Messages in this thread Patch in this message | | | From | Frederic Weisbecker <> | Subject | [PATCH] tracing/lockdep: turn lock->name into an array | Date | Tue, 14 Apr 2009 00:36:06 +0200 |
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Impact: allow filtering by lock name / fix module tracing
Currently, the "lock acquired" event is traced using a TRACE_EVENT. But we can't use the char * type for the name without risking to dereference a freed pointer. A lock name can come from a module towards lockdep and it is risky to only store its address because we defer its name printing.
That's why this patch uses a fixed array size and copy the name. Also it lets us filter the lock name because the event filtering doesn't handle the char pointers. Such support is not needed yet since the events don't use it for now because it is rarely easy to keep track of a string while we defer its output.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> --- include/trace/lockdep_event_types.h | 13 +++++++++++-- 1 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/include/trace/lockdep_event_types.h b/include/trace/lockdep_event_types.h index 863f1e4..68f84f4 100644 --- a/include/trace/lockdep_event_types.h +++ b/include/trace/lockdep_event_types.h @@ -32,18 +32,27 @@ TRACE_FORMAT(lock_contended, TP_FMT("%s", lock->name) ); +#define LOCK_NAME_SIZE 25 + +/* + * We might loose the name if it comes from a module + * so we keep a fixed array size of 25, enough for most + * usecases. + */ + TRACE_EVENT(lock_acquired, TP_PROTO(struct lockdep_map *lock, unsigned long ip, s64 waittime), TP_ARGS(lock, ip, waittime), TP_STRUCT__entry( - __field(const char *, name) + __array(char, name, LOCK_NAME_SIZE) __field(unsigned long, wait_usec) __field(unsigned long, wait_nsec_rem) ), TP_fast_assign( - __entry->name = lock->name; + strncpy(__entry->name, lock->name, LOCK_NAME_SIZE - 1); + __entry->name[LOCK_NAME_SIZE - 1] = 0; __entry->wait_nsec_rem = do_div(waittime, NSEC_PER_USEC); __entry->wait_usec = (unsigned long) waittime; ), -- 1.6.1
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