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Date: Thu, 2 Apr 2009 14:17:55 +0200
From: Frederic Weisbecker <fweisbec@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
Tom Zanussi <tzanussi@...il.com>,
Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 1/4] tracing/filters: add run-time field descriptions
to TRACE_EVENT_FORMAT events
On Thu, Apr 02, 2009 at 01:27:22AM -0400, Steven Rostedt wrote:
> From: Tom Zanussi <tzanussi@...il.com>
>
> This patch adds run-time field descriptions to all the event formats
> exported using TRACE_EVENT_FORMAT. It also hooks up all the tracers
> that use them (i.e. the tracers in the 'ftrace subsystem') so they can
> also have their output filtered by the event-filtering mechanism.
>
> When I was testing this, there were a couple of things that fooled me
> into thinking the filters weren't working, when actually they were -
> I'll mention them here so others don't make the same mistakes (and file
> bug reports. ;-)
>
> One is that some of the tracers trace multiple events e.g. the
> sched_switch tracer uses the context_switch and wakeup events, and if
> you don't set filters on all of the traced events, the unfiltered output
> from the events without filters on them can make it look like the
> filtering as a whole isn't working properly, when actually it is doing
> what it was asked to do - it just wasn't asked to do the right thing.
>
> The other is that for the really high-volume tracers e.g. the function
> tracer, the volume of filtered events can be so high that it pushes the
> unfiltered events out of the ring buffer before they can be read so e.g.
> cat'ing the trace file repeatedly shows either no output, or once in
> awhile some output but that isn't there the next time you read the
> trace, which isn't what you normally expect when reading the trace file.
> If you read from the trace_pipe file though, you can catch them before
> they disappear.
>
> Changes from v1:
>
> As suggested by Frederic Weisbecker:
>
> - get rid of externs in functions
> - added unlikely() to filter_check_discard()
Thanks Tom!
> Signed-off-by: Tom Zanussi <tzanussi@...il.com>
> Signed-off-by: Steven Rostedt <srostedt@...hat.com>
> ---
> kernel/trace/kmemtrace.c | 6 ++++
> kernel/trace/trace.c | 25 +++++++++++++++
> kernel/trace/trace.h | 20 ++++++++++++
> kernel/trace/trace_branch.c | 3 ++
> kernel/trace/trace_event_types.h | 6 ++-
> kernel/trace/trace_events.c | 7 ++++
> kernel/trace/trace_events_filter.c | 4 +-
> kernel/trace/trace_events_stage_2.h | 7 ----
> kernel/trace/trace_export.c | 57 +++++++++++++++++++++++++++++++++--
> kernel/trace/trace_hw_branches.c | 2 +
> kernel/trace/trace_power.c | 4 ++
> 11 files changed, 127 insertions(+), 14 deletions(-)
>
> diff --git a/kernel/trace/kmemtrace.c b/kernel/trace/kmemtrace.c
> index 5011f4d..65aba48 100644
> --- a/kernel/trace/kmemtrace.c
> +++ b/kernel/trace/kmemtrace.c
> @@ -42,6 +42,7 @@ static inline void kmemtrace_alloc(enum kmemtrace_type_id type_id,
> gfp_t gfp_flags,
> int node)
> {
> + struct ftrace_event_call *call = &event_kmem_alloc;
> struct trace_array *tr = kmemtrace_array;
> struct kmemtrace_alloc_entry *entry;
> struct ring_buffer_event *event;
> @@ -62,6 +63,8 @@ static inline void kmemtrace_alloc(enum kmemtrace_type_id type_id,
