[PATCH v3] tracing: Support to dump instance traces by ftrace_dump_on_oops
From: Huang Yiwei
Date: Fri Jan 19 2024 - 03:09:26 EST
Currently ftrace only dumps the global trace buffer on an OOPs. For
debugging a production usecase, instance trace will be helpful to
check specific problems since global trace buffer may be used for
other purposes.
This patch extend the ftrace_dump_on_oops parameter to dump a specific
trace instance:
- ftrace_dump_on_oops=0: as before -- don't dump
- ftrace_dump_on_oops[=1]: as before -- dump the global trace buffer
on all CPUs
- ftrace_dump_on_oops=2 or =orig_cpu: as before -- dump the global
trace buffer on CPU that triggered the oops
- ftrace_dump_on_oops=<instance_name>: new behavior -- dump the
tracing instance matching <instance_name>
Also, the sysctl node can handle the input accordingly.
Cc: Ross Zwisler <zwisler@xxxxxxxxxx>
Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Signed-off-by: Huang Yiwei <quic_hyiwei@xxxxxxxxxxx>
---
Link: https://lore.kernel.org/linux-trace-kernel/20221209125310.450aee97@xxxxxxxxxxxxxxxxxx/
.../admin-guide/kernel-parameters.txt | 9 +--
Documentation/admin-guide/sysctl/kernel.rst | 11 ++--
include/linux/ftrace.h | 4 +-
include/linux/kernel.h | 1 +
kernel/sysctl.c | 4 +-
kernel/trace/trace.c | 64 ++++++++++++++-----
kernel/trace/trace_selftest.c | 2 +-
7 files changed, 65 insertions(+), 30 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index a36cf8cc582c..b3aa533253f1 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1559,12 +1559,13 @@
The above will cause the "foo" tracing instance to trigger
a snapshot at the end of boot up.
- ftrace_dump_on_oops[=orig_cpu]
+ ftrace_dump_on_oops[=orig_cpu | =<instance>]
[FTRACE] will dump the trace buffers on oops.
- If no parameter is passed, ftrace will dump
- buffers of all CPUs, but if you pass orig_cpu, it will
+ If no parameter is passed, ftrace will dump global
+ buffers of all CPUs, if you pass orig_cpu, it will
dump only the buffer of the CPU that triggered the
- oops.
+ oops, or specific instance will be dumped if instance
+ name is passed.
ftrace_filter=[function-list]
[FTRACE] Limit the functions traced by the function
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 6584a1f9bfe3..ecf036b63c48 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -296,11 +296,12 @@ kernel panic). This will output the contents of the ftrace buffers to
the console. This is very useful for capturing traces that lead to
crashes and outputting them to a serial console.
-= ===================================================
-0 Disabled (default).
-1 Dump buffers of all CPUs.
-2 Dump the buffer of the CPU that triggered the oops.
-= ===================================================
+=========== ===================================================
+0 Disabled (default).
+1 Dump buffers of all CPUs.
+2(orig_cpu) Dump the buffer of the CPU that triggered the oops.
+<instance> Dump the specific instance buffer.
+=========== ===================================================
ftrace_enabled, stack_tracer_enabled
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index e8921871ef9a..f20de4621ec1 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -1151,7 +1151,9 @@ static inline void unpause_graph_tracing(void) { }
#ifdef CONFIG_TRACING
enum ftrace_dump_mode;
-extern enum ftrace_dump_mode ftrace_dump_on_oops;
+#define MAX_TRACER_SIZE 100
+extern char ftrace_dump_on_oops[];
+extern enum ftrace_dump_mode get_ftrace_dump_mode(void);
extern int tracepoint_printk;
extern void disable_trace_on_warning(void);
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d9ad21058eed..de4a76036372 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -255,6 +255,7 @@ enum ftrace_dump_mode {
DUMP_NONE,
DUMP_ALL,
DUMP_ORIG,
+ DUMP_INSTANCE,
};
#ifdef CONFIG_TRACING
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 157f7ce2942d..81cc974913bb 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1710,9 +1710,9 @@ static struct ctl_table kern_table[] = {
{
.procname = "ftrace_dump_on_oops",
.data = &ftrace_dump_on_oops,
- .maxlen = sizeof(int),
+ .maxlen = MAX_TRACER_SIZE,
.mode = 0644,
- .proc_handler = proc_dointvec,
+ .proc_handler = proc_dostring,
},
{
.procname = "traceoff_on_warning",
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a0defe156b57..9a76a278e5c3 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -130,9 +130,10 @@ cpumask_var_t __read_mostly tracing_buffer_mask;
* /proc/sys/kernel/ftrace_dump_on_oops
* Set 1 if you want to dump buffers of all CPUs
