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Steven Rostedt (VMware) 78f7a45dac ring-buffer: Have ring_buffer_iter_empty() return true when empty 
I noticed that reading the snapshot file when it is empty no longer gives a
status. It suppose to show the status of the snapshot buffer as well as how
to allocate and use it. For example:

 ># cat snapshot
 # tracer: nop
 #
 #
 # * Snapshot is allocated *
 #
 # Snapshot commands:
 # echo 0 > snapshot : Clears and frees snapshot buffer
 # echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.
 #                      Takes a snapshot of the main buffer.
 # echo 2 > snapshot : Clears snapshot buffer (but does not allocate or free)
 #                      (Doesn't have to be '2' works with any number that
 #                       is not a '0' or '1')

But instead it just showed an empty buffer:

 ># cat snapshot
 # tracer: nop
 #
 # entries-in-buffer/entries-written: 0/0   #P:4
 #
 #                              _-----=> irqs-off
 #                             / _----=> need-resched
 #                            | / _---=> hardirq/softirq
 #                            || / _--=> preempt-depth
 #                            ||| /     delay
 #           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
 #              | |       |   ||||       |         |

What happened was that it was using the ring_buffer_iter_empty() function to
see if it was empty, and if it was, it showed the status. But that function
was returning false when it was empty. The reason was that the iter header
page was on the reader page, and the reader page was empty, but so was the
buffer itself. The check only tested to see if the iter was on the commit
page, but the commit page was no longer pointing to the reader page, but as
all pages were empty, the buffer is also.