> entry->gfp_flags = gfp_flags;
> entry->node = node;
>
> + filter_check_discard(call, entry, event);
> +
> ring_buffer_unlock_commit(tr->buffer, event);
>
> trace_wake_up();
> @@ -71,6 +74,7 @@ static inline void kmemtrace_free(enum kmemtrace_type_id type_id,
> unsigned long call_site,
> const void *ptr)
> {
> + struct ftrace_event_call *call = &event_kmem_free;
> struct trace_array *tr = kmemtrace_array;
> struct kmemtrace_free_entry *entry;
> struct ring_buffer_event *event;
> @@ -86,6 +90,8 @@ static inline void kmemtrace_free(enum kmemtrace_type_id type_id,
> entry->call_site = call_site;
> entry->ptr = ptr;
>
> + filter_check_discard(call, entry, event);
> +
> ring_buffer_unlock_commit(tr->buffer, event);
>
> trace_wake_up();
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index a0174a4..9a10af0 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -907,6 +907,7 @@ trace_function(struct trace_array *tr,
> unsigned long ip, unsigned long parent_ip, unsigned long flags,
> int pc)
> {
> + struct ftrace_event_call *call = &event_function;
> struct ring_buffer_event *event;
> struct ftrace_entry *entry;
>
> @@ -921,6 +922,9 @@ trace_function(struct trace_array *tr,
> entry = ring_buffer_event_data(event);
> entry->ip = ip;
> entry->parent_ip = parent_ip;
> +
> + filter_check_discard(call, entry, event);
> +
> ring_buffer_unlock_commit(tr->buffer, event);
> }
>
> @@ -930,6 +934,7 @@ static int __trace_graph_entry(struct trace_array *tr,
> unsigned long flags,
> int pc)
> {
> + struct ftrace_event_call *call = &event_funcgraph_entry;
> struct ring_buffer_event *event;
> struct ftrace_graph_ent_entry *entry;
>
> @@ -942,6 +947,7 @@ static int __trace_graph_entry(struct trace_array *tr,
> return 0;
> entry = ring_buffer_event_data(event);
> entry->graph_ent = *trace;
> + filter_check_discard(call, entry, event);
I still wonder a bit about this one and __trace_graph_return.
We had some hangs with the function graph tracer by the past because
it's a slow machine and once we add something that slows it more, it can
make a box spending all its time to service the timer interrupt :-)
I think it will not be a problem for one filter, but may be it could
when we have more. Anyway, this is just a matter of testing and if it hangs
we will just have to limit the number of possible filters.
Thanks,
Frederic.
> ring_buffer_unlock_commit(global_trace.buffer, event);
>
> return 1;
> @@ -952,6 +958,7 @@ static void __trace_graph_return(struct trace_array *tr,
> unsigned long flags,
> int pc)
> {
> + struct ftrace_event_call *call = &event_funcgraph_exit;
> struct ring_buffer_event *event;
> struct ftrace_graph_ret_entry *entry;
>
> @@ -964,6 +971,7 @@ static void __trace_graph_return(struct trace_array *tr,
> return;
> entry = ring_buffer_event_data(event);
> entry->ret = *trace;
> + filter_check_discard(call, entry, event);
> ring_buffer_unlock_commit(global_trace.buffer, event);
> }
> #endif
> @@ -982,6 +990,7 @@ static void __ftrace_trace_stack(struct trace_array *tr,
> int skip, int pc)
> {
> #ifdef CONFIG_STACKTRACE
> + struct ftrace_event_call *call = &event_kernel_stack;
> struct ring_buffer_event *event;
> struct stack_entry *entry;
> struct stack_trace trace;
> @@ -999,6 +1008,7 @@ static void __ftrace_trace_stack(struct trace_array *tr,
