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/Documentation/perf-record.txt |  8 +--
 tools/perf/builtin-record.c              |  8 +--
 tools/perf/builtin-stat.c                |  2 -
 tools/perf/util/evlist.c                 | 63 ++++++++++++++++++++++--
 4 files changed, 67 insertions(+), 14 deletions(-)

diff --git a/tools/perf/Documentation/perf-record.txt 
b/tools/perf/Documentation/perf-record.txt
index f896c4b791e1..55d2d335b8a8 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -637,9 +637,11 @@ ctl-fifo / ack-fifo are opened and used as ctl-fd / ack-fd 
as follows.
 Listen on ctl-fd descriptor for command to control measurement.
 
 Available commands:
-  'enable'  : enable events
-  'disable' : disable events
-  'snapshot': AUX area tracing snapshot).
+  'enable'       : enable events
+  'disable'      : disable events
+  'enable name'  : enable event 'name'
+  'disable name' : disable event 'name'
+  'snapshot'     : AUX area tracing snapshot).
 
 Measurements can be started with events disabled using --delay=-1 option. 
Optionally
 send control command completion ('ack\n') to ack-fd descriptor to synchronize 
with the
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index d832c108a1ca..e9874832dc27 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1937,18 +1937,14 @@ static int __cmd_record(struct record *rec, int argc, 
const char **argv)
 
                if (evlist__ctlfd_process(rec->evlist, &cmd) > 0) {
                        switch (cmd) {
-                       case EVLIST_CTL_CMD_ENABLE:
-                               pr_info(EVLIST_ENABLED_MSG);
-                               break;
-                       case EVLIST_CTL_CMD_DISABLE:
-                               pr_info(EVLIST_DISABLED_MSG);
-                               break;
                        case EVLIST_CTL_CMD_SNAPSHOT:
                                hit_auxtrace_snapshot_trigger(rec);
                                evlist__ctlfd_ack(rec->evlist);
                                break;
                        case EVLIST_CTL_CMD_ACK:
                        case EVLIST_CTL_CMD_UNSUPPORTED:
+                       case EVLIST_CTL_CMD_ENABLE:
+                       case EVLIST_CTL_CMD_DISABLE:
                        default:
                                break;
                        }
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 89c32692f40c..4c43c5e14fd4 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -578,14 +578,12 @@ static void process_evlist(struct evlist *evlist, 
unsigned int interval)
        if (evlist__ctlfd_process(evlist, &cmd) > 0) {
                switch (cmd) {
                case EVLIST_CTL_CMD_ENABLE:
-                       pr_info(EVLIST_ENABLED_MSG);
                        if (interval)
                                process_interval();
                        break;
                case EVLIST_CTL_CMD_DISABLE:
                        if (interval)
                                process_interval();
-                       pr_info(EVLIST_DISABLED_MSG);
                        break;
                case EVLIST_CTL_CMD_SNAPSHOT:
                case EVLIST_CTL_CMD_ACK:
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 70aff26612a9..7e0bcd1d1516 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1946,6 +1946,64 @@ int evlist__ctlfd_ack(struct evlist *evlist)
        return err;
 }
 
+static int get_cmd_arg(char *cmd_data, size_t cmd_size, char **arg)
+{
+       char *data = cmd_data + cmd_size;
+
+       /* no argument */
+       if (!*data)
+               return 0;
+
+       /* there's argument */
+       if (*data == ' ') {
+               *arg = data + 1;
+               return 1;
+       }
+
+       /* malformed */
+       return -1;
+}
+
+static int evlist__ctlfd_enable(struct evlist *evlist, char *cmd_data, bool 
enable)
+{
+       struct evsel *evsel;
+       char *name;
+       int err;
+
+       err = get_cmd_arg(cmd_data,
+                         enable ? sizeof(EVLIST_CTL_CMD_ENABLE_TAG) - 1 :
+                                  sizeof(EVLIST_CTL_CMD_DISABLE_TAG) - 1,
+                         &name);
+       if (err < 0) {
+               pr_info("failed: wrong command\n");
+               return -1;
+       }
+
+       if (err) {
+               evsel = evlist__find_evsel_by_str(evlist, name);
+               if (evsel) {
+                       if (enable)
+                               evlist__enable_evsel(evlist, name);
+                       else
+                               evlist__disable_evsel(evlist, name);
+                       pr_info("Event %s %s\n", evsel->name,
+                               enable ? "enabled" : "disabled");
+               } else {
+                       pr_info("failed: can't find '%s' event\n", name);
+               }
+       } else {
+               if (enable) {
+                       evlist__enable(evlist);
+                       pr_info(EVLIST_ENABLED_MSG);
+               } else {
+                       evlist__disable(evlist);
+                       pr_info(EVLIST_DISABLED_MSG);
+               }
+       }
+
+       return 0;
+}
+
 int evlist__ctlfd_process(struct evlist *evlist, enum evlist_ctl_cmd *cmd)
 {
        int err = 0;
@@ -1962,10 +2020,9 @@ int evlist__ctlfd_process(struct evlist *evlist, enum 
evlist_ctl_cmd *cmd)
                if (err > 0) {
                        switch (*cmd) {
                        case EVLIST_CTL_CMD_ENABLE:
-                               evlist__enable(evlist);
-                               break;
                        case EVLIST_CTL_CMD_DISABLE:
-                               evlist__disable(evlist);
+                               err = evlist__ctlfd_enable(evlist, cmd_data,
+                                                          *cmd == 
EVLIST_CTL_CMD_ENABLE);
                                break;
                        case EVLIST_CTL_CMD_SNAPSHOT:
                                break;
-- 
2.26.2

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