From 073e5fca53d30ffe9e2fc637a001c78b2cdca7dd Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Tue, 26 Apr 2016 12:33:46 -0300 Subject: [PATCH] perf trace: Read thread's COMM from /proc when not set We get notifications for threads that gets created while we're tracing, but for preexisting threads we may end not having synthesized them, like when tracing a 'perf trace' session that will use '--pid' to trace some other thread. And besides we should probably stop synthesizing those records and instead read thread information in a lazy way, i.e. just when we need, like done in this patch: Now the 'pid_t' argument in 'perf_event_open' gets translated to a COMM: # perf trace -e perf_event_open perf stat -e cycles -p 31601 0.027 ( 0.027 ms): perf/23393 perf_event_open(attr_uptr: 0x2fdd0d8, pid: 31601 (abrt-dump-journ), cpu: -1, group_fd: -1, flags: FD_CLOEXEC) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ = 3 ^C And in other syscalls containing pid_t without thread->comm_set at the time of the formatting. Cc: Adrian Hunter Cc: Borislav Petkov Cc: David Ahern Cc: Jiri Olsa Cc: Milian Wolff Cc: Namhyung Kim Cc: Wang Nan Link: http://lkml.kernel.org/n/tip-ioeps6dlwst17d6oozc9shtk@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/trace/beauty/pid.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/tools/perf/trace/beauty/pid.c b/tools/perf/trace/beauty/pid.c index 111ae08d38f1..07486ea65ae3 100644 --- a/tools/perf/trace/beauty/pid.c +++ b/tools/perf/trace/beauty/pid.c @@ -3,9 +3,12 @@ static size_t syscall_arg__scnprintf_pid(char *bf, size_t size, struct syscall_a int pid = arg->val; struct trace *trace = arg->trace; size_t printed = scnprintf(bf, size, "%d", pid); - struct thread *thread = machine__find_thread(trace->host, pid, pid); + struct thread *thread = machine__findnew_thread(trace->host, pid, pid); if (thread != NULL) { + if (!thread->comm_set) + thread__set_comm_from_proc(thread); + if (thread->comm_set) printed += scnprintf(bf + printed, size - printed, " (%s)", thread__comm_str(thread));