> trace.entries = entry->caller;
>
> save_stack_trace(&trace);
> + filter_check_discard(call, entry, event);
> ring_buffer_unlock_commit(tr->buffer, event);
> #endif
> }
> @@ -1024,6 +1034,7 @@ static void ftrace_trace_userstack(struct trace_array *tr,
> unsigned long flags, int pc)
> {
> #ifdef CONFIG_STACKTRACE
> + struct ftrace_event_call *call = &event_user_stack;
> struct ring_buffer_event *event;
> struct userstack_entry *entry;
> struct stack_trace trace;
> @@ -1045,6 +1056,7 @@ static void ftrace_trace_userstack(struct trace_array *tr,
> trace.entries = entry->caller;
>
> save_stack_trace_user(&trace);
> + filter_check_discard(call, entry, event);
> ring_buffer_unlock_commit(tr->buffer, event);
> #endif
> }
> @@ -1061,6 +1073,7 @@ ftrace_trace_special(void *__tr,
> unsigned long arg1, unsigned long arg2, unsigned long arg3,
> int pc)
> {
> + struct ftrace_event_call *call = &event_special;
> struct ring_buffer_event *event;
> struct trace_array *tr = __tr;
> struct special_entry *entry;
> @@ -1073,6 +1086,7 @@ ftrace_trace_special(void *__tr,
> entry->arg1 = arg1;
> entry->arg2 = arg2;
> entry->arg3 = arg3;
> + filter_check_discard(call, entry, event);
> trace_buffer_unlock_commit(tr, event, 0, pc);
> }
>
> @@ -1089,6 +1103,7 @@ tracing_sched_switch_trace(struct trace_array *tr,
> struct task_struct *next,
> unsigned long flags, int pc)
> {
> + struct ftrace_event_call *call = &event_context_switch;
> struct ring_buffer_event *event;
> struct ctx_switch_entry *entry;
>
> @@ -1104,6 +1119,9 @@ tracing_sched_switch_trace(struct trace_array *tr,
> entry->next_prio = next->prio;
> entry->next_state = next->state;
> entry->next_cpu = task_cpu(next);
> +
> + filter_check_discard(call, entry, event);
> +
> trace_buffer_unlock_commit(tr, event, flags, pc);
> }
>
> @@ -1113,6 +1131,7 @@ tracing_sched_wakeup_trace(struct trace_array *tr,
> struct task_struct *curr,
> unsigned long flags, int pc)
> {
> + struct ftrace_event_call *call = &event_wakeup;
> struct ring_buffer_event *event;
> struct ctx_switch_entry *entry;
>
> @@ -1129,6 +1148,8 @@ tracing_sched_wakeup_trace(struct trace_array *tr,
> entry->next_state = wakee->state;
> entry->next_cpu = task_cpu(wakee);
>
> + filter_check_discard(call, entry, event);
> +
> ring_buffer_unlock_commit(tr->buffer, event);
> ftrace_trace_stack(tr, flags, 6, pc);
> ftrace_trace_userstack(tr, flags, pc);
> @@ -1230,6 +1251,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
> (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
> static u32 trace_buf[TRACE_BUF_SIZE];
>
> + struct ftrace_event_call *call = &event_bprint;
> struct ring_buffer_event *event;
> struct trace_array *tr = &global_trace;
> struct trace_array_cpu *data;
> @@ -1269,6 +1291,7 @@ int trace_vbprintk(unsigned long ip, const char *fmt, va_list args)
> entry->fmt = fmt;
>
> memcpy(entry->buf, trace_buf, sizeof(u32) * len);
> + filter_check_discard(call, entry, event);
> ring_buffer_unlock_commit(tr->buffer, event);
>
> out_unlock:
> @@ -1288,6 +1311,7 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
> static raw_spinlock_t trace_buf_lock = __RAW_SPIN_LOCK_UNLOCKED;
> static char trace_buf[TRACE_BUF_SIZE];
>
> + struct ftrace_event_call *call = &event_print;
> struct ring_buffer_event *event;
