From fc800a10be26017f8f338bc8e500d48e3e6429d9 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Mon, 5 Nov 2018 18:00:43 +0900 Subject: tracing: Lock event_mutex before synth_event_mutex synthetic event is using synth_event_mutex for protecting synth_event_list, and event_trigger_write() path acquires locks as below order. event_trigger_write(event_mutex) ->trigger_process_regex(trigger_cmd_mutex) ->event_hist_trigger_func(synth_event_mutex) On the other hand, synthetic event creation and deletion paths call trace_add_event_call() and trace_remove_event_call() which acquires event_mutex. In that case, if we keep the synth_event_mutex locked while registering/unregistering synthetic events, its dependency will be inversed. To avoid this issue, current synthetic event is using a 2 phase process to create/delete events. For example, it searches existing events under synth_event_mutex to check for event-name conflicts, and unlocks synth_event_mutex, then registers a new event under event_mutex locked. Finally, it locks synth_event_mutex and tries to add the new event to the list. But it can introduce complexity and a chance for name conflicts. To solve this simpler, this introduces trace_add_event_call_nolock() and trace_remove_event_call_nolock() which don't acquire event_mutex inside. synthetic event can lock event_mutex before synth_event_mutex to solve the lock dependency issue simpler. Link: http://lkml.kernel.org/r/154140844377.17322.13781091165954002713.stgit@devbox Reviewed-by: Tom Zanussi Tested-by: Tom Zanussi Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_events.c | 34 ++++++++++++++++++++++++++++------ 1 file changed, 28 insertions(+), 6 deletions(-) (limited to 'kernel/trace/trace_events.c') diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index f94be0c2827b..a3b157f689ee 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2305,11 +2305,11 @@ __trace_early_add_new_event(struct trace_event_call *call, struct ftrace_module_file_ops; static void __add_event_to_tracers(struct trace_event_call *call); -/* Add an additional event_call dynamically */ -int trace_add_event_call(struct trace_event_call *call) +int trace_add_event_call_nolock(struct trace_event_call *call) { int ret; - mutex_lock(&event_mutex); + lockdep_assert_held(&event_mutex); + mutex_lock(&trace_types_lock); ret = __register_event(call, NULL); @@ -2317,6 +2317,16 @@ int trace_add_event_call(struct trace_event_call *call) __add_event_to_tracers(call); mutex_unlock(&trace_types_lock); + return ret; +} + +/* Add an additional event_call dynamically */ +int trace_add_event_call(struct trace_event_call *call) +{ + int ret; + + mutex_lock(&event_mutex); + ret = trace_add_event_call_nolock(call); mutex_unlock(&event_mutex); return ret; } @@ -2366,17 +2376,29 @@ static int probe_remove_event_call(struct trace_event_call *call) return 0; } -/* Remove an event_call */ -int trace_remove_event_call(struct trace_event_call *call) +/* no event_mutex version */ +int trace_remove_event_call_nolock(struct trace_event_call *call) { int ret; - mutex_lock(&event_mutex); + lockdep_assert_held(&event_mutex); + mutex_lock(&trace_types_lock); down_write(&trace_event_sem); ret = probe_remove_event_call(call); up_write(&trace_event_sem); mutex_unlock(&trace_types_lock); + + return ret; +} + +/* Remove an event_call */ +int trace_remove_event_call(struct trace_event_call *call) +{ + int ret; + + mutex_lock(&event_mutex); + ret = trace_remove_event_call_nolock(call); mutex_unlock(&event_mutex); return ret; -- cgit v1.2.3-59-g8ed1b From 7e1413edd6194a9807aa5f3ac0378b9b4b9da879 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Tue, 4 Dec 2018 13:35:45 -0500 Subject: tracing: Consolidate trace_add/remove_event_call back to the nolock functions The trace_add/remove_event_call_nolock() functions were added to allow the tace_add/remove_event_call() code be called when the event_mutex lock was already taken. Now that all callers are done within the event_mutex, there's no reason to have two different interfaces. Remove the current wrapper trace_add/remove_event_call()s and rename the _nolock versions back to the original