3c5419c95d58 upstream. When we have group with mixed events (hw/sw) we want to end up with group leader being in hw context. So if group leader is initialy sw event, we move all the events under hw context. The move is done for each event by removing it from its context and adding it back into proper one. As a part of the removal the event is automatically disabled, which is not what we want at this stage of creating groups. The fix is to initialize event state after removal from sw context. This fix resulted from the following discussion: http://thread.gmane.org/gmane.linux.kernel.perf.user/1144 Reported-by: Andreas Hollmann <hollmann@in.tum.de> Signed-off-by: Jiri Olsa <jolsa@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Stephane Eranian <eranian@google.com> Cc: Vince Weaver <vince@deater.net> Link: http://lkml.kernel.org/r/1359714225-4231-1-git-send-email-jolsa@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Li Zefan <lizefan@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 0231bb5336758426b44ccd798ccd3c5419c95d58 upstream.

When we have group with mixed events (hw/sw) we want to end up
with group leader being in hw context. So if group leader is
initialy sw event, we move all the events under hw context.

The move is done for each event by removing it from its context
and adding it back into proper one. As a part of the removal the
event is automatically disabled, which is not what we want at
this stage of creating groups.

The fix is to initialize event state after removal from sw
context.

This fix resulted from the following discussion:

  http://thread.gmane.org/gmane.linux.kernel.perf.user/1144

Reported-by: Andreas Hollmann <hollmann@in.tum.de>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Cc: Vince Weaver <vince@deater.net>
Link: http://lkml.kernel.org/r/1359714225-4231-1-git-send-email-jolsa@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
sched: Fix the broken sched_rr_get_interval() 2013-08-11T22:38:43+00:00 Zhu Yanhai gaoyang.zyh@taobao.com 2013-01-08T04:56:52+00:00 1836cd176170d39f5b1fda9cd47d3c3f0f10dad2 commit a59f4e079d19464eebb9b06513a1d4f55fdae5ba upstream. The caller of sched_sliced() should pass se.cfs_rq and se as the arguments, however in sched_rr_get_interval() we gave it rq.cfs_rq and se, which made the following computation obviously wrong. The change was introduced by commit: 77034937dc45 sched: fix crash in sys_sched_rr_get_interval() ... 5 years ago, while it had been the correct 'cfs_rq_of' before the commit. The change seems to be irrelevant to the commit msg, which was to return a 0 timeslice for tasks that are on an idle runqueue. So I believe that was just a plain typo. Signed-off-by: Zhu Yanhai <gaoyang.zyh@taobao.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paul Turner <pjt@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/1357621012-15039-1-git-send-email-gaoyang.zyh@taobao.com [ Since this is an ABI and an old bug, we'll test this via a slow upstream route, to hopefully discover any app breakage. ] Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit a59f4e079d19464eebb9b06513a1d4f55fdae5ba upstream.

The caller of sched_sliced() should pass se.cfs_rq and se as the
arguments, however in sched_rr_get_interval() we gave it
rq.cfs_rq and se, which made the following computation obviously
wrong.

The change was introduced by commit:

  77034937dc45 sched: fix crash in sys_sched_rr_get_interval()

... 5 years ago, while it had been the correct 'cfs_rq_of' before
the commit. The change seems to be irrelevant to the commit
msg, which was to return a 0 timeslice for tasks that are on an
idle runqueue. So I believe that was just a plain typo.

Signed-off-by: Zhu Yanhai <gaoyang.zyh@taobao.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Turner <pjt@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1357621012-15039-1-git-send-email-gaoyang.zyh@taobao.com
[ Since this is an ABI and an old bug, we'll test this via a
  slow upstream route, to hopefully discover any app breakage. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tracing: Fix irqs-off tag display in syscall tracing 2013-08-04T08:25:45+00:00 zhangwei(Jovi) jovi.zhangwei@huawei.com 2013-07-29T01:33:58+00:00 352b6418a2d14c754b41f23e0698f0006c914b95 commit 11034ae9c20f4057a6127fc965906417978e69b2 upstream Initialization of variable irq_flags and pc was missed when backport 11034ae9c to linux-3.0.y and linux-3.4.y, my fault. Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 11034ae9c20f4057a6127fc965906417978e69b2 upstream

Initialization of variable irq_flags and pc was missed when backport
11034ae9c to linux-3.0.y and linux-3.4.y, my fault.