> struct trace_array *tr = &global_trace;
> struct trace_array_cpu *data;
> @@ -1323,6 +1347,7 @@ int trace_vprintk(unsigned long ip, const char *fmt, va_list args)
>
> memcpy(&entry->buf, trace_buf, len);
> entry->buf[len] = 0;
> + filter_check_discard(call, entry, event);
> ring_buffer_unlock_commit(tr->buffer, event);
>
> out_unlock:
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index cbc168f..e1615d9 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -858,6 +858,21 @@ extern void filter_free_subsystem_preds(struct event_subsystem *system);
> extern int filter_add_subsystem_pred(struct event_subsystem *system,
> struct filter_pred *pred);
>
> +static inline void
> +filter_check_discard(struct ftrace_event_call *call, void *rec,
> + struct ring_buffer_event *event)
> +{
> + if (unlikely(call->preds) && !filter_match_preds(call, rec))
> + ring_buffer_event_discard(event);
> +}
> +
> +#define __common_field(type, item) \
> + ret = trace_define_field(event_call, #type, "common_" #item, \
> + offsetof(typeof(field.ent), item), \
> + sizeof(field.ent.item)); \
> + if (ret) \
> + return ret;
> +
> void event_trace_printk(unsigned long ip, const char *fmt, ...);
> extern struct ftrace_event_call __start_ftrace_events[];
> extern struct ftrace_event_call __stop_ftrace_events[];
> @@ -889,4 +904,9 @@ do { \
> __trace_printk(ip, fmt, ##args); \
> } while (0)
>
> +#undef TRACE_EVENT_FORMAT
> +#define TRACE_EVENT_FORMAT(call, proto, args, fmt, tstruct, tpfmt) \
> + extern struct ftrace_event_call event_##call;
> +#include "trace_event_types.h"
> +
> #endif /* _LINUX_KERNEL_TRACE_H */
> diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
> index ad8c22e..25e618a 100644
> --- a/kernel/trace/trace_branch.c
> +++ b/kernel/trace/trace_branch.c
> @@ -30,6 +30,7 @@ static struct trace_array *branch_tracer;
> static void
> probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
> {
> + struct ftrace_event_call *call = &event_branch;
> struct trace_array *tr = branch_tracer;
> struct ring_buffer_event *event;
> struct trace_branch *entry;
> @@ -73,6 +74,8 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
> entry->line = f->line;
> entry->correct = val == expect;
>
> + filter_check_discard(call, entry, event);
> +
> ring_buffer_unlock_commit(tr->buffer, event);
>
> out:
> diff --git a/kernel/trace/trace_event_types.h b/kernel/trace/trace_event_types.h
> index fd78bee..95b147a 100644
> --- a/kernel/trace/trace_event_types.h
> +++ b/kernel/trace/trace_event_types.h
> @@ -122,8 +122,10 @@ TRACE_EVENT_FORMAT(print, TRACE_PRINT, print_entry, ignore,
> TRACE_EVENT_FORMAT(branch, TRACE_BRANCH, trace_branch, ignore,
> TRACE_STRUCT(
> TRACE_FIELD(unsigned int, line, line)
> - TRACE_FIELD_SPECIAL(char func[TRACE_FUNC_SIZE+1], func, func)
> - TRACE_FIELD_SPECIAL(char file[TRACE_FUNC_SIZE+1], file, file)
> + TRACE_FIELD_SPECIAL(char func[TRACE_FUNC_SIZE+1], func,
> + TRACE_FUNC_SIZE+1, func)
> + TRACE_FIELD_SPECIAL(char file[TRACE_FUNC_SIZE+1], file,
> + TRACE_FUNC_SIZE+1, file)
> TRACE_FIELD(char, correct, correct)
> ),
> TP_RAW_FMT("%u:%s:%s (%u)")
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 64ec4d2..be9299a 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -680,6 +680,7 @@ static struct dentry *
> event_subsystem_dir(const char *name, struct dentry *d_events)