names. Link: http://lkml.kernel.org/r/154140866955.17322.2081425494660638846.stgit@devbox Acked-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware) --- include/linux/trace_events.h | 2 -- kernel/trace/trace_events.c | 30 ++++-------------------------- kernel/trace/trace_events_hist.c | 6 +++--- kernel/trace/trace_kprobe.c | 4 ++-- kernel/trace/trace_uprobe.c | 4 ++-- 5 files changed, 11 insertions(+), 35 deletions(-) (limited to 'kernel/trace/trace_events.c') diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index 3aa05593a53f..4130a5497d40 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -529,8 +529,6 @@ extern int trace_event_raw_init(struct trace_event_call *call); extern int trace_define_field(struct trace_event_call *call, const char *type, const char *name, int offset, int size, int is_signed, int filter_type); -extern int trace_add_event_call_nolock(struct trace_event_call *call); -extern int trace_remove_event_call_nolock(struct trace_event_call *call); extern int trace_add_event_call(struct trace_event_call *call); extern int trace_remove_event_call(struct trace_event_call *call); extern int trace_event_get_offsets(struct trace_event_call *call); diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index a3b157f689ee..bd0162c0467c 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -2305,7 +2305,8 @@ __trace_early_add_new_event(struct trace_event_call *call, struct ftrace_module_file_ops; static void __add_event_to_tracers(struct trace_event_call *call); -int trace_add_event_call_nolock(struct trace_event_call *call) +/* Add an additional event_call dynamically */ +int trace_add_event_call(struct trace_event_call *call) { int ret; lockdep_assert_held(&event_mutex); @@ -2320,17 +2321,6 @@ int trace_add_event_call_nolock(struct trace_event_call *call) return ret; } -/* Add an additional event_call dynamically */ -int trace_add_event_call(struct trace_event_call *call) -{ - int ret; - - mutex_lock(&event_mutex); - ret = trace_add_event_call_nolock(call); - mutex_unlock(&event_mutex); - return ret; -} - /* * Must be called under locking of trace_types_lock, event_mutex and * trace_event_sem. @@ -2376,8 +2366,8 @@ static int probe_remove_event_call(struct trace_event_call *call) return 0; } -/* no event_mutex version */ -int trace_remove_event_call_nolock(struct trace_event_call *call) +/* Remove an event_call */ +int trace_remove_event_call(struct trace_event_call *call) { int ret; @@ -2392,18 +2382,6 @@ int trace_remove_event_call_nolock(struct trace_event_call *call) return ret; } -/* Remove an event_call */ -int trace_remove_event_call(struct trace_event_call *call) -{ - int ret; - - mutex_lock(&event_mutex); - ret = trace_remove_event_call_nolock(call); - mutex_unlock(&event_mutex); - - return ret; -} - #define for_each_event(event, start, end) \ for (event = start; \ (unsigned long)event < (unsigned long)end; \ diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 21e4954375a1..82e72c48a5a9 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -960,7 +960,7 @@ static int register_synth_event(struct synth_event *event) call->data = event; call->tp = event->tp; - ret = trace_add_event_call_nolock(call); + ret = trace_add_event_call(call); if (ret) { pr_warn("Failed to register synthetic event: %s\n", trace_event_name(call)); @@ -969,7 +969,7 @@ static int register_synth_event(struct synth_event *event) ret = set_synth_event_print_fmt(call); if (ret < 0) { - trace_remove_event_call_nolock(call); + trace_remove_event_call(call); goto err; } out: @@ -984,7 +984,7 @@ static int unregister_synth_event(struct synth_event *event) struct trace_event_call *call = &event->call; int ret; - ret = trace_remove_event_call_nolock(call); + ret = trace_remove_event_call(call); return ret; } diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index bdf8c2ad5152..0e0f7b8024fb 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -1353,7 +1353,7 @@ static int register_kprobe_event(struct trace_kprobe *tk) kfree(call->print_fmt); return -ENODEV; } - ret = trace_add_event_call_nolock(call); + ret = trace_add_event_call(call); if (ret) { pr_info("Failed to register