* Set 2 if you want to dump the buffer of the CPU that triggered oops
+ * Set instance name if you want to dump the specific trace instance
*/
-
-enum ftrace_dump_mode ftrace_dump_on_oops;
+/* Set to string format zero to disable by default */
+char ftrace_dump_on_oops[MAX_TRACER_SIZE] = "0";
/* When set, tracing will stop when a WARN*() is hit */
int __disable_trace_on_warning;
@@ -178,7 +179,6 @@ static void ftrace_trace_userstack(struct trace_array *tr,
struct trace_buffer *buffer,
unsigned int trace_ctx);
-#define MAX_TRACER_SIZE 100
static char bootup_tracer_buf[MAX_TRACER_SIZE] __initdata;
static char *default_bootup_tracer;
@@ -201,19 +201,32 @@ static int __init set_cmdline_ftrace(char *str)
}
__setup("ftrace=", set_cmdline_ftrace);
+enum ftrace_dump_mode get_ftrace_dump_mode(void)
+{
+ if (!strcmp("0", ftrace_dump_on_oops))
+ return DUMP_NONE;
+ else if (!strcmp("1", ftrace_dump_on_oops))
+ return DUMP_ALL;
+ else if (!strcmp("orig_cpu", ftrace_dump_on_oops) ||
+ !strcmp("2", ftrace_dump_on_oops))
+ return DUMP_ORIG;
+ else
+ return DUMP_INSTANCE;
+}
+
static int __init set_ftrace_dump_on_oops(char *str)
{
- if (*str++ != '=' || !*str || !strcmp("1", str)) {
- ftrace_dump_on_oops = DUMP_ALL;
+ if (!*str) {
+ strscpy(ftrace_dump_on_oops, "1", MAX_TRACER_SIZE);
return 1;
}
- if (!strcmp("orig_cpu", str) || !strcmp("2", str)) {
- ftrace_dump_on_oops = DUMP_ORIG;
- return 1;
- }
+ if (*str++ == '=') {
+ strscpy(ftrace_dump_on_oops, str, MAX_TRACER_SIZE);
+ return 1;
+ }
- return 0;
+ return 0;
}
__setup("ftrace_dump_on_oops", set_ftrace_dump_on_oops);
@@ -10085,14 +10098,16 @@ static struct notifier_block trace_die_notifier = {
static int trace_die_panic_handler(struct notifier_block *self,
unsigned long ev, void *unused)
{
- if (!ftrace_dump_on_oops)
+ enum ftrace_dump_mode dump_mode = get_ftrace_dump_mode();
+
+ if (!dump_mode)
return NOTIFY_DONE;
/* The die notifier requires DIE_OOPS to trigger */
if (self == &trace_die_notifier && ev != DIE_OOPS)
return NOTIFY_DONE;
- ftrace_dump(ftrace_dump_on_oops);
+ ftrace_dump(dump_mode);
return NOTIFY_DONE;
}
@@ -10133,12 +10148,12 @@ trace_printk_seq(struct trace_seq *s)
trace_seq_init(s);
}
-void trace_init_global_iter(struct trace_iterator *iter)
+static void trace_init_iter(struct trace_iterator *iter, struct trace_array *tr)
{
- iter->tr = &global_trace;
+ iter->tr = tr;
iter->trace = iter->tr->current_trace;
iter->cpu_file = RING_BUFFER_ALL_CPUS;
- iter->array_buffer = &global_trace.array_buffer;
+ iter->array_buffer = &tr->array_buffer;
if (iter->trace && iter->trace->open)
iter->trace->open(iter);
@@ -10158,6 +10173,11 @@ void trace_init_global_iter(struct trace_iterator *iter)
iter->fmt_size = STATIC_FMT_BUF_SIZE;
}
+void trace_init_global_iter(struct trace_iterator *iter)
+{
+ trace_init_iter(iter, &global_trace);
+}
+
void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
{
/* use static because iter can be a bit big for the stack */
@@ -10168,6 +10188,15 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
unsigned long flags;
int cnt = 0, cpu;
+ if (oops_dump_mode == DUMP_INSTANCE) {
+ tr = trace_array_find(ftrace_dump_on_oops);
+ if (!tr) {
+ printk(KERN_TRACE "Instance %s not found\n",
+ ftrace_dump_on_oops);
+ return;
+ }
+ }
+
/* Only allow one dump user at a time. */
if (atomic_inc_return(&dump_running) != 1) {
atomic_dec(&dump_running);
@@ -10182,12 +10211,12 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
* If the user does a sysrq-z, then they can re-enable
* tracing with echo 1 > tracing_on.
*/
- tracing_off();
+ tracer_tracing_off(tr);
local_irq_save(flags);
/* Simulate the iterator */
- trace_init_global_iter(&iter);
+ trace_init_iter(&iter, tr);
for_each_tracing_cpu(cpu) {
atomic_inc(&per_cpu_ptr(iter.array_buffer->data, cpu)->disabled);
@@ -10200,6 +10229,7 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
switch (oops_dump_mode) {
case DUMP_ALL:
+ case DUMP_INSTANCE:
iter.cpu_file = RING_BUFFER_ALL_CPUS;
break;
case DUMP_ORIG:
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index 529590499b1f..a9750a680324 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -768,7 +768,7 @@ static int trace_graph_entry_watchdog(struct ftrace_graph_ent *trace)
if (unlikely(++graph_hang_thresh > GRAPH_MAX_FUNC_TEST)) {
ftrace_graph_stop();
printk(KERN_WARNING "BUG: Function graph tracer hang!\n");
- if (ftrace_dump_on_oops) {
+ if (get_ftrace_dump_mode()) {
ftrace_dump(DUMP_ALL);
/* ftrace_dump() disables tracing */
tracing_on();
--
2.25.1