> {
> struct event_subsystem *system;
> + struct dentry *entry;
>
> /* First see if we did not already create this dir */
> list_for_each_entry(system, &event_subsystems, list) {
> @@ -708,6 +709,12 @@ event_subsystem_dir(const char *name, struct dentry *d_events)
>
> system->preds = NULL;
>
> + entry = debugfs_create_file("filter", 0644, system->entry, system,
> + &ftrace_subsystem_filter_fops);
> + if (!entry)
> + pr_warning("Could not create debugfs "
> + "'%s/filter' entry\n", name);
> +
> return system->entry;
> }
>
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index 026be41..470ad94 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -185,7 +185,7 @@ void filter_free_subsystem_preds(struct event_subsystem *system)
> }
>
> events_for_each(call) {
> - if (!call->name || !call->regfunc)
> + if (!call->define_fields)
> continue;
>
> if (!strcmp(call->system, system->name))
> @@ -324,7 +324,7 @@ int filter_add_subsystem_pred(struct event_subsystem *system,
> events_for_each(call) {
> int err;
>
> - if (!call->name || !call->regfunc)
> + if (!call->define_fields)
> continue;
>
> if (strcmp(call->system, system->name))
> diff --git a/kernel/trace/trace_events_stage_2.h b/kernel/trace/trace_events_stage_2.h
> index 30743f7..1c94b87 100644
> --- a/kernel/trace/trace_events_stage_2.h
> +++ b/kernel/trace/trace_events_stage_2.h
> @@ -146,13 +146,6 @@ ftrace_format_##call(struct trace_seq *s) \
> if (ret) \
> return ret;
>
> -#define __common_field(type, item) \
> - ret = trace_define_field(event_call, #type, "common_" #item, \
> - offsetof(typeof(field.ent), item), \
> - sizeof(field.ent.item)); \
> - if (ret) \
> - return ret;
> -
> #undef TRACE_EVENT
> #define TRACE_EVENT(call, proto, args, tstruct, func, print) \
> int \
> diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c
> index 4d9952d..47989be 100644
> --- a/kernel/trace/trace_export.c
> +++ b/kernel/trace/trace_export.c
> @@ -30,7 +30,7 @@
>
>
> #undef TRACE_FIELD_SPECIAL
> -#define TRACE_FIELD_SPECIAL(type_item, item, cmd) \
> +#define TRACE_FIELD_SPECIAL(type_item, item, len, cmd) \
> ret = trace_seq_printf(s, "\tfield special:" #type_item ";\t" \
> "offset:%u;\tsize:%u;\n", \
> (unsigned int)offsetof(typeof(field), item), \
> @@ -85,18 +85,69 @@ ftrace_format_##call(struct trace_seq *s) \
> #define TRACE_ENTRY entry
>
> #undef TRACE_FIELD_SPECIAL
> -#define TRACE_FIELD_SPECIAL(type_item, item, cmd) \
> +#define TRACE_FIELD_SPECIAL(type_item, item, len, cmd) \
> cmd;
>
> #undef TRACE_EVENT_FORMAT
> #define TRACE_EVENT_FORMAT(call, proto, args, fmt, tstruct, tpfmt) \
> +int ftrace_define_fields_##call(void); \
> +static int ftrace_raw_init_event_##call(void); \
> \
> -static struct ftrace_event_call __used \
> +struct ftrace_event_call __used \
> __attribute__((__aligned__(4))) \
> __attribute__((section("_ftrace_events"))) event_##call = { \
> .name = #call, \
> .id = proto, \
> .system = __stringify(TRACE_SYSTEM), \
> + .raw_init = ftrace_raw_init_event_##call, \
> .show_format = ftrace_format_##call, \
> + .define_fields = ftrace_define_fields_##call, \
> +}; \
> +static int ftrace_raw_init_event_##call(void) \
> +{ \
> + INIT_LIST_HEAD(&event_##call.fields); \
> + return 0; \
> +} \
> +
> +#include "trace_event_types.h"
> +
