Merge tag 'perf-core-for-mingo-4.21-20190103' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/urgent

Pull perf/core improvements and fixes from Arnaldo Carvalho de Melo:

perf c2c:

  Jiri Olsa:

  - Change the default coalesce setup to from '--coalesce pid,iaddr' to just '--coalesce iaddr'.

  - Increase the HITM ratio limit for displayed cachelines.

perf script:

  Andi Kleen:

  - Fix LBR skid dump problems in brstackinsn.

perf trace:

  Arnaldo Carvalho de Melo:

  - Check if the raw_syscalls:sys_{enter,exit} are setup before setting tp filter.

  - Do not hardcode the size of the tracepoint common_ fields.

  - Beautify USBDEFFS_ ioctl commands.

  Colin Ian King:

  - Use correct SECCOMP prefix spelling, "SECOMP_*" -> "SECCOMP_*".

perf python:

  Jiri Olsa:

  - Do not force closing original perf descriptor in evlist.get_pollfd().

tools misc:

  Jiri Olsa:

  - Allow overriding CFLAGS and LDFLAGS.

perf build:

  Stanislav Fomichev:

  - Don't unconditionally link the libbfd feature test to -liberty and -lz

thread-stack:

  Adrian Hunter:

  - Fix processing for the idle task, having a stack per cpu.

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

1 files changed, 7 insertions, 0 deletions

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 78a067777144a..5456c84c7dd13 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1527,6 +1527,13 @@ struct thread *perf_session__findnew(struct perf_session *session, pid_t pid)
 	return machine__findnew_thread(&session->machines.host, -1, pid);
 }
 
+/*
+ * Threads are identified by pid and tid, and the idle task has pid == tid == 0.
+ * So here a single thread is created for that, but actually there is a separate
+ * idle task per cpu, so there should be one 'struct thread' per cpu, but there
+ * is only 1. That causes problems for some tools, requiring workarounds. For
+ * example get_idle_thread() in builtin-sched.c, or thread_stack__per_cpu().
+ */
 int perf_session__register_idle_thread(struct perf_session *session)
 {
 	struct thread *thread;