Merge tag 'perf-urgent-for-mingo-5.3-20190708-2' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/core

Pull perf/urgent fixes from Arnaldo Carvalho de Melo:

core:

  Arnaldo Carvalho de Melo:

  - Allow references to thread objects after__machine_exit(), fixing a bug with
    'perf sched lat' where that happens, i.e. after perf_session__delete() we
    still have references to threads that were in a linked list whose head was
    freed in perf_session__delete(), causing a segfault, fix it.

  Jiri Olsa:

  - Do not rely on errno values for precise_ip fallback, fixing the default
    use case for 'perf record' on some AMD servers, when no events are specified
    and we try to use "cycles:P", i.e. with the maximum precision level.

BPF:

  Song Liu:

  - Assign proper ff->ph in perf_event__synthesize_features(), fixing a bug
    when using pipe mode, i.e.  'perf record -o -'.

tools headers:

  Arnaldo Carvalho de Melo:

  - Sync kvm headers with the kernel sources

perf tests:

  Seeteena Thoufeek:

  - Fix record+probe_libc_inet_pton.sh for powerpc64, where without the
    debuginfo package for the 'ping' utility we can't resolve its symbols,
    so admit getting "[unknown]" for that backtrace line.

perf python:

  Arnaldo Carvalho de Melo:

  - Remove -fstack-protector-strong if clang doesn't have it, fixing the build
    with clang on fedora:30, oracleline:7, centos:7.

perf jvmti:

  Jiri Olsa:

  - Address gcc string overflow warning for strncpy()

build:

  Arnaldo Carvalho de Melo:

  - Check if gettid() is available before providing helper, as recent
    versions of glibc started to provide gettid().

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 23 insertions, 2 deletions

diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
index 1b3d7265bca9..147ed85ea2bc 100644
--- a/tools/perf/util/machine.c
+++ b/tools/perf/util/machine.c
@@ -210,6 +210,18 @@ void machine__exit(struct machine *machine)
 
 	for (i = 0; i < THREADS__TABLE_SIZE; i++) {
 		struct threads *threads = &machine->threads[i];
+		struct thread *thread, *n;
+		/*
+		 * Forget about the dead, at this point whatever threads were
+		 * left in the dead lists better have a reference count taken
+		 * by who is using them, and then, when they drop those references
+		 * and it finally hits zero, thread__put() will check and see that
+		 * its not in the dead threads list and will not try to remove it
+		 * from there, just calling thread__delete() straight away.
+		 */
+		list_for_each_entry_safe(thread, n, &threads->dead, node)
+			list_del_init(&thread->node);
+
 		exit_rwsem(&threads->lock);
 	}
 }
@@ -1759,9 +1771,11 @@ static void __machine__remove_thread(struct machine *machine, struct thread *th,
 	if (threads->last_match == th)
 		threads__set_last_match(threads, NULL);
 
-	BUG_ON(refcount_read(&th->refcnt) == 0);
 	if (lock)
 		down_write(&threads->lock);
+
+	BUG_ON(refcount_read(&th->refcnt) == 0);
+
 	rb_erase_cached(&th->rb_node, &threads->entries);
 	RB_CLEAR_NODE(&th->rb_node);
 	--threads->nr;
@@ -1771,9 +1785,16 @@ static void __machine__remove_thread(struct machine *machine, struct thread *th,
 	 * will be called and we will remove it from the dead_threads list.
 	 */
 	list_add_tail(&th->node, &threads->dead);
+
+	/*
+	 * We need to do the put here because if this is the last refcount,
+	 * then we will be touching the threads->dead head when removing the
+	 * thread.
+	 */
+	thread__put(th);
+
 	if (lock)
 		up_write(&threads->lock);
-	thread__put(th);
 }
 
 void machine__remove_thread(struct machine *machine, struct thread *th)