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Date: Thu, 14 Mar 2013 17:33:06 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org
Cc: Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Frederic Weisbecker <fweisbec@...il.com>,
<stable@...r.kernel.org>
Subject: [PATCH 3/3] tracing: Prevent buffer overwrite disabled for latency tracers
From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
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@...r.kernel.org
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
kernel/trace/trace.c | 38 +++++++++++++++++++++++++++++++------
kernel/trace/trace.h | 6 ++++++
kernel/trace/trace_irqsoff.c | 19 ++++++++++++++-----
kernel/trace/trace_sched_wakeup.c | 18 +++++++++++++-----
4 files changed, 65 insertions(+), 16 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index eaaccd8..1354f5d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2881,11 +2881,25 @@ static int set_tracer_option(struct tracer *trace, char *cmp, int neg)
return -EINVAL;
}
-static void set_tracer_flags(unsigned int mask, int enabled)
+/* Some tracers require overwrite to stay enabled */
+int trace_keep_overwrite(struct tracer *tracer, u32 mask, int set)
+{
+ if (tracer->enabled && (mask & TRACE_ITER_OVERWRITE) && !set)
+ return -1;
+
+ return 0;
+}
+
+int set_tracer_flag(unsigned int mask, int enabled)
{
/* do nothing if flag is already set */
if (!!(trace_flags & mask) == !!enabled)
- return;
+ return 0;
+
+ /* Give the tracer a chance to approve the change */
+ if (current_trace->flag_changed)
+ if (current_trace->flag_changed(current_trace, mask, !!enabled))
+ return -EINVAL;
if (enabled)
trace_flags |= mask;
@@ -2902,13 +2916,15 @@ static void set_tracer_flags(unsigned int mask, int enabled)
if (mask == TRACE_ITER_PRINTK)
trace_printk_start_stop_comm(enabled);
+
+ return 0;
}
static int trace_set_options(char *option)
{
char *cmp;
int neg = 0;
- int ret = 0;
+ int ret = -ENODEV;
int i;
cmp = strstrip(option);
@@ -2922,7 +2938,7 @@ static int trace_set_options(char *option)
for (i = 0; trace_options[i]; i++) {
if (strcmp(cmp, trace_options[i]) == 0) {
- set_tracer_flags(1 << i, !neg);
+ ret = set_tracer_flag(1 << i, !neg);
break;
}
}
@@ -2941,6 +2957,7 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
{
char buf[64];
+ int ret;
if (cnt >= sizeof(buf))
return -EINVAL;
@@ -2950,7 +2967,9 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
buf[cnt] = 0;
- trace_set_options(buf);
+ ret = trace_set_options(buf);
+ if (ret < 0)
+ return ret;
*ppos += cnt;
@@ -3254,6 +3273,9 @@ static int tracing_set_tracer(const char *buf)
goto out;
trace_branch_disable();
+
+ current_trace->enabled = false;
+
if (current_trace->reset)
current_trace->reset(tr);
@@ -3298,6 +3320,7 @@ static int tracing_set_tracer(const char *buf)
}
current_trace = t;
+ current_trace->enabled = true;
trace_branch_enable(tr);
out:
mutex_unlock(&trace_types_lock);
@@ -4786,9 +4809,12 @@ trace_options_core_write(struct file *filp, const char __user *ubuf, size_t cnt,
return -EINVAL;
mutex_lock(&trace_types_lock);
- set_tracer_flags(1 << index, val);
+ ret = set_tracer_flag(1 << index, val);
mutex_unlock(&trace_types_lock);
+ if (ret < 0)
+ return ret;
+
*ppos += cnt;
return cnt;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 57d7e53..2081971 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -283,11 +283,15 @@ struct tracer {
enum print_line_t (*print_line)(struct trace_iterator *iter);
/* If you handled the flag setting, return 0 */
int (*set_flag)(u32 old_flags, u32 bit, int set);
+ /* Return 0 if OK with change, else return non-zero */
+ int (*flag_changed)(struct tracer *tracer,
+ u32 mask, int set);
struct tracer *next;
struct tracer_flags *flags;
bool print_max;
bool use_max_tr;
bool allocated_snapshot;
+ bool enabled;
};
@@ -943,6 +947,8 @@ extern const char *__stop___trace_bprintk_fmt[];
void trace_printk_init_buffers(void);
void trace_printk_start_comm(void);
+int trace_keep_overwrite(struct tracer *tracer, u32 mask, int set);
+int set_tracer_flag(unsigned int mask, int enabled);
#undef FTRACE_ENTRY
#define FTRACE_ENTRY(call, struct_name, id, tstruct, print, filter) \
diff --git a/kernel/trace/trace_irqsoff.c b/kernel/trace/trace_irqsoff.c
index 713a2ca..443b25b 100644
--- a/kernel/trace/trace_irqsoff.c
+++ b/kernel/trace/trace_irqsoff.c
@@ -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
diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 75aa97f..fde652c 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -36,7 +36,7 @@ static void __wakeup_reset(struct trace_array *tr);
static int wakeup_graph_entry(struct ftrace_graph_ent *trace);
static void wakeup_graph_return(struct ftrace_graph_ret *trace);
-static int save_lat_flag;
+static int save_flags;
#define TRACE_DISPLAY_GRAPH 1
@@ -540,8 +540,11 @@ static void stop_wakeup_tracer(struct trace_array *tr)
static int __wakeup_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;
wakeup_trace = tr;
@@ -563,12 +566,15 @@ static int wakeup_rt_tracer_init(struct trace_array *tr)
static void wakeup_tracer_reset(struct trace_array *tr)
{
+ int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
+ int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
+
stop_wakeup_tracer(tr);
/* make sure we put back any tasks we are tracing */
wakeup_reset(tr);
- 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 wakeup_tracer_start(struct trace_array *tr)
@@ -594,6 +600,7 @@ static struct tracer wakeup_tracer __read_mostly =
.print_line = wakeup_print_line,
.flags = &tracer_flags,
.set_flag = wakeup_set_flag,
+ .flag_changed = trace_keep_overwrite,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
@@ -615,6 +622,7 @@ static struct tracer wakeup_rt_tracer __read_mostly =
.print_line = wakeup_print_line,
.flags = &tracer_flags,
.set_flag = wakeup_set_flag,
+ .flag_changed = trace_keep_overwrite,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_wakeup,
#endif
--
1.7.10.4
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