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
hrtimers: Move SMP function call to thread context 2013-07-28T23:26:47+00:00 Thomas Gleixner tglx@linutronix.de 2013-07-05T10:09:18+00:00 39367f485b87492a5e51af8496a684eafa4aec86 commit 5ec2481b7b47a4005bb446d176e5d0257400c77d upstream. smp_call_function_* must not be called from softirq context. But clock_was_set() which calls on_each_cpu() is called from softirq context to implement a delayed clock_was_set() for the timer interrupt handler. Though that almost never gets invoked. A recent change in the resume code uses the softirq based delayed clock_was_set to support Xens resume mechanism. linux-next contains a new warning which warns if smp_call_function_* is called from softirq context which gets triggered by that Xen change. Fix this by moving the delayed clock_was_set() call to a work context. Reported-and-tested-by: Artem Savkov <artem.savkov@gmail.com> Reported-by: Sasha Levin <sasha.levin@oracle.com> Cc: David Vrabel <david.vrabel@citrix.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: H. Peter Anvin <hpa@zytor.com>, Cc: Konrad Wilk <konrad.wilk@oracle.com> Cc: John Stultz <john.stultz@linaro.org> Cc: xen-devel@lists.xen.org Cc: stable@vger.kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 5ec2481b7b47a4005bb446d176e5d0257400c77d upstream.

smp_call_function_* must not be called from softirq context.

But clock_was_set() which calls on_each_cpu() is called from softirq
context to implement a delayed clock_was_set() for the timer interrupt
handler. Though that almost never gets invoked. A recent change in the
resume code uses the softirq based delayed clock_was_set to support
Xens resume mechanism.

linux-next contains a new warning which warns if smp_call_function_*
is called from softirq context which gets triggered by that Xen
change.

Fix this by moving the delayed clock_was_set() call to a work context.

Reported-and-tested-by: Artem Savkov <artem.savkov@gmail.com>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>,
Cc: Konrad Wilk <konrad.wilk@oracle.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: xen-devel@lists.xen.org
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tracing: Fix irqs-off tag display in syscall tracing 2013-07-28T23:26:46+00:00 zhangwei(Jovi) jovi.zhangwei@huawei.com 2013-04-10T03:26:23+00:00 f36a0d6764dcb33a280dce206f1be4bcaff5714e commit 11034ae9c20f4057a6127fc965906417978e69b2 upstream. All syscall tracing irqs-off tags are wrong, the syscall enter entry doesn't disable irqs. [root@jovi tracing]#echo "syscalls:sys_enter_open" > set_event [root@jovi tracing]# cat trace # tracer: nop # # entries-in-buffer/entries-written: 13/13 #P:2 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | irqbalance-513 [000] d... 56115.496766: sys_open(filename: 804e1a6, flags: 0, mode: 1b6) irqbalance-513 [000] d... 56115.497008: sys_open(filename: 804e1bb, flags: 0, mode: 1b6) sendmail-771 [000] d... 56115.827982: sys_open(filename: b770e6d1, flags: 0, mode: 1b6) The reason is syscall tracing doesn't record irq_flags into buffer. The proper display is: [root@jovi tracing]#echo "syscalls:sys_enter_open" > set_event [root@jovi tracing]# cat trace # tracer: nop # # entries-in-buffer/entries-written: 14/14 #P:2 # # _-----=> irqs-off # / _----=> need-resched # | / _---=> hardirq/softirq # || / _--=> preempt-depth # ||| / delay # TASK-PID CPU# |||| TIMESTAMP FUNCTION # | | | |||| | | irqbalance-514 [001] .... 46.213921: sys_open(filename: 804e1a6, flags: 0, mode: 1b6) irqbalance-514 [001] .... 46.214160: sys_open(filename: 804e1bb, flags: 0, mode: 1b6) <...>-920 [001] .... 47.307260: sys_open(filename: 4e82a0c5, flags: 80000, mode: 0) Link: http://lkml.kernel.org/r/1365564393-10972-3-git-send-email-jovi.zhangwei@huawei.com Cc: stable@vger.kernel.org # 2.6.35 Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 11034ae9c20f4057a6127fc965906417978e69b2 upstream.

All syscall tracing irqs-off tags are wrong, the syscall enter entry doesn't
disable irqs.

 [root@jovi tracing]#echo "syscalls:sys_enter_open" > set_event
 [root@jovi tracing]# cat trace
 # tracer: nop
 #
 # entries-in-buffer/entries-written: 13/13   #P:2
 #
 #                              _-----=> irqs-off
 #                             / _----=> need-resched
 #                            | / _---=> hardirq/softirq
 #                            || / _--=> preempt-depth
 #                            ||| /     delay
 #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
 #              | |       |   ||||       |         |
       irqbalance-513   [000] d... 56115.496766: sys_open(filename: 804e1a6, flags: 0, mode: 1b6)
       irqbalance-513   [000] d... 56115.497008: sys_open(filename: 804e1bb, flags: 0, mode: 1b6)
         sendmail-771   [000] d... 56115.827982: sys_open(filename: b770e6d1, flags: 0, mode: 1b6)

