register_stat_tracer() uses list_for_each_entry_safe
to check whether a tracer is already present in the list.
But we don't delete anything from the list here, so
we don't need the safe version
[ Impact: cleanup list use is stat tracing ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
- remove duplicate code in stat_seq_init()
- update comments to reflect the change from stat list to stat rbtree
[ Impact: clean up ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
When closing a trace_stat file, we destroy the rbtree constructed during
file open, but there is memory leak that the root node is not freed.
[ Impact: fix memory leak when closing a trace_stat file ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Currently the output of trace_stat/workqueues is totally reversed:
# cat /debug/tracing/trace_stat/workqueues
...
1 17 17 210 37 `-blk_unplug_work+0x0/0x57
1 3779 3779 181 11 |-cfq_kick_queue+0x0/0x2f
1 3796 3796 kblockd/1:120
...
The correct output should be:
1 3796 3796 kblockd/1:120
1 3779 3779 181 11 |-cfq_kick_queue+0x0/0x2f
1 17 17 210 37 `-blk_unplug_work+0x0/0x57
It's caused by "tracing/stat: replace linked list by an rbtree for
sorting"
(53059c9b67a62a3dc8c80204d3da42b9267ea5a0).
dummpy_cmp() should return -1, so rb_node will always be inserted as
right-most node in the rbtree, thus we sort the output in ascending
order.
[ Impact: fix the output of trace_stat/workqueues ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
When the stat tracing framework prepares the entries from a tracer
to output them to the user, it starts by computing a linear sort
through a linked list to give the entries ordered by relevance
to the user.
This is quite ugly and causes a small latency when we begin to
read the file.
This patch changes that by turning the linked list into a red-black
tree. Athough the whole iteration using the start and next tracer
callbacks while opening the file remain the same, it is now much
more fast and scalable.
The rbtree guarantees O(log(n)) insertions whereas a linked
list with linear sorting brought us a O(n) despair. Now the
(visible) latency has disapeared.
[ Impact: kill the latency while starting to read a stat tracer file ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
The "trace" prefix in struct trace_stat_session type is annoying while
reading the trace_stat.c file. It makes the lines longer, and
is not that much useful to explain the sense of this type.
Just keep "struct stat_session" for this type.
[ Impact: make the code a bit more readable ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
The blankline between each cpu's workqueue stat is not necessary, because
the cpu number is enough to part them by eye.
Old style also caused a blankline below headline, and made code complex
by using lock, disableirq and get cpu var.
Old style:
# CPU INSERTED EXECUTED NAME
# | | | |
0 8644 8644 events/0
0 0 0 cpuset
...
0 1 1 kdmflush
1 35365 35365 events/1
...
New style:
# CPU INSERTED EXECUTED NAME
# | | | |
0 8644 8644 events/0
0 0 0 cpuset
...
0 1 1 kdmflush
1 35365 35365 events/1
...
[ Impact: provide more readable code ]
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
cpu_workqueue_stats->first_entry is useless because we can retrieve the
header of a cpu workqueue using:
if (&cpu_workqueue_stats->list == workqueue_cpu_stat(cpu)->list.next)
[ Impact: cleanup ]
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
No need to use list_for_each_entry_safe() in iteration without deleting
any node, we can use list_for_each_entry() instead.
[ Impact: cleanup ]
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
v3: zhaolei@cn.fujitsu.com: Change TRACE_EVENT definition to new format
introduced by Steven Rostedt: consolidate trace and trace_event headers
v2: kosaki@jp.fujitsu.com: print the function names instead of addr, and zap
the work addr
v1: zhaolei@cn.fujitsu.com: Make workqueue tracepoints use TRACE_EVENT macro
TRACE_EVENT is a more generic way to define tracepoints.
Doing so adds these new capabilities to the tracepoints:
- zero-copy and per-cpu splice() tracing
- binary tracing without printf overhead
- structured logging records exposed under /debug/tracing/events
- trace events embedded in function tracer output and other plugins
- user-defined, per tracepoint filter expressions
Then, this patch converts DEFINE_TRACE to TRACE_EVENT in workqueue related
tracepoints.
[ Impact: expand workqueue tracer to events tracing ]
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This patch adds __print_symbolic which is similar to __print_flags but
works for an enumeration type instead. That is, there is only a one to one
mapping between the values and the symbols. When a match is made, then
it is printed, otherwise the hex value is outputed.
[ Impact: add interface for showing symbol names in events ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Developers have been asking for the ability in the ftrace event tracer
to display names of bits in a flags variable.
