On 2/6/2024 4:46 AM, Huang Yiwei wrote: > 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 > or multiple trace instances: > > - 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> > - ftrace_dump_on_oops[=2/orig_cpu],<instance1_name>[=2/orig_cpu], > <instrance2_name>[=2/orig_cpu]: new behavior -- dump the global trace > buffer and multiple instance buffer on all CPUs, or only dump on CPU > that triggered the oops if =2 or =orig_cpu is given > > 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/20240119080824.907101-1-quic_hyiwei@xxxxxxxxxxx/ > > .../admin-guide/kernel-parameters.txt | 26 ++- > Documentation/admin-guide/sysctl/kernel.rst | 30 +++- > include/linux/ftrace.h | 4 +- > include/linux/kernel.h | 1 + > kernel/sysctl.c | 4 +- > kernel/trace/trace.c | 156 +++++++++++++----- > kernel/trace/trace_selftest.c | 2 +- > 7 files changed, 168 insertions(+), 55 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 31b3a25680d0..f4c05a43b561 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -1561,12 +1561,28 @@ > 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_opps[=2(orig_cpu) | =<instance>][,<instance> | You introduced a typo to 'oops' here. > + ,<instance>=2(orig_cpu)] > [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 > - dump only the buffer of the CPU that triggered the > - oops. > + If no parameter is passed, ftrace will dump global > + buffers of all CPUs, if you pass 2 or orig_cpu, it> + will dump only the buffer of the CPU that triggered > + the oops, or the specific instance will be dumped if > + its name is passed. Multiple instance dump is also > + supported, and instances are separated by commas. Each > + instance supports only dump on CPU that triggered the > + oops by passing 2 or orig_cpu to it. > + > + ftrace_dump_on_opps=foo=orig_cpu > + > + The above will dump only the buffer of "foo" instance > + on CPU that triggered the oops. > + > + ftrace_dump_on_opps,foo,bar=orig_cpu > + > + The above will dump global buffer on all CPUs, the > + buffer of "foo" instance on all CPUs and the buffer > + of "bar" instance on CPU that triggered the oops. > > 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..ea8e5f152edc 100644 > --- a/Documentation/admin-guide/sysctl/kernel.rst > +++ b/Documentation/admin-guide/sysctl/kernel.rst > @@ -296,12 +296,30 @@ 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 on all CPUs. > +<instance>=2(orig_cpu) Dump the specific instance buffer on the CPU > + that triggered the oops. > +======================= =========================================== > + > +Multiple instance dump is also supported, and instances are separated > +by commas. If global buffer also needs to be dumped, please specify > +the dump mode (1/2/orig_cpu) first for global buffer. > + > +So for example to dump "foo" and "bar" instance buffer on all CPUs, > +user can:: > + > + echo "foo,bar" > /proc/sys/kernel/ftrace_dump_on_oops > + > +To dump global buffer and "foo" instance buffer on all > +CPUs along with the "bar" instance buffer on CPU that triggered the > +oops, user can:: > + > + echo "1,foo,bar=2" > /proc/sys/kernel/ftrace_dump_on_oops > > ftrace_enabled, stack_tracer_enabled > ==================================== > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index e8921871ef9a..54d53f345d14 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 int ftrace_dump_on_oops_enabled(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..b142a4f41d34 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_PARAM, > }; > > #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 2a7c6fd934e9..5622614d3035 100644 > --- a/kernel/trace/trace.c > +++ b/kernel/trace/trace.c > @@ -130,9 +130,12 @@ 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 > + * Multiple instance dump is also supported, and instances are seperated > + * by commas. > */ > - > -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 +181,6 @@ 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 +203,33 @@ static int __init set_cmdline_ftrace(char *str) > } > __setup("ftrace=", set_cmdline_ftrace); > > +int ftrace_dump_on_oops_enabled(void) > +{ > + if (!strcmp("0", ftrace_dump_on_oops)) > + return 0; > + else > + return 1; > +} > + > 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, "1", MAX_TRACER_SIZE); > + strscpy(ftrace_dump_on_oops + 1, str, MAX_TRACER_SIZE - 1); > + 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); > > @@ -10243,14 +10259,14 @@ 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) > + if (!ftrace_dump_on_oops_enabled()) > 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_PARAM); > > return NOTIFY_DONE; > } > @@ -10291,12 +10307,12 @@ 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); > @@ -10316,22 +10332,19 @@ void trace_init_global_iter(struct trace_iterator *iter) > iter->fmt_size = STATIC_FMT_BUF_SIZE; > } > > -void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) > +void trace_init_global_iter(struct trace_iterator *iter) > +{ > + trace_init_iter(iter, &global_trace); > +} > + > +void ftrace_dump_one(struct trace_array *tr, enum ftrace_dump_mode dump_mode) > { > /* use static because iter can be a bit big for the stack */ > static struct trace_iterator iter; > - static atomic_t dump_running; > - struct trace_array *tr = &global_trace; > unsigned int old_userobj; > unsigned long flags;> int cnt = 0, cpu; > > - /* Only allow one dump user at a time. */ > - if (atomic_inc_return(&dump_running) != 1) { > - atomic_dec(&dump_running); > - return; > - } > - > /* > * Always turn off tracing when we dump. > * We don't need to show trace output of what happens > @@ -10340,12 +10353,12 @@ 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); > @@ -10356,21 +10369,15 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) > /* don't look at user memory in panic mode */ > tr->trace_flags &= ~TRACE_ITER_SYM_USEROBJ; > > - switch (oops_dump_mode) { > - case DUMP_ALL: > - iter.cpu_file = RING_BUFFER_ALL_CPUS; > - break; > - case DUMP_ORIG: > + if (dump_mode == DUMP_ORIG) > iter.cpu_file = raw_smp_processor_id(); > - break; > - case DUMP_NONE: > - goto out_enable; > - default: > - printk(KERN_TRACE "Bad dumping mode, switching to all CPUs dump\n"); > + else > iter.cpu_file = RING_BUFFER_ALL_CPUS; > - } > > - printk(KERN_TRACE "Dumping ftrace buffer:\n"); > + if (tr == &global_trace) > + printk(KERN_TRACE "Dumping ftrace buffer:\n"); > + else > + printk(KERN_TRACE "Dumping ftrace instance %s buffer:\n", tr->name); > > /* Did function tracer already get disabled? */ > if (ftrace_is_dead()) { > @@ -10412,15 +10419,84 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) > else > printk(KERN_TRACE "---------------------------------\n"); > > - out_enable: > tr->trace_flags |= old_userobj; > > for_each_tracing_cpu(cpu) { > atomic_dec(&per_cpu_ptr(iter.array_buffer->data, cpu)->disabled); > } > - atomic_dec(&dump_running); > local_irq_restore(flags); > } > + > +static void ftrace_dump_by_param(void) > +{ > + bool first_param = true; > + char dump_param[MAX_TRACER_SIZE]; > + char *buf, *token, *inst_name; > + struct trace_array *tr; > + > + strscpy(dump_param, ftrace_dump_on_oops, MAX_TRACER_SIZE); > + buf = dump_param; > + > + while ((token = strsep(&buf, ",")) != NULL) { > + if (first_param) { > + first_param = false; > + if (!strcmp("0", token)) > + continue; > + else if (!strcmp("1", token)) { > + ftrace_dump_one(&global_trace, DUMP_ALL); > + continue; > + } > + else if (!strcmp("2", token) || > + !strcmp("orig_cpu", token)) { > + ftrace_dump_one(&global_trace, DUMP_ORIG); DUMP_PARAM and ftrace_dump_by_param() is a bit of a misnomer, because it optionally also dumps the original buffer, not just the instances. That's probably OK though. FWIW: Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> Btw, hopefully the "trace off on warning" and related boot parameters also apply to instances, I haven't personally checked but I often couple those with the dump-on-oops ones. Thanks.