The reason is syscall tracing doesn't record irq_flags into buffer.
The proper display is:

 [root@jovi tracing]#echo "syscalls:sys_enter_open" > set_event
 [root@jovi tracing]# cat trace
 # tracer: nop
 #
 # entries-in-buffer/entries-written: 14/14   #P:2
 #
 #                              _-----=> irqs-off
 #                             / _----=> need-resched
 #                            | / _---=> hardirq/softirq
 #                            || / _--=> preempt-depth
 #                            ||| /     delay
 #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
 #              | |       |   ||||       |         |
       irqbalance-514   [001] ....    46.213921: sys_open(filename: 804e1a6, flags: 0, mode: 1b6)
       irqbalance-514   [001] ....    46.214160: sys_open(filename: 804e1bb, flags: 0, mode: 1b6)
            <...>-920   [001] ....    47.307260: sys_open(filename: 4e82a0c5, flags: 80000, mode: 0)

Link: http://lkml.kernel.org/r/1365564393-10972-3-git-send-email-jovi.zhangwei@huawei.com

Cc: stable@vger.kernel.org # 2.6.35
Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
perf: Fix perf_lock_task_context() vs RCU 2013-07-28T23:25:48+00:00 Peter Zijlstra peterz@infradead.org 2013-07-12T09:08:33+00:00 41154a356f6516ffa266e50ff7d1bf706893dfe3 commit 058ebd0eba3aff16b144eabf4510ed9510e1416e upstream. Jiri managed to trigger this warning: [] ====================================================== [] [ INFO: possible circular locking dependency detected ] [] 3.10.0+ #228 Tainted: G W [] ------------------------------------------------------- [] p/6613 is trying to acquire lock: [] (rcu_node_0){..-...}, at: [<ffffffff810ca797>] rcu_read_unlock_special+0xa7/0x250 [] [] but task is already holding lock: [] (&ctx->lock){-.-...}, at: [<ffffffff810f2879>] perf_lock_task_context+0xd9/0x2c0 [] [] which lock already depends on the new lock. [] [] the existing dependency chain (in reverse order) is: [] [] -> #4 (&ctx->lock){-.-...}: [] -> #3 (&rq->lock){-.-.-.}: [] -> #2 (&p->pi_lock){-.-.-.}: [] -> #1 (&rnp->nocb_gp_wq[1]){......}: [] -> #0 (rcu_node_0){..-...}: Paul was quick to explain that due to preemptible RCU we cannot call rcu_read_unlock() while holding scheduler (or nested) locks when part of the read side critical section was preemptible. Therefore solve it by making the entire RCU read side non-preemptible. Also pull out the retry from under the non-preempt to play nice with RT. Reported-by: Jiri Olsa <jolsa@redhat.com> Helped-out-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 058ebd0eba3aff16b144eabf4510ed9510e1416e upstream.

Jiri managed to trigger this warning:

 [] ======================================================
 [] [ INFO: possible circular locking dependency detected ]
 [] 3.10.0+ #228 Tainted: G        W
 [] -------------------------------------------------------
 [] p/6613 is trying to acquire lock:
 []  (rcu_node_0){..-...}, at: [<ffffffff810ca797>] rcu_read_unlock_special+0xa7/0x250
 []
 [] but task is already holding lock:
 []  (&ctx->lock){-.-...}, at: [<ffffffff810f2879>] perf_lock_task_context+0xd9/0x2c0
 []
 [] which lock already depends on the new lock.
 []
 [] the existing dependency chain (in reverse order) is:
 []
 [] -> #4 (&ctx->lock){-.-...}:
 [] -> #3 (&rq->lock){-.-.-.}:
 [] -> #2 (&p->pi_lock){-.-.-.}:
 [] -> #1 (&rnp->nocb_gp_wq[1]){......}:
 [] -> #0 (rcu_node_0){..-...}:

Paul was quick to explain that due to preemptible RCU we cannot call
rcu_read_unlock() while holding scheduler (or nested) locks when part
of the read side critical section was preemptible.

Therefore solve it by making the entire RCU read side non-preemptible.

Also pull out the retry from under the non-preempt to play nice with RT.

