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tracing: Prevent buffer overwrite disabled for latency tracers

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The latency tracers require the buffers to be in overwrite mode,
otherwise they get screwed up. Force the buffers to stay in overwrite
mode when latency tracers are enabled.

Added a flag_changed() method to the tracer structure to allow
the tracers to see what flags are being changed, and also be able
to prevent the change from happing.

Cc: stable@vger.kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Red Hat) 2013-03-14 15:03:53 -04:00 • committed by Steven Rostedt
parent 8090282265
commit 613f04a0f5
4 changed files with 65 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

19
kernel/trace/trace_irqsoff.c
View file

@ -32,7 +32,7 @@ enum {
static int trace_type __read_mostly;
static int save_lat_flag;
static int save_flags;
static void stop_irqsoff_tracer(struct trace_array *tr, int graph);
static int start_irqsoff_tracer(struct trace_array *tr, int graph);
@ -558,8 +558,11 @@ static void stop_irqsoff_tracer(struct trace_array *tr, int graph)
static void __irqsoff_tracer_init(struct trace_array *tr)
{
save_lat_flag = trace_flags & TRACE_ITER_LATENCY_FMT;
trace_flags |= TRACE_ITER_LATENCY_FMT;
save_flags = trace_flags;
/* non overwrite screws up the latency tracers */
set_tracer_flag(TRACE_ITER_OVERWRITE, 1);
set_tracer_flag(TRACE_ITER_LATENCY_FMT, 1);
tracing_max_latency = 0;
irqsoff_trace = tr;
@ -573,10 +576,13 @@ static void __irqsoff_tracer_init(struct trace_array *tr)
static void irqsoff_tracer_reset(struct trace_array *tr)
{
int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
stop_irqsoff_tracer(tr, is_graph());
if (!save_lat_flag)
trace_flags &= ~TRACE_ITER_LATENCY_FMT;
set_tracer_flag(TRACE_ITER_LATENCY_FMT, lat_flag);
set_tracer_flag(TRACE_ITER_OVERWRITE, overwrite_flag);
}
static void irqsoff_tracer_start(struct trace_array *tr)
@ -609,6 +615,7 @@ static struct tracer irqsoff_tracer __read_mostly =
.print_line = irqsoff_print_line,
.flags = &tracer_flags,
.set_flag = irqsoff_set_flag,
.flag_changed = trace_keep_overwrite,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_irqsoff,
#endif
@ -642,6 +649,7 @@ static struct tracer preemptoff_tracer __read_mostly =
.print_line = irqsoff_print_line,
.flags = &tracer_flags,
.set_flag = irqsoff_set_flag,
.flag_changed = trace_keep_overwrite,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_preemptoff,
#endif
@ -677,6 +685,7 @@ static struct tracer preemptirqsoff_tracer __read_mostly =
.print_line = irqsoff_print_line,
.flags = &tracer_flags,
.set_flag = irqsoff_set_flag,
.flag_changed = trace_keep_overwrite,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_preemptirqsoff,
#endif