Cc: stable@vger.kernel.org
Fixes: 651e22f270 ("ring-buffer: Always reset iterator to reader page")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2017-04-19 21:23:47 -04:00
..
bpf bpf: fix hashmap extra_elems logic 2017-03-22 14:12:18 -07:00
cgroup Merge branch 'for-4.11-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2017-03-14 15:11:19 -07:00
configs config: android-base: enable hardened usercopy and kernel ASLR 2017-02-27 18:43:46 -08:00
debug sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h> 2017-03-02 08:42:34 +01:00
events Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-17 13:59:52 -07:00
gcov
irq sched/headers: Prepare to move the get_task_struct()/put_task_struct() and related APIs from <linux/sched.h> to <linux/sched/task.h> 2017-03-02 08:42:40 +01:00
livepatch livepatch/module: make TAINT_LIVEPATCH module-specific 2016-08-26 14:42:08 +02:00
locking locking/rwsem: Fix down_write_killable() for CONFIG_RWSEM_GENERIC_SPINLOCK=y 2017-03-16 09:28:30 +01:00
power Merge branch 'WIP.sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-03 10:16:38 -08:00
printk sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task_stack.h> 2017-03-02 08:42:36 +01:00
rcu sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h> 2017-03-02 08:42:34 +01:00
sched Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-04-02 09:25:10 -07:00
time Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-03-07 14:45:22 -08:00
trace ring-buffer: Have ring_buffer_iter_empty() return true when empty 2017-04-19 21:23:47 -04:00
.gitignore
acct.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
async.c
audit.c audit: fix auditd/kernel connection state tracking 2017-03-21 11:26:35 -04:00
audit.h audit: fix auditd/kernel connection state tracking 2017-03-21 11:26:35 -04:00
audit_fsnotify.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-12-17 18:44:00 -08:00
audit_tree.c Merge branch 'stable-4.10' of git://git.infradead.org/users/pcmoore/audit 2017-01-05 23:06:06 -08:00
audit_watch.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-12-17 18:44:00 -08:00
auditfilter.c audit: add support for session ID user filter 2016-11-29 15:10:12 -05:00
auditsc.c audit: fix auditd/kernel connection state tracking 2017-03-21 11:26:35 -04:00
backtracetest.c
bounds.c
capability.c capability: export has_capability 2017-01-12 07:01:56 -07:00
compat.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
configs.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
context_tracking.c
cpu.c cpu/hotplug: Serialize callback invocations proper 2017-03-14 19:19:27 +01:00
cpu_pm.c
crash_dump.c
cred.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/coredump.h> 2017-03-02 08:42:28 +01:00
delayacct.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
dma.c
elfcore.c
exec_domain.c
exit.c userfaultfd: non-cooperative: rollback userfaultfd_exit 2017-03-09 17:01:09 -08:00
extable.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2017-02-22 10:15:09 -08:00
fork.c sched/headers, RCU: Move rcu_copy_process() from <linux/sched/task.h> to kernel/fork.c 2017-03-03 01:43:46 +01:00
freezer.c
futex.c futex: Add missing error handling to FUTEX_REQUEUE_PI 2017-03-14 21:45:36 +01:00
futex_compat.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
groups.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
hung_task.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h> 2017-03-02 08:42:34 +01:00
irq_work.c
jump_label.c This release has no new tracing features, just clean ups, minor fixes 2017-02-27 13:26:17 -08:00
kallsyms.c bpf: make jited programs visible in traces 2017-02-17 13:40:05 -05:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks locking/mutex: Allow MUTEX_SPIN_ON_OWNER when DEBUG_MUTEXES 2016-10-25 11:31:51 +02:00
Kconfig.preempt
kcov.c kcov: make kcov work properly with KASLR enabled 2016-12-20 09:48:47 -08:00
kexec.c
kexec_core.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk 2017-02-22 17:33:34 -08:00
kexec_file.c kexec, x86/purgatory: Unbreak it and clean it up 2017-03-10 20:55:09 +01:00
kexec_internal.h kexec, x86/purgatory: Unbreak it and clean it up 2017-03-10 20:55:09 +01:00
kmod.c sched/headers, vfs/execve: Prepare to move the do_execve*() prototypes from <linux/sched.h> to <linux/binfmts.h> 2017-03-02 08:42:39 +01:00
kprobes.c powerpc updates for 4.11 part 1. 2017-02-22 10:30:38 -08:00
ksysfs.c kernel/ksysfs.c: add __ro_after_init to bin_attribute structure 2017-02-24 17:46:56 -08:00
kthread.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h> 2017-03-02 08:42:35 +01:00
latencytop.c sched/headers: Prepare to move sched_info_on() and force_schedstat_enabled() from <linux/sched.h> to <linux/sched/stat.h> 2017-03-02 08:42:39 +01:00
Makefile cgroup: move cgroup files under kernel/cgroup/ 2016-12-27 14:49:05 -05:00
membarrier.c Fix: Disable sys_membarrier when nohz_full is enabled 2017-01-23 11:32:16 -08:00
memremap.c mm: add private lock to serialize memory hotplug operations 2017-03-16 16:56:18 -07:00
module-internal.h
module.c Modules updates for v4.11 2017-02-22 17:08:33 -08:00
module_signing.c
notifier.c kernel/notifier.c: simplify expression 2017-02-24 17:46:56 -08:00
nsproxy.c
padata.c padata: avoid race in reordering 2017-03-24 21:51:33 +08:00
panic.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h> 2017-03-02 08:42:34 +01:00
params.c
pid.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h> 2017-03-02 08:42:35 +01:00
pid_namespace.c sched/headers: Prepare for the reduction of <linux/sched.h>'s signal API dependency 2017-03-02 08:42:37 +01:00
profile.c sched/headers: Prepare to move sched_info_on() and force_schedstat_enabled() from <linux/sched.h> to <linux/sched/stat.h> 2017-03-02 08:42:39 +01:00
ptrace.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h> 2017-03-02 08:42:35 +01:00
range.c
reboot.c
relay.c lib/vsprintf.c: remove %Z support 2017-02-27 18:43:47 -08:00
resource.c
seccomp.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task_stack.h> 2017-03-02 08:42:36 +01:00
signal.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
smp.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/idle.h> 2017-03-02 08:42:26 +01:00
smpboot.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h> 2017-03-02 08:42:35 +01:00
smpboot.h
softirq.c softirq: Display IRQ_POLL for irq-poll statistics 2016-10-21 15:45:47 -06:00
stacktrace.c stacktrace, lockdep: Fix address, newline ugliness 2017-02-08 08:21:31 +01:00
stop_machine.c locking/core, stop_machine: Yield the CPU during stop machine() 2016-11-16 10:15:09 +01:00
sys.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
sys_ni.c move aio compat to fs/aio.c 2016-12-22 22:58:37 -05:00
sysctl.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/coredump.h> 2017-03-02 08:42:28 +01:00
sysctl_binary.c sysctl: add KERN_CONT to deprecated_sysctl_warning() 2016-12-14 16:04:07 -08:00
task_work.c
taskstats.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-11-15 10:54:36 -05:00
test_kprobes.c
torture.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/clock.h> 2017-03-02 08:42:27 +01:00
tracepoint.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h> 2017-03-02 08:42:35 +01:00
tsacct.c sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h> 2017-03-02 08:42:39 +01:00
ucount.c ucount: Remove the atomicity from ucount->count 2017-03-06 15:26:37 -06:00
uid16.c sched/headers: Prepare to remove <linux/cred.h> inclusion from <linux/sched.h> 2017-03-02 08:42:31 +01:00
up.c smp: Add function to execute a function synchronously on a CPU 2016-09-05 13:52:39 +02:00
user-return-notifier.c
user.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/user.h> 2017-03-02 08:42:29 +01:00
user_namespace.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/signal.h> 2017-03-02 08:42:29 +01:00
utsname.c sched/headers: Prepare to move the task_lock()/unlock() APIs to <linux/sched/task.h> 2017-03-02 08:42:38 +01:00
utsname_sysctl.c sched/headers: Remove <linux/rwsem.h> from <linux/sched.h> 2017-03-03 01:45:36 +01:00
watchdog.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h> 2017-03-02 08:42:34 +01:00
watchdog_hld.c sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h> 2017-03-02 08:42:34 +01:00
workqueue.c workqueue: trigger WARN if queue_delayed_work() is called with NULL @wq 2017-03-06 15:33:42 -05:00
workqueue_internal.h