Reported-by: Jiri Olsa <jolsa@redhat.com>
Helped-out-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
perf: Remove WARN_ON_ONCE() check in __perf_event_enable() for valid scenario 2013-07-28T23:25:48+00:00 Jiri Olsa jolsa@redhat.com 2013-07-09T15:44:11+00:00 1f11f44083bca90ce4f534023658d481b5707d94 commit 06f417968beac6e6b614e17b37d347aa6a6b1d30 upstream. The '!ctx->is_active' check has a valid scenario, so there's no need for the warning. The reason is that there's a time window between the 'ctx->is_active' check in the perf_event_enable() function and the __perf_event_enable() function having: - IRQs on - ctx->lock unlocked where the task could be killed and 'ctx' deactivated by perf_event_exit_task(), ending up with the warning below. So remove the WARN_ON_ONCE() check and add comments to explain it all. This addresses the following warning reported by Vince Weaver: [ 324.983534] ------------[ cut here ]------------ [ 324.984420] WARNING: at kernel/events/core.c:1953 __perf_event_enable+0x187/0x190() [ 324.984420] Modules linked in: [ 324.984420] CPU: 19 PID: 2715 Comm: nmi_bug_snb Not tainted 3.10.0+ #246 [ 324.984420] Hardware name: Supermicro X8DTN/X8DTN, BIOS 4.6.3 01/08/2010 [ 324.984420] 0000000000000009 ffff88043fce3ec8 ffffffff8160ea0b ffff88043fce3f00 [ 324.984420] ffffffff81080ff0 ffff8802314fdc00 ffff880231a8f800 ffff88043fcf7860 [ 324.984420] 0000000000000286 ffff880231a8f800 ffff88043fce3f10 ffffffff8108103a [ 324.984420] Call Trace: [ 324.984420] <IRQ> [<ffffffff8160ea0b>] dump_stack+0x19/0x1b [ 324.984420] [<ffffffff81080ff0>] warn_slowpath_common+0x70/0xa0 [ 324.984420] [<ffffffff8108103a>] warn_slowpath_null+0x1a/0x20 [ 324.984420] [<ffffffff81134437>] __perf_event_enable+0x187/0x190 [ 324.984420] [<ffffffff81130030>] remote_function+0x40/0x50 [ 324.984420] [<ffffffff810e51de>] generic_smp_call_function_single_interrupt+0xbe/0x130 [ 324.984420] [<ffffffff81066a47>] smp_call_function_single_interrupt+0x27/0x40 [ 324.984420] [<ffffffff8161fd2f>] call_function_single_interrupt+0x6f/0x80 [ 324.984420] <EOI> [<ffffffff816161a1>] ? _raw_spin_unlock_irqrestore+0x41/0x70 [ 324.984420] [<ffffffff8113799d>] perf_event_exit_task+0x14d/0x210 [ 324.984420] [<ffffffff810acd04>] ? switch_task_namespaces+0x24/0x60 [ 324.984420] [<ffffffff81086946>] do_exit+0x2b6/0xa40 [ 324.984420] [<ffffffff8161615c>] ? _raw_spin_unlock_irq+0x2c/0x30 [ 324.984420] [<ffffffff81087279>] do_group_exit+0x49/0xc0 [ 324.984420] [<ffffffff81096854>] get_signal_to_deliver+0x254/0x620 [ 324.984420] [<ffffffff81043057>] do_signal+0x57/0x5a0 [ 324.984420] [<ffffffff8161a164>] ? __do_page_fault+0x2a4/0x4e0 [ 324.984420] [<ffffffff8161665c>] ? retint_restore_args+0xe/0xe [ 324.984420] [<ffffffff816166cd>] ? retint_signal+0x11/0x84 [ 324.984420] [<ffffffff81043605>] do_notify_resume+0x65/0x80 [ 324.984420] [<ffffffff81616702>] retint_signal+0x46/0x84 [ 324.984420] ---[ end trace 442ec2f04db3771a ]--- Reported-by: Vince Weaver <vincent.weaver@maine.edu> Signed-off-by: Jiri Olsa <jolsa@redhat.com> Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1373384651-6109-2-git-send-email-jolsa@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 06f417968beac6e6b614e17b37d347aa6a6b1d30 upstream.

The '!ctx->is_active' check has a valid scenario, so
there's no need for the warning.

The reason is that there's a time window between the
'ctx->is_active' check in the perf_event_enable() function
and the __perf_event_enable() function having:

  - IRQs on
  - ctx->lock unlocked

where the task could be killed and 'ctx' deactivated by
perf_event_exit_task(), ending up with the warning below.

So remove the WARN_ON_ONCE() check and add comments to
explain it all.

This addresses the following warning reported by Vince Weaver:

[  324.983534] ------------[ cut here ]------------
[  324.984420] WARNING: at kernel/events/core.c:1953 __perf_event_enable+0x187/0x190()
[  324.984420] Modules linked in:
[  324.984420] CPU: 19 PID: 2715 Comm: nmi_bug_snb Not tainted 3.10.0+ #246
[  324.984420] Hardware name: Supermicro X8DTN/X8DTN, BIOS 4.6.3 01/08/2010
[  324.984420]  0000000000000009 ffff88043fce3ec8 ffffffff8160ea0b ffff88043fce3f00
[  324.984420]  ffffffff81080ff0 ffff8802314fdc00 ffff880231a8f800 ffff88043fcf7860
[  324.984420]  0000000000000286 ffff880231a8f800 ffff88043fce3f10 ffffffff8108103a
[  324.984420] Call Trace:
[  324.984420]  <IRQ>  [<ffffffff8160ea0b>] dump_stack+0x19/0x1b
[  324.984420]  [<ffffffff81080ff0>] warn_slowpath_common+0x70/0xa0
[  324.984420]  [<ffffffff8108103a>] warn_slowpath_null+0x1a/0x20
[  324.984420]  [<ffffffff81134437>] __perf_event_enable+0x187/0x190
[  324.984420]  [<ffffffff81130030>] remote_function+0x40/0x50
[  324.984420]  [<ffffffff810e51de>] generic_smp_call_function_single_interrupt+0xbe/0x130
[  324.984420]  [<ffffffff81066a47>] smp_call_function_single_interrupt+0x27/0x40
[  324.984420]  [<ffffffff8161fd2f>] call_function_single_interrupt+0x6f/0x80
[  324.984420]  <EOI>  [<ffffffff816161a1>] ? _raw_spin_unlock_irqrestore+0x41/0x70
[  324.984420]  [<ffffffff8113799d>] perf_event_exit_task+0x14d/0x210
[  324.984420]  [<ffffffff810acd04>] ? switch_task_namespaces+0x24/0x60
[  324.984420]  [<ffffffff81086946>] do_exit+0x2b6/0xa40
[  324.984420]  [<ffffffff8161615c>] ? _raw_spin_unlock_irq+0x2c/0x30
[  324.984420]  [<ffffffff81087279>] do_group_exit+0x49/0xc0
[  324.984420]  [<ffffffff81096854>] get_signal_to_deliver+0x254/0x620
[  324.984420]  [<ffffffff81043057>] do_signal+0x57/0x5a0
[  324.984420]  [<ffffffff8161a164>] ? __do_page_fault+0x2a4/0x4e0
[  324.984420]  [<ffffffff8161665c>] ? retint_restore_args+0xe/0xe
[  324.984420]  [<ffffffff816166cd>] ? retint_signal+0x11/0x84
[  324.984420]  [<ffffffff81043605>] do_notify_resume+0x65/0x80
[  324.984420]  [<ffffffff81616702>] retint_signal+0x46/0x84
[  324.984420] ---[ end trace 442ec2f04db3771a ]---

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Suggested-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1373384651-6109-2-git-send-email-jolsa@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
perf: Clone child context from parent context pmu 2013-07-28T23:25:48+00:00 Jiri Olsa jolsa@redhat.com 2013-07-09T15:44:10+00:00 c4c6a6ea3adbe790d81ef72f623e22591704fdb9 commit 734df5ab549ca44f40de0f07af1c8803856dfb18 upstream. Currently when the child context for inherited events is created, it's based on the pmu object of the first event of the parent context. This is wrong for the following scenario: - HW context having HW and SW event - HW event got removed (closed) - SW event stays in HW context as the only event and its pmu is used to clone the child context The issue starts when the cpu context object is touched based on the pmu context object (__get_cpu_context). In this case the HW context will work with SW cpu context ending up with following WARN below. Fixing this by using parent context pmu object to clone from child context. Addresses the following warning reported by Vince Weaver: [ 2716.472065] ------------[ cut here ]------------ [ 2716.476035] WARNING: at kernel/events/core.c:2122 task_ctx_sched_out+0x3c/0x) [ 2716.476035] Modules linked in: nfsd auth_rpcgss oid_registry nfs_acl nfs locn [ 2716.476035] CPU: 0 PID: 3164 Comm: perf_fuzzer Not tainted 3.10.0-rc4 #2 [ 2716.476035] Hardware name: AOpen DE7000/nMCP7ALPx-DE R1.06 Oct.19.2012, BI2 [ 2716.476035] 0000000000000000 ffffffff8102e215 0000000000000000 ffff88011fc18 [ 2716.476035] ffff8801175557f0 0000000000000000 ffff880119fda88c ffffffff810ad [ 2716.476035] ffff880119fda880 ffffffff810af02a 0000000000000009 ffff880117550 [ 2716.476035] Call Trace: [ 2716.476035] [<ffffffff8102e215>] ? warn_slowpath_common+0x5b/0x70 [ 2716.476035] [<ffffffff810ab2bd>] ? task_ctx_sched_out+0x3c/0x5f [ 2716.476035] [<ffffffff810af02a>] ? perf_event_exit_task+0xbf/0x194 [ 2716.476035] [<ffffffff81032a37>] ? do_exit+0x3e7/0x90c [ 2716.476035] [<ffffffff810cd5ab>] ? __do_fault+0x359/0x394 [ 2716.476035] [<ffffffff81032fe6>] ? do_group_exit+0x66/0x98 [ 2716.476035] [<ffffffff8103dbcd>] ? get_signal_to_deliver+0x479/0x4ad [ 2716.476035] [<ffffffff810ac05c>] ? __perf_event_task_sched_out+0x230/0x2d1 [ 2716.476035] [<ffffffff8100205d>] ? do_signal+0x3c/0x432 [ 2716.476035] [<ffffffff810abbf9>] ? ctx_sched_in+0x43/0x141 [ 2716.476035] [<ffffffff810ac2ca>] ? perf_event_context_sched_in+0x7a/0x90 [ 2716.476035] [<ffffffff810ac311>] ? __perf_event_task_sched_in+0x31/0x118 [ 2716.476035] [<ffffffff81050dd9>] ? mmdrop+0xd/0x1c [ 2716.476035] [<ffffffff81051a39>] ? finish_task_switch+0x7d/0xa6 [ 2716.476035] [<ffffffff81002473>] ? do_notify_resume+0x20/0x5d [ 2716.476035] [<ffffffff813654f5>] ? retint_signal+0x3d/0x78 [ 2716.476035] ---[ end trace 827178d8a5966c3d ]--- Reported-by: Vince Weaver <vincent.weaver@maine.edu> Signed-off-by: Jiri Olsa <jolsa@redhat.com> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1373384651-6109-1-git-send-email-jolsa@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 734df5ab549ca44f40de0f07af1c8803856dfb18 upstream.

