Adding new control events to enable/disable specific event.
The interface string for control file are:

  'enable-<EVENT NAME>'
  'disable-<EVENT NAME>'

when received the command, perf will scan the current evlist
for <EVENT NAME> and if found it's enabled/disabled.

Example session:

  terminal 1:
    # mkfifo control ack perf.pipe
    # perf record --control=fifo:control,ack -D -1 --no-buffering -e 'sched:*' 
-o - > perf.pipe
    Events disabled

  terminal 2:
    # cat perf.pipe | ./perf --no-pager script -i -

  terminal 3:
    # echo enable-sched:sched_process_fork > control

  terminal 1:
    # mkfifo control ack perf.pipe
    # perf record --control=fifo:control,ack -D -1 --no-buffering -e 'sched:*' 
-o - > perf.pipe
    ...
    event sched:sched_process_fork enabled

  terminal 2:
    # cat perf.pipe | ./perf --no-pager script -i -
    bash 33349 [034] 149587.674295: sched:sched_process_fork: comm=bash 
pid=33349 child_comm=bash child_pid=34056
    bash 33349 [034] 149588.239521: sched:sched_process_fork: comm=bash 
pid=33349 child_comm=bash child_pid=34057

  terminal 3:
    # echo enable-sched:sched_wakeup_new > control

  terminal 1:
    # mkfifo control ack perf.pipe
    # perf record --control=fifo:control,ack -D -1 --no-buffering -e 'sched:*' 
-o - > perf.pipe
    ...
    event sched:sched_wakeup_new enabled

  terminal 2:
    # cat perf.pipe | ./perf --no-pager script -i -
    ...
    bash 33349 [034] 149632.228023: sched:sched_process_fork: comm=bash 
pid=33349 child_comm=bash child_pid=34059
    bash 33349 [034] 149632.228050:   sched:sched_wakeup_new: bash:34059 [120] 
success=1 CPU:036
    bash 33349 [034] 149633.950005: sched:sched_process_fork: comm=bash 
pid=33349 child_comm=bash child_pid=34060
    bash 33349 [034] 149633.950030:   sched:sched_wakeup_new: bash:34060 [120] 
success=1 CPU:036

Signed-off-by: Jiri Olsa <jo...@kernel.org>
---
 tools/perf/builtin-record.c |  2 ++
 tools/perf/builtin-stat.c   |  2 ++
 tools/perf/util/evlist.c    | 30 +++++++++++++++++++++++++++++-
 tools/perf/util/evlist.h    |  4 ++++
 4 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index d832c108a1ca..582b8fba012c 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1949,6 +1949,8 @@ static int __cmd_record(struct record *rec, int argc, 
const char **argv)
                                break;
                        case EVLIST_CTL_CMD_ACK:
                        case EVLIST_CTL_CMD_UNSUPPORTED:
+                       case EVLIST_CTL_CMD_ENABLE_EVSEL:
+                       case EVLIST_CTL_CMD_DISABLE_EVSEL:
                        default:
                                break;
                        }
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 89c32692f40c..6a21fb665008 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -590,6 +590,8 @@ static void process_evlist(struct evlist *evlist, unsigned 
int interval)
                case EVLIST_CTL_CMD_SNAPSHOT:
                case EVLIST_CTL_CMD_ACK:
                case EVLIST_CTL_CMD_UNSUPPORTED:
+               case EVLIST_CTL_CMD_ENABLE_EVSEL:
+               case EVLIST_CTL_CMD_DISABLE_EVSEL:
                default:
                        break;
                }
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 70aff26612a9..05723227bebf 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1915,7 +1915,13 @@ static int evlist__ctlfd_recv(struct evlist *evlist, 
enum evlist_ctl_cmd *cmd,
                 bytes_read == data_size ? "" : c == '\n' ? "\\n" : "\\0");
 