> +#undef TRACE_FIELD
> +#define TRACE_FIELD(type, item, assign) \
> + ret = trace_define_field(event_call, #type, #item, \
> + offsetof(typeof(field), item), \
> + sizeof(field.item)); \
> + if (ret) \
> + return ret;
> +
> +#undef TRACE_FIELD_SPECIAL
> +#define TRACE_FIELD_SPECIAL(type, item, len, cmd) \
> + ret = trace_define_field(event_call, #type "[" #len "]", #item, \
> + offsetof(typeof(field), item), \
> + sizeof(field.item)); \
> + if (ret) \
> + return ret;
> +
> +#undef TRACE_FIELD_ZERO_CHAR
> +#define TRACE_FIELD_ZERO_CHAR(item)
> +
> +#undef TRACE_EVENT_FORMAT
> +#define TRACE_EVENT_FORMAT(call, proto, args, fmt, tstruct, tpfmt) \
> +int \
> +ftrace_define_fields_##call(void) \
> +{ \
> + struct ftrace_event_call *event_call = &event_##call; \
> + struct args field; \
> + int ret; \
> + \
> + __common_field(unsigned char, type); \
> + __common_field(unsigned char, flags); \
> + __common_field(unsigned char, preempt_count); \
> + __common_field(int, pid); \
> + __common_field(int, tgid); \
> + \
> + tstruct; \
> + \
> + return ret; \
> }
> +
> #include "trace_event_types.h"
> diff --git a/kernel/trace/trace_hw_branches.c b/kernel/trace/trace_hw_branches.c
> index 7bfdf4c..e6b275b 100644
> --- a/kernel/trace/trace_hw_branches.c
> +++ b/kernel/trace/trace_hw_branches.c
> @@ -168,6 +168,7 @@ static enum print_line_t bts_trace_print_line(struct trace_iterator *iter)
>
> void trace_hw_branch(u64 from, u64 to)
> {
> + struct ftrace_event_call *call = &event_hw_branch;
> struct trace_array *tr = hw_branch_trace;
> struct ring_buffer_event *event;
> struct hw_branch_entry *entry;
> @@ -194,6 +195,7 @@ void trace_hw_branch(u64 from, u64 to)
> entry->ent.type = TRACE_HW_BRANCHES;
> entry->from = from;
> entry->to = to;
> + filter_check_discard(call, entry, event);
> trace_buffer_unlock_commit(tr, event, 0, 0);
>
> out:
> diff --git a/kernel/trace/trace_power.c b/kernel/trace/trace_power.c
> index bae791e..8ce7d7d 100644
> --- a/kernel/trace/trace_power.c
> +++ b/kernel/trace/trace_power.c
> @@ -36,6 +36,7 @@ static void probe_power_start(struct power_trace *it, unsigned int type,
>
> static void probe_power_end(struct power_trace *it)
> {
> + struct ftrace_event_call *call = &event_power;
> struct ring_buffer_event *event;
> struct trace_power *entry;
> struct trace_array_cpu *data;
> @@ -54,6 +55,7 @@ static void probe_power_end(struct power_trace *it)
> goto out;
> entry = ring_buffer_event_data(event);
> entry->state_data = *it;
> + filter_check_discard(call, entry, event);
> trace_buffer_unlock_commit(tr, event, 0, 0);
> out:
> preempt_enable();
> @@ -62,6 +64,7 @@ static void probe_power_end(struct power_trace *it)
> static void probe_power_mark(struct power_trace *it, unsigned int type,
> unsigned int level)
> {
> + struct ftrace_event_call *call = &event_power;
> struct ring_buffer_event *event;
> struct trace_power *entry;
> struct trace_array_cpu *data;
> @@ -84,6 +87,7 @@ static void probe_power_mark(struct power_trace *it, unsigned int type,
> goto out;
> entry = ring_buffer_event_data(event);
> entry->state_data = *it;
> + filter_check_discard(call, entry, event);
> trace_buffer_unlock_commit(tr, event, 0, 0);
> out:
> preempt_enable();
> --
> 1.6.2.1
>
> --
--
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