Currently when the child context for inherited events is
created, it's based on the pmu object of the first event
of the parent context.

This is wrong for the following scenario:

  - HW context having HW and SW event
  - HW event got removed (closed)
  - SW event stays in HW context as the only event
    and its pmu is used to clone the child context

The issue starts when the cpu context object is touched
based on the pmu context object (__get_cpu_context). In
this case the HW context will work with SW cpu context
ending up with following WARN below.

Fixing this by using parent context pmu object to clone
from child context.

Addresses the following warning reported by Vince Weaver:

[ 2716.472065] ------------[ cut here ]------------
[ 2716.476035] WARNING: at kernel/events/core.c:2122 task_ctx_sched_out+0x3c/0x)
[ 2716.476035] Modules linked in: nfsd auth_rpcgss oid_registry nfs_acl nfs locn
[ 2716.476035] CPU: 0 PID: 3164 Comm: perf_fuzzer Not tainted 3.10.0-rc4 #2
[ 2716.476035] Hardware name: AOpen   DE7000/nMCP7ALPx-DE R1.06 Oct.19.2012, BI2
[ 2716.476035]  0000000000000000 ffffffff8102e215 0000000000000000 ffff88011fc18
[ 2716.476035]  ffff8801175557f0 0000000000000000 ffff880119fda88c ffffffff810ad
[ 2716.476035]  ffff880119fda880 ffffffff810af02a 0000000000000009 ffff880117550
[ 2716.476035] Call Trace:
[ 2716.476035]  [<ffffffff8102e215>] ? warn_slowpath_common+0x5b/0x70
[ 2716.476035]  [<ffffffff810ab2bd>] ? task_ctx_sched_out+0x3c/0x5f
[ 2716.476035]  [<ffffffff810af02a>] ? perf_event_exit_task+0xbf/0x194
[ 2716.476035]  [<ffffffff81032a37>] ? do_exit+0x3e7/0x90c
[ 2716.476035]  [<ffffffff810cd5ab>] ? __do_fault+0x359/0x394
[ 2716.476035]  [<ffffffff81032fe6>] ? do_group_exit+0x66/0x98
[ 2716.476035]  [<ffffffff8103dbcd>] ? get_signal_to_deliver+0x479/0x4ad
[ 2716.476035]  [<ffffffff810ac05c>] ? __perf_event_task_sched_out+0x230/0x2d1
[ 2716.476035]  [<ffffffff8100205d>] ? do_signal+0x3c/0x432
[ 2716.476035]  [<ffffffff810abbf9>] ? ctx_sched_in+0x43/0x141
[ 2716.476035]  [<ffffffff810ac2ca>] ? perf_event_context_sched_in+0x7a/0x90
[ 2716.476035]  [<ffffffff810ac311>] ? __perf_event_task_sched_in+0x31/0x118
[ 2716.476035]  [<ffffffff81050dd9>] ? mmdrop+0xd/0x1c
[ 2716.476035]  [<ffffffff81051a39>] ? finish_task_switch+0x7d/0xa6
[ 2716.476035]  [<ffffffff81002473>] ? do_notify_resume+0x20/0x5d
[ 2716.476035]  [<ffffffff813654f5>] ? retint_signal+0x3d/0x78
[ 2716.476035] ---[ end trace 827178d8a5966c3d ]---