Instead of printing out c2, it would be easier to read FOO|BAR|GOO,
assuming that FOO is bit 1, BAR is bit 6 and GOO is bit 7.
Some examples where this would be useful are the state flags in a context
switch, kmalloc flags, and even permision flags in accessing files.
[
v2 changes include:
Frederic Weisbecker's idea of using a mask instead of bits,
thus we can output GFP_KERNEL instead of GPF_WAIT|GFP_IO|GFP_FS.
Li Zefan's idea of allowing the caller of __print_flags to add their
own delimiter (or no delimiter) where we can get for file permissions
rwx instead of r|w|x.
]
[
v3 changes:
Christoph Hellwig's idea of using an array instead of va_args.
]
[ Impact: better displaying of flags in trace output ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Always use ftrace_event_enable_disable() to enable/disable an event
so that we can factorize out the event toggling code.
[ Impact: factorize and cleanup event tracing code ]
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <4A14FDFE.2080402@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
I found that there is nothing to protect event_hash in
ftrace_find_event(). Rcu protects the event hashlist
but not the event itself while we use it after its extraction
through ftrace_find_event().
This lack of a proper locking in this spot opens a race
window between any event dereferencing and module removal.
Eg:
--Task A--
print_trace_line(trace) {
event = find_ftrace_event(trace)
--Task B--
trace_module_remove_events(mod) {
list_trace_events_module(ev, mod) {
unregister_ftrace_event(ev->event) {
hlist_del(ev->event->node)
list_del(....)
}
}
}
|--> module removed, the event has been dropped
--Task A--
event->print(trace); // Dereferencing freed memory
If the event retrieved belongs to a module and this module
is concurrently removed, we may end up dereferencing a data
from a freed module.
RCU could solve this, but it would add latency to the kernel and
forbid tracers output callbacks to call any sleepable code.
So this fix converts 'trace_event_mutex' to a read/write semaphore,
and adds trace_event_read_lock() to protect ftrace_find_event().
[ Impact: fix possible freed memory dereference in ftrace ]
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A114806.7090302@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
register_module_notifier() returns zero in the success case.
So fix the inverted fail case check in trace events modules
handler.
[ Impact: fix spurious warning on ftrace initialization]
Reported-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
debugfs directory entries for devices are not removed on some
of the failure pathes in do_blk_trace_setup().
One way to reproduce is to start blktrace on multiple devices
with insufficient Vmalloc space: Devices will fail with
a message like this:
BLKTRACESETUP(2) /dev/sdu failed: 5/Input/output error
If so, the respective entries in debugfs
(e.g. /sys/kernel/debug/block/sdu) will remain and subsequent
attempts to start blktrace on the respective devices will not
succeed due to existing directories.
[ Impact: fix /debug/tracing file cleanup corner case ]
Signed-off-by: Stefan Raspl <stefan.raspl@linux.vnet.ibm.com>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: schwidefsky@de.ibm.com
Cc: heiko.carstens@de.ibm.com
LKML-Reference: <4A1266CC.5040801@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
return zero should be correct, so fix it.
[ Impact: eliminate incorrect syslog message ]
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: rostedt@goodmis.org
LKML-Reference: <1242545498-7285-1-git-send-email-tom.leiming@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We should leave the last slot for the ending '\0'.
[ Impact: fix possible crash when the length of an operand is 128 ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A0CDC8C.30602@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
[ Impact: fix deadlock in a rare case we fail to allocate memory ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A0CDC6F.7070200@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The stack tracer stores eight entries in the ring buffer when an event
traces the stack. The output outputs all eight entries regardless of
how many entries were recorded.
This patch breaks out of the loop when a null entry is discovered.
[ Impact: only print the stack that is recorded ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This is a bit of micro-optimizations. But since the ring buffer is used
in tracing every function call, it is an extreme hot path. Every nanosecond
counts.
This change shows over 5% improvement in the ring-buffer-benchmark.
[ Impact: more efficient code ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The ring_buffer_time_stamp that is exported adds a little more overhead
than is needed for using it internally. This patch adds an internal
timestamp function that can be inlined (a single line function)
and used internally for the ring buffer.
[ Impact: a little less overhead to the ring buffer ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Doing some small changes in the fast path of the ring buffer recording
saves over 3% in the ring-buffer-benchmark test.
[ Impact: a little faster ring buffer recording ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The event length is calculated and passed in to rb_reserve_next_event
in two different locations. Having rb_reserve_next_event do the
calculations directly makes only one location to do the change and
causes the calculation to be inlined by gcc.
