kernel_optimize_test/kernel/trace
Steven Rostedt 7614c3dc74 ftrace: Use schedule_on_each_cpu() as a heavy synchronize_sched()
The function tracer uses preempt_disable/enable_notrace() for
synchronization between reading registered ftrace_ops and unregistering
them.

Most of the ftrace_ops are global permanent structures that do not
require this synchronization. That is, ops may be added and removed from
the hlist but are never freed, and wont hurt if a synchronization is
missed.

But this is not true for dynamically created ftrace_ops or control_ops,
which are used by the perf function tracing.

The problem here is that the function tracer can be used to trace
kernel/user context switches as well as going to and from idle.
Basically, it can be used to trace blind spots of the RCU subsystem.
This means that even though preempt_disable() is done, a
synchronize_sched() will ignore CPUs that haven't made it out of user
space or idle. These can include functions that are being traced just
before entering or exiting the kernel sections.

To implement the RCU synchronization, instead of using
synchronize_sched() the use of schedule_on_each_cpu() is performed. This
means that when a dynamically allocated ftrace_ops, or a control ops is
being unregistered, all CPUs must be touched and execute a ftrace_sync()
stub function via the work queues. This will rip CPUs out from idle or
in dynamic tick mode. This only happens when a user disables perf
function tracing or other dynamically allocated function tracers, but it
allows us to continue to debug RCU and context tracking with function
tracing.

Link: http://lkml.kernel.org/r/1369785676.15552.55.camel@gandalf.local.home

Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2013-06-11 18:38:50 -04:00
..
blktrace.c Merge branch 'for-3.10/drivers' of git://git.kernel.dk/linux-block 2013-05-08 11:51:05 -07:00
ftrace.c ftrace: Use schedule_on_each_cpu() as a heavy synchronize_sched() 2013-06-11 18:38:50 -04:00
Kconfig ring-buffer: Select IRQ_WORK 2013-05-03 19:24:17 -04:00
Makefile trace: Stop compiling in trace_clock unconditionally 2012-09-13 22:52:08 -04:00
power-traces.c PM / tracing: remove deprecated power trace API 2013-01-26 00:39:12 +01:00
ring_buffer_benchmark.c tracing: Use NUMA allocation for per-cpu ring buffer pages 2011-06-14 22:04:39 -04:00
ring_buffer.c ring-buffer: Do not poll non allocated cpu buffers 2013-05-28 10:53:20 -04:00
rpm-traces.c PM / Runtime: Introduce trace points for tracing rpm_* functions 2011-09-27 22:53:27 +02:00
trace_branch.c tracing: Fix the branch tracer that broke with buffer change 2013-03-15 00:35:54 -04:00
trace_clock.c tracing: Add "uptime" trace clock that uses jiffies 2013-03-15 00:36:09 -04:00
trace_entries.h tracing: Add trace_puts() for even faster trace_printk() tracing 2013-03-15 00:35:55 -04:00
trace_event_perf.c perf/core improvements and fixes: 2012-08-21 11:27:00 +02:00
trace_events_filter_test.h tracing/filter: Add startup tests for events filter 2011-08-19 14:35:59 -04:00
trace_events_filter.c tracing: Fix leaks of filter preds 2013-05-15 13:49:18 -04:00
trace_events.c tracing/trivial: Consolidate error return condition 2013-06-11 18:38:49 -04:00
trace_export.c tracing: Fix some section mismatch warnings 2013-03-15 00:34:54 -04:00
trace_functions_graph.c tracing: Consolidate max_tr into main trace_array structure 2013-03-15 00:35:40 -04:00
trace_functions.c tracing: Add function probe to trigger a ftrace dump of current CPU trace 2013-06-11 18:38:48 -04:00
trace_irqsoff.c tracing: Add function-trace option to disable function tracing of latency tracers 2013-03-15 00:36:08 -04:00
trace_kdb.c tracing: Consolidate max_tr into main trace_array structure 2013-03-15 00:35:40 -04:00
trace_kprobe.c tracing/kprobes: Make print_*probe_event static 2013-05-15 13:50:24 -04:00
trace_mmiotrace.c tracing: Consolidate max_tr into main trace_array structure 2013-03-15 00:35:40 -04:00
trace_nop.c
trace_output.c Tracing updates for Linux 3.10 2013-04-29 13:55:38 -07:00
trace_output.h tracing: Rename trace_event_mutex to trace_event_sem 2013-03-15 13:22:10 -04:00
trace_printk.c tracing: Add percpu buffers for trace_printk() 2012-04-23 21:15:55 -04:00
trace_probe.c tracing: Replace strict_strto* with kstrto* 2012-10-31 16:45:23 -04:00
trace_probe.h uprobes/tracing: Introduce is_trace_uprobe_enabled() 2013-02-08 18:24:30 +01:00
trace_sched_switch.c tracing: Consolidate max_tr into main trace_array structure 2013-03-15 00:35:40 -04:00
trace_sched_wakeup.c tracing: Add function-trace option to disable function tracing of latency tracers 2013-03-15 00:36:08 -04:00
trace_selftest_dynamic.c ftrace: Add self-tests for multiple function trace users 2011-05-18 19:24:51 -04:00
trace_selftest.c tracing: Fix bad parameter passed in branch selftest 2013-05-29 16:00:03 -04:00
trace_stack.c Tracing updates for Linux 3.10 2013-04-29 13:55:38 -07:00
trace_stat.c tracing: Check return value of tracing_init_dentry() 2013-04-12 23:02:32 -04:00
trace_stat.h tracing/stat: Add stat_release() callback 2009-07-10 12:14:05 +02:00
trace_syscalls.c tracing: Fix comment about prefix in arch_syscall_match_sym_name() 2013-03-15 13:22:09 -04:00
trace_uprobe.c uprobes/perf: Avoid perf_trace_buf_prepare/submit if ->perf_events is empty 2013-04-15 17:39:52 +02:00
trace.c tracing: Fix file mode of free_buffer 2013-06-11 18:38:49 -04:00
trace.h Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-04-30 07:41:01 -07:00