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1373384651-6109-1-git-send-email-jolsa@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
tracing: Use current_uid() for critical time tracing 2013-07-28T23:25:47+00:00 Steven Rostedt (Red Hat) rostedt@goodmis.org 2013-05-31T01:10:37+00:00 d018274f859ae2cfbe86646948b65a4edd0d335f commit f17a5194859a82afe4164e938b92035b86c55794 upstream. The irqsoff tracer records the max time that interrupts are disabled. There are hooks in the assembly code that calls back into the tracer when interrupts are disabled or enabled. When they are enabled, the tracer checks if the amount of time they were disabled is larger than the previous recorded max interrupts off time. If it is, it creates a snapshot of the currently running trace to store where the last largest interrupts off time was held and how it happened. During testing, this RCU lockdep dump appeared: [ 1257.829021] =============================== [ 1257.829021] [ INFO: suspicious RCU usage. ] [ 1257.829021] 3.10.0-rc1-test+ #171 Tainted: G W [ 1257.829021] ------------------------------- [ 1257.829021] /home/rostedt/work/git/linux-trace.git/include/linux/rcupdate.h:780 rcu_read_lock() used illegally while idle! [ 1257.829021] [ 1257.829021] other info that might help us debug this: [ 1257.829021] [ 1257.829021] [ 1257.829021] RCU used illegally from idle CPU! [ 1257.829021] rcu_scheduler_active = 1, debug_locks = 0 [ 1257.829021] RCU used illegally from extended quiescent state! [ 1257.829021] 2 locks held by trace-cmd/4831: [ 1257.829021] #0: (max_trace_lock){......}, at: [<ffffffff810e2b77>] stop_critical_timing+0x1a3/0x209 [ 1257.829021] #1: (rcu_read_lock){.+.+..}, at: [<ffffffff810dae5a>] __update_max_tr+0x88/0x1ee [ 1257.829021] [ 1257.829021] stack backtrace: [ 1257.829021] CPU: 3 PID: 4831 Comm: trace-cmd Tainted: G W 3.10.0-rc1-test+ #171 [ 1257.829021] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./To be filled by O.E.M., BIOS SDBLI944.86P 05/08/2007 [ 1257.829021] 0000000000000001 ffff880065f49da8 ffffffff8153dd2b ffff880065f49dd8 [ 1257.829021] ffffffff81092a00 ffff88006bd78680 ffff88007add7500 0000000000000003 [ 1257.829021] ffff88006bd78680 ffff880065f49e18 ffffffff810daebf ffffffff810dae5a [ 1257.829021] Call Trace: [ 1257.829021] [<ffffffff8153dd2b>] dump_stack+0x19/0x1b [ 1257.829021] [<ffffffff81092a00>] lockdep_rcu_suspicious+0x109/0x112 [ 1257.829021] [<ffffffff810daebf>] __update_max_tr+0xed/0x1ee [ 1257.829021] [<ffffffff810dae5a>] ? __update_max_tr+0x88/0x1ee [ 1257.829021] [<ffffffff811002b9>] ? user_enter+0xfd/0x107 [ 1257.829021] [<ffffffff810dbf85>] update_max_tr_single+0x11d/0x12d [ 1257.829021] [<ffffffff811002b9>] ? user_enter+0xfd/0x107 [ 1257.829021] [<ffffffff810e2b15>] stop_critical_timing+0x141/0x209 [ 1257.829021] [<ffffffff8109569a>] ? trace_hardirqs_on+0xd/0xf [ 1257.829021] [<ffffffff811002b9>] ? user_enter+0xfd/0x107 [ 1257.829021] [<ffffffff810e3057>] time_hardirqs_on+0x2a/0x2f [ 1257.829021] [<ffffffff811002b9>] ? user_enter+0xfd/0x107 [ 1257.829021] [<ffffffff8109550c>] trace_hardirqs_on_caller+0x16/0x197 [ 1257.829021] [<ffffffff8109569a>] trace_hardirqs_on+0xd/0xf [ 1257.829021] [<ffffffff811002b9>] user_enter+0xfd/0x107 [ 1257.829021] [<ffffffff810029b4>] do_notify_resume+0x92/0x97 [ 1257.829021] [<ffffffff8154bdca>] int_signal+0x12/0x17 What happened was entering into the user code, the interrupts were enabled and a max interrupts off was recorded. The trace buffer was saved along with various information about the task: comm, pid, uid, priority, etc. The uid is recorded with task_uid(tsk). But this is a macro that uses rcu_read_lock() to retrieve the data, and this happened to happen where RCU is blind (user_enter). As only the preempt and irqs off tracers can have this happen, and they both only have the tsk == current, if tsk == current, use current_uid() instead of task_uid(), as current_uid() does not use RCU as only current can change its uid. This fixes the RCU suspicious splat. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit f17a5194859a82afe4164e938b92035b86c55794 upstream.