kprobe event: %s\n", trace_event_name(call)); @@ -1368,7 +1368,7 @@ static int unregister_kprobe_event(struct trace_kprobe *tk) int ret; /* tp->event is unregistered in trace_remove_event_call() */ - ret = trace_remove_event_call_nolock(&tk->tp.call); + ret = trace_remove_event_call(&tk->tp.call); if (!ret) kfree(tk->tp.call.print_fmt); return ret; diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c index 4a7b21c891f3..e335576b9411 100644 --- a/kernel/trace/trace_uprobe.c +++ b/kernel/trace/trace_uprobe.c @@ -1320,7 +1320,7 @@ static int register_uprobe_event(struct trace_uprobe *tu) return -ENODEV; } - ret = trace_add_event_call_nolock(call); + ret = trace_add_event_call(call); if (ret) { pr_info("Failed to register uprobe event: %s\n", @@ -1337,7 +1337,7 @@ static int unregister_uprobe_event(struct trace_uprobe *tu) int ret; /* tu->event is unregistered in trace_remove_event_call() */ - ret = trace_remove_event_call_nolock(&tu->tp.call); + ret = trace_remove_event_call(&tu->tp.call); if (ret) return ret; kfree(tu->tp.call.print_fmt); -- cgit v1.2.3-59-g8ed1b From b6b2735514bcd70ad1556a33892a636b20ece671 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Thu, 20 Dec 2018 13:20:07 -0500 Subject: tracing: Use str_has_prefix() instead of using fixed sizes There are several instances of strncmp(str, "const", 123), where 123 is the strlen of the const string to check if "const" is the prefix of str. But this can be error prone. Use str_has_prefix() instead. Acked-by: Namhyung Kim Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace.c | 2 +- kernel/trace/trace_events.c | 2 +- kernel/trace/trace_events_hist.c | 2 +- kernel/trace/trace_probe.c | 4 ++-- kernel/trace/trace_stack.c | 2 +- 5 files changed, 6 insertions(+), 6 deletions(-) (limited to 'kernel/trace/trace_events.c') diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 5afcfecb4bc2..eac2824a18ab 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4411,7 +4411,7 @@ static int trace_set_options(struct trace_array *tr, char *option) cmp = strstrip(option); - if (strncmp(cmp, "no", 2) == 0) { + if (str_has_prefix(cmp, "no")) { neg = 1; cmp += 2; } diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index bd0162c0467c..5b3b0c3c8a47 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -1251,7 +1251,7 @@ static int f_show(struct seq_file *m, void *v) */ array_descriptor = strchr(field->type, '['); - if (!strncmp(field->type, "__data_loc", 10)) + if (str_has_prefix(field->type, "__data_loc")) array_descriptor = NULL; if (!array_descriptor) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 9d590138f870..0d878dcd1e4b 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -518,7 +518,7 @@ static int synth_event_define_fields(struct trace_event_call *call) static bool synth_field_signed(char *type) { - if (strncmp(type, "u", 1) == 0) + if (str_has_prefix(type, "u")) return false; return true; diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index ff86417c0149..541375737403 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -194,7 +194,7 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t, code->op = FETCH_OP_RETVAL; else ret = -EINVAL; - } else if (strncmp(arg, "stack", 5) == 0) { + } else if (str_has_prefix(arg, "stack")) { if (arg[5] == '\0') { code->op = FETCH_OP_STACKP; } else if (isdigit(arg[5])) { @@ -213,7 +213,7 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t, #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API } else if (((flags & TPARG_FL_MASK) == (TPARG_FL_KERNEL | TPARG_FL_FENTRY)) && - strncmp(arg, "arg", 3) == 0) { + str_has_prefix(arg, "arg")) { if (!isdigit(arg[3])) return -EINVAL; ret = kstrtoul(arg + 3, 10, ¶m); diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c index e2a153fc1afc..3641f28c343f 100644 --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -448,7 +448,7 @@ static char stack_trace_filter_buf[COMMAND_LINE_SIZE+1] __initdata; static __init int enable_stacktrace(char *str) { - if (strncmp(str, "_filter=", 8) == 0) + if (str_has_prefix(str, "_filter=")) strncpy(stack_trace_filter_buf, str+8, COMMAND_LINE_SIZE); stack_tracer_enabled = 1; -- cgit v1.2.3-59-g8ed1b