From 042957801626465492b9428860de39a3cb2a8219 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 12 Nov 2010 22:32:11 -0500 Subject: tracing/events: Show real number in array fields Currently we have in something like the sched_switch event: field:char prev_comm[TASK_COMM_LEN]; offset:12; size:16; signed:1; When a userspace tool such as perf tries to parse this, the TASK_COMM_LEN is meaningless. This is done because the TRACE_EVENT() macro simply uses a #len to show the string of the length. When the length is an enum, we get a string that means nothing for tools. By adding a static buffer and a mutex to protect it, we can store the string into that buffer with snprintf and show the actual number. Now we get: field:char prev_comm[16]; offset:12; size:16; signed:1; Something much more useful. Signed-off-by: Steven Rostedt --- kernel/trace/trace_export.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) (limited to 'kernel/trace/trace_export.c') diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c index 4ba44deaac25..4b74d71705c0 100644 --- a/kernel/trace/trace_export.c +++ b/kernel/trace/trace_export.c @@ -83,13 +83,19 @@ static void __always_unused ____ftrace_check_##name(void) \ #undef __array #define __array(type, item, len) \ - BUILD_BUG_ON(len > MAX_FILTER_STR_VAL); \ - ret = trace_define_field(event_call, #type "[" #len "]", #item, \ + do { \ + BUILD_BUG_ON(len > MAX_FILTER_STR_VAL); \ + mutex_lock(&event_storage_mutex); \ + snprintf(event_storage, sizeof(event_storage), \ + "%s[%d]", #type, len); \ + ret = trace_define_field(event_call, event_storage, #item, \ offsetof(typeof(field), item), \ sizeof(field.item), \ is_signed_type(type), FILTER_OTHER); \ - if (ret) \ - return ret; + mutex_unlock(&event_storage_mutex); \ + if (ret) \ + return ret; \ + } while (0); #undef __array_desc #define __array_desc(type, container, item, len) \ -- cgit v1.2.2 From e4a9ea5ee7c8812a7bf0c3fb725ceeaa3d4c2fcc Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Thu, 27 Jan 2011 09:15:30 -0500 Subject: tracing: Replace trace_event struct array with pointer array Currently the trace_event structures are placed in the _ftrace_events section, and at link time, the linker makes one large array of all the trace_event structures. On boot up, this array is read (much like the initcall sections) and the events are processed. The problem is that there is no guarantee that gcc will place complex structures nicely together in an array format. Two structures in the same file may be placed awkwardly, because gcc has no clue that they are suppose to be in an array. A hack was used previous to force the alignment to 4, to pack the structures together. But this caused alignment issues with other architectures (sparc). Instead of packing the structures into an array, the structures' addresses are now put into the _ftrace_event section. As pointers are always the natural alignment, gcc should always pack them tightly together (otherwise initcall, extable, etc would also fail). By having the pointers to the structures in the section, we can still iterate the trace_events without causing unnecessary alignment problems with other architectures, or depending on the current behaviour of gcc that will likely change in the future just to tick us kernel developers off a little more. The _ftrace_event section is also moved into the .init.data section as it is now only needed at boot up. Suggested-by: David Miller Cc: Mathieu Desnoyers Acked-by: David S. Miller Signed-off-by: Steven Rostedt --- kernel/trace/trace_export.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'kernel/trace/trace_export.c') diff --git a/kernel/trace/trace_export.c b/kernel/trace/trace_export.c index 4b74d71705c0..bbeec31e0ae3 100644 --- a/kernel/trace/trace_export.c +++ b/kernel/trace/trace_export.c @@ -161,13 +161,13 @@ struct ftrace_event_class event_class_ftrace_##call = { \ .fields = LIST_HEAD_INIT(event_class_ftrace_##call.fields),\ }; \ \ -struct ftrace_event_call __used \ -__attribute__((__aligned__(4))) \ -__attribute__((section("_ftrace_events"))) event_##call = { \ +struct ftrace_event_call __used event_##call = { \ .name = #call, \ .event.type = etype, \ .class = &event_class_ftrace_##call, \ .print_fmt = print, \ }; \ +struct ftrace_event_call __used \ +__attribute__((section("_ftrace_events"))) *__event_##call = &event_##call; #include "trace_entries.h" -- cgit v1.2.2