The irqsoff tracer records the max time that interrupts are disabled.
There are hooks in the assembly code that calls back into the tracer when
interrupts are disabled or enabled.

When they are enabled, the tracer checks if the amount of time they
were disabled is larger than the previous recorded max interrupts off
time. If it is, it creates a snapshot of the currently running trace
to store where the last largest interrupts off time was held and how
it happened.

During testing, this RCU lockdep dump appeared:

[ 1257.829021] ===============================
[ 1257.829021] [ INFO: suspicious RCU usage. ]
[ 1257.829021] 3.10.0-rc1-test+ #171 Tainted: G        W
[ 1257.829021] -------------------------------
[ 1257.829021] /home/rostedt/work/git/linux-trace.git/include/linux/rcupdate.h:780 rcu_read_lock() used illegally while idle!
[ 1257.829021]
[ 1257.829021] other info that might help us debug this:
[ 1257.829021]
[ 1257.829021]
[ 1257.829021] RCU used illegally from idle CPU!
[ 1257.829021] rcu_scheduler_active = 1, debug_locks = 0
[ 1257.829021] RCU used illegally from extended quiescent state!
[ 1257.829021] 2 locks held by trace-cmd/4831:
[ 1257.829021]  #0:  (max_trace_lock){......}, at: [<ffffffff810e2b77>] stop_critical_timing+0x1a3/0x209
[ 1257.829021]  #1:  (rcu_read_lock){.+.+..}, at: [<ffffffff810dae5a>] __update_max_tr+0x88/0x1ee
[ 1257.829021]
[ 1257.829021] stack backtrace:
[ 1257.829021] CPU: 3 PID: 4831 Comm: trace-cmd Tainted: G        W    3.10.0-rc1-test+ #171
[ 1257.829021] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./To be filled by O.E.M., BIOS SDBLI944.86P 05/08/2007
[ 1257.829021]  0000000000000001 ffff880065f49da8 ffffffff8153dd2b ffff880065f49dd8
[ 1257.829021]  ffffffff81092a00 ffff88006bd78680 ffff88007add7500 0000000000000003
[ 1257.829021]  ffff88006bd78680 ffff880065f49e18 ffffffff810daebf ffffffff810dae5a
[ 1257.829021] Call Trace:
[ 1257.829021]  [<ffffffff8153dd2b>] dump_stack+0x19/0x1b
[ 1257.829021]  [<ffffffff81092a00>] lockdep_rcu_suspicious+0x109/0x112
[ 1257.829021]  [<ffffffff810daebf>] __update_max_tr+0xed/0x1ee
[ 1257.829021]  [<ffffffff810dae5a>] ? __update_max_tr+0x88/0x1ee
[ 1257.829021]  [<ffffffff811002b9>] ? user_enter+0xfd/0x107
[ 1257.829021]  [<ffffffff810dbf85>] update_max_tr_single+0x11d/0x12d
[ 1257.829021]  [<ffffffff811002b9>] ? user_enter+0xfd/0x107
[ 1257.829021]  [<ffffffff810e2b15>] stop_critical_timing+0x141/0x209
[ 1257.829021]  [<ffffffff8109569a>] ? trace_hardirqs_on+0xd/0xf
[ 1257.829021]  [<ffffffff811002b9>] ? user_enter+0xfd/0x107
[ 1257.829021]  [<ffffffff810e3057>] time_hardirqs_on+0x2a/0x2f
[ 1257.829021]  [<ffffffff811002b9>] ? user_enter+0xfd/0x107
[ 1257.829021]  [<ffffffff8109550c>] trace_hardirqs_on_caller+0x16/0x197
[ 1257.829021]  [<ffffffff8109569a>] trace_hardirqs_on+0xd/0xf
[ 1257.829021]  [<ffffffff811002b9>] user_enter+0xfd/0x107
[ 1257.829021]  [<ffffffff810029b4>] do_notify_resume+0x92/0x97
[ 1257.829021]  [<ffffffff8154bdca>] int_signal+0x12/0x17

What happened was entering into the user code, the interrupts were enabled
and a max interrupts off was recorded. The trace buffer was saved along with
various information about the task: comm, pid, uid, priority, etc.

The uid is recorded with task_uid(tsk). But this is a macro that uses rcu_read_lock()
to retrieve the data, and this happened to happen where RCU is blind (user_enter).

As only the preempt and irqs off tracers can have this happen, and they both
only have the tsk == current, if tsk == current, use current_uid() instead of
task_uid(), as current_uid() does not use RCU as only current can change its uid.

This fixes the RCU suspicious splat.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>