Before:
text data bss dec hex filename
16538 24 12 16574 40be kernel/trace/ring_buffer.o
After:
text data bss dec hex filename
16490 24 12 16526 408e kernel/trace/ring_buffer.o
[ Impact: smaller more efficient code ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The rb_reserve_next_event is only called for the data type (type = 0).
There is no reason to pass in the type to the function.
Before:
text data bss dec hex filename
16554 24 12 16590 40ce kernel/trace/ring_buffer.o
After:
text data bss dec hex filename
16538 24 12 16574 40be kernel/trace/ring_buffer.o
[ Impact: cleaner, smaller and slightly more efficient code ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Although we check if "missed" is not zero, we divide by hit + missed,
and the addition can possible overflow and become a divide by zero.
This patch checks for this case, and will report it when it happens
then modify "hit" to make the calculation be non zero.
[ Impact: prevent possible divide by zero in ring-buffer-benchmark ]
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The use of numeric constants is discouraged. It is cleaner and more
descriptive to use macros for constant time conversions.
This patch also removes an extra new line.
[ Impact: more descriptive time conversions ]
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Other parts of the kernel may need to be able to enable or disable
specific events. Especially parts that create trace events.
[ Impact: allow enabling of trace events by those that create the event ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Commit 8f31bfe538
tracing/events: clean up for ftrace_set_clr_event()
Moved out the code for ftrace_set_clr_event into a helper funciton but
did not initialize the return value. As a result, we do not warn about
a typo in the echoing of events in set_event.
This patch restores the old warning:
# echo foobar > set_event
-bash: echo: write error: Invalid argument
[ Impact: restore warning of invalid entries to set_event ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
A smarter way to figure out the output of an enable file.
[ Impact: clean up ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A0399A5.2080603@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Add a helper function __ftrace_set_clr_event(), and replace some
ftrace_set_clr_event() calls with this helper, thus we don't need any
kstrdup() or kmalloc().
As a side effect, this patch fixes an issue in self tests code, which is
similar to the one fixed in commit d6bf81ef0f
("tracing: append ":*" to internal setting of system events")
It's a small issue and won't cause any bug in fact, but we should do things
right anyway.
[ Impact: prevent spurious event-enabling in tracing self-tests ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A03998E.3020503@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
There's a WARN_ON in the ring buffer code that makes sure preemption
is disabled. It checks "!preempt_count()". But when CONFIG_PREEMPT is not
enabled, preempt_count() is always zero, and this will trigger the warning.
[ Impact: prevent false warning on non preemptible kernels ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
It is nice to see the overhead of the benchmark test when tracing is
disabled. That is, we turn off the ring buffer just to see what the
cost of running the loop that calls into the ring buffer is.
Currently, if no entries wer made, we get 0. This is not informative.
This patch changes it to check if we had any "missed" (non recorded)
events. If so, a total count is also reported.
[ Impact: evaluate the over head of the ring buffer benchmark test ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Calling cond_resched at every iteration of the loop adds a bit of
overhead to the benchmark.
This patch does two things.
1) only calls cond-resched when CONFIG_PREEMPT is not enabled
2) only calls cond-resched after so many traces has been performed.
[ Impact: less overhead to the ring-buffer-benchmark ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Tracing can be very helpful to debug the kernel. When DEBUG_KERNEL is
enabled it is nice to enable the trace menu as well.
This patch only make the tracing menu enabled by default, it does not
make any of the tracers enabled. And the menu is only enabled by
default if DEBUG_KERNEL is enabled.
[ Impact: show tracing options to those debugging the kernel ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The system enabling of events uses the same code as the set_event file.
It passes in the name of the system to the parser and that will enable
all the events that has that system as a name.
The problem is that it will also enable events with the same name as the
system.
If you have system name foo, and system name bar, but within the system
bar, there exists an event called foo. By setting the system name foo,
you will also be enabling the event foo in the system bar. This is not
an expected result.
The solution is to pass in "foo:*", which will only enable the system
foo and not events called foo.
[ Impact: prevent accidental enabling of events with same name as a system ]
Reported-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Ingo Molnar thought that the code to calculate the time in cond_resched
is a bit too ugly and is not needed. This patch removes it and replaces
it with a simple call to cond_resched. I kept the comment that explains
the reason for the cond_resched.
[ Impact: remove ugly code ]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Merge reason: this topic is ready for upstream now. It passed
Oleg's review and Andrew had no further mm/*
objections/observations either.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Merge reason: tracing/core was on a .30-rc1 base and was missing out on
on a handful of tracing fixes present in .30-rc5-almost.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In filter_add_subsystem_pred() we should release event_mutex before
calling filter_free_subsystem_preds(), since both functions hold
event_mutex.