        if (bytes_read > 0) {
-               if (!strncmp(cmd_data, EVLIST_CTL_CMD_ENABLE_TAG,
+               if (!strncmp(cmd_data, EVLIST_CTL_CMD_ENABLE_EVSEL_TAG,
+                                   
(sizeof(EVLIST_CTL_CMD_ENABLE_EVSEL_TAG)-1))) {
+                       *cmd = EVLIST_CTL_CMD_ENABLE_EVSEL;
+               } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_DISABLE_EVSEL_TAG,
+                                   
(sizeof(EVLIST_CTL_CMD_DISABLE_EVSEL_TAG)-1))) {
+                       *cmd = EVLIST_CTL_CMD_DISABLE_EVSEL;
+               } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_ENABLE_TAG,
                             (sizeof(EVLIST_CTL_CMD_ENABLE_TAG)-1))) {
                        *cmd = EVLIST_CTL_CMD_ENABLE;
                } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_DISABLE_TAG,
@@ -1952,6 +1958,8 @@ int evlist__ctlfd_process(struct evlist *evlist, enum 
evlist_ctl_cmd *cmd)
        char cmd_data[EVLIST_CTL_CMD_MAX_LEN];
        int ctlfd_pos = evlist->ctl_fd.pos;
        struct pollfd *entries = evlist->core.pollfd.entries;
+       struct evsel *evsel;
+       char *evsel_name;
 
        if (!evlist__ctlfd_initialized(evlist) || !entries[ctlfd_pos].revents)
                return 0;
@@ -1967,6 +1975,26 @@ int evlist__ctlfd_process(struct evlist *evlist, enum 
evlist_ctl_cmd *cmd)
                        case EVLIST_CTL_CMD_DISABLE:
                                evlist__disable(evlist);
                                break;
+                       case EVLIST_CTL_CMD_ENABLE_EVSEL:
+                               evsel_name = cmd_data + 
sizeof(EVLIST_CTL_CMD_ENABLE_EVSEL_TAG) - 1;
+                               evsel = evlist__find_evsel_by_str(evlist, 
evsel_name);
+                               if (evsel) {
+                                       evlist__enable_evsel(evlist, 
evsel_name);
+                                       pr_info("event %s enabled\n", 
evsel->name);
+                               } else {
+                                       pr_info("failed: can't find %s 
event\n", evsel_name);
+                               }
+                               break;
+                       case EVLIST_CTL_CMD_DISABLE_EVSEL:
+                               evsel_name = cmd_data + 
sizeof(EVLIST_CTL_CMD_DISABLE_EVSEL_TAG) - 1;
+                               evsel = evlist__find_evsel_by_str(evlist, 
evsel_name);
+                               if (evsel) {
+                                       evlist__disable_evsel(evlist, 
evsel_name);
+                                       pr_info("event %s disabled\n", 
evsel->name);
+                               } else {
+                                       pr_info("failed: can't find %s 
event\n", evsel_name);
+                               }
+                               break;
                        case EVLIST_CTL_CMD_SNAPSHOT:
                                break;
                        case EVLIST_CTL_CMD_ACK:
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 1aae75895dea..e4e8ff8831a3 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -330,6 +330,8 @@ struct evsel *evlist__reset_weak_group(struct evlist 
*evlist, struct evsel *evse
 #define EVLIST_CTL_CMD_DISABLE_TAG "disable"
 #define EVLIST_CTL_CMD_ACK_TAG     "ack\n"
 #define EVLIST_CTL_CMD_SNAPSHOT_TAG "snapshot"
+#define EVLIST_CTL_CMD_ENABLE_EVSEL_TAG "enable-"
+#define EVLIST_CTL_CMD_DISABLE_EVSEL_TAG "disable-"
 
 #define EVLIST_CTL_CMD_MAX_LEN 64
 
@@ -337,6 +339,8 @@ enum evlist_ctl_cmd {
        EVLIST_CTL_CMD_UNSUPPORTED = 0,
        EVLIST_CTL_CMD_ENABLE,
        EVLIST_CTL_CMD_DISABLE,
+       EVLIST_CTL_CMD_ENABLE_EVSEL,
+       EVLIST_CTL_CMD_DISABLE_EVSEL,
        EVLIST_CTL_CMD_ACK,
        EVLIST_CTL_CMD_SNAPSHOT,
 };
-- 
2.26.2

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