[ Impact: fix deadlock when writing invalid pred into subsystem filter ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: tzanussi@gmail.com
Cc: a.p.zijlstra@chello.nl
Cc: fweisbec@gmail.com
Cc: rostedt@goodmis.org
LKML-Reference: <4A028993.7020509@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When we set a filter for an event, such as:
echo "name == my_lock_name" > \
/debug/tracing/events/lockdep/lock_acquired/filter
then the following order of token type is parsed:
- space
- operator
- parentheses
- operand
Because the operators and parentheses have a higher precedence
than the operand characters, which is normal, then we can't
use any string containing such special characters:
()=<>!&|
To get this support and also avoid ambiguous intepretation from
the parser or the human, we can do it using double quotes so that
we keep the usual languages habits.
Then after this patch you can still declare string condition like
before:
echo name == myname
But if you want to compare against a string containing an operator
character, you can use double quotes:
echo 'name == "&myname"'
Don't forget to include the whole expression into single quotes or
the double ones will be eaten by echo.
[ Impact: support strings with special characters for tracing filters ]
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Zhaolei <zhaolei@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Currently the filtering infrastructure supports well the
numeric types and fixed sized array types.
But the recently added __string() field uses a specific
indirect offset mechanism which requires a specific
predicate. Until now it wasn't supported.
This patch adds this support and implies very few changes,
only a new predicate is needed, the management of this specific
field can be done through the usual string helpers in the
filtering infrastructure.
[ Impact: support all kinds of strings in the tracing filters ]
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Zhaolei <zhaolei@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
With the current event directory, you can only enable individual events.
The file debugfs/tracing/set_event is used to be able to enable or
disable several events at once. But that can still be awkward.
This patch adds hierarchical enabling of events. That is, each directory
in debugfs/tracing/events has an "enable" file. This file can enable
or disable all events within the directory and below.
# echo 1 > /debugfs/tracing/events/enable
will enable all events.
# echo 1 > /debugfs/tracing/events/sched/enable
will enable all events in the sched subsystem.
# echo 1 > /debugfs/tracing/events/enable
# echo 0 > /debugfs/tracing/events/irq/enable
will enable all events, but then disable just the irq subsystem events.
When reading one of these enable files, there are four results:
0 - all events this file affects are disabled
1 - all events this file affects are enabled
X - there is a mixture of events enabled and disabled
? - this file does not affect any event
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Li Zefan found that there's a race using the event ids of events and
modules. When a module is loaded, an event id is incremented. We only
have 16 bits for event ids (65536) and there is a possible (but highly
unlikely) race that we could load and unload a module that registers
events so many times that the event id counter overflows.
When it overflows, it then restarts and goes looking for available
ids. An id is available if it was added by a module and released.
The race is if you have one module add an id, and then is removed.
Another module loaded can use that same event id. But if the old module
still had events in the ring buffer, the new module's call back would
get bogus data. At best (and most likely) the output would just be
garbage. But if the module for some reason used pointers (not recommended)
then this could potentially crash.
The safest thing to do is just reset the ring buffer if a module that
registered events is removed.
[ Impact: prevent unpredictable results of event id overflows ]
Reported-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <49FEAFD0.30106@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The ring buffer benchmark/test runs a producer for 10 seconds.
This is done with preemption and interrupts enabled. But if the kernel
is not compiled with CONFIG_PREEMPT, it basically stops everything
but interrupts for 10 seconds.
Although this is just a test and is not for production, this attribute
can be quite annoying. It can also spawn badness elsewhere.
This patch solves the issues by calling "cond_resched" when the system
is not compiled with CONFIG_PREEMPT. It also keeps track of the time
spent to call cond_resched such that it does not go against the
time calculations. That is, if the task schedules away, the time scheduled
out is removed from the test data. Note, this only works for non PREEMPT
because we do not know when the task is scheduled out if we have PREEMPT
enabled.
[ Impact: prevent test from stopping the world for 10 seconds ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Ingo Molnar thought the code would be cleaner if we used a function call
instead of a goto for moving the tail page. After implementing this,
it seems that gcc still inlines the result and the output is pretty much
the same. Since this is considered a cleaner approach, might as well
implement it.
[ Impact: code clean up ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The result of the allocation of the ring buffer read page in the
ring buffer bench mark does not check the return to see if a page
was actually allocated. This patch fixes that.
[ Impact: avoid NULL dereference ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
