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Subject: [PATCH v2 02/11] perf evlist: implement control command handling
 functions
From:   Alexey Budankov <alexey.budankov@linux.intel.com>
To:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@redhat.com>
Cc:     Namhyung Kim <namhyung@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Andi Kleen <ak@linux.intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>
References: <d582cc3d-2302-c7e2-70d3-bc7ab6f628c3@linux.intel.com>
Organization: Intel Corp.
Message-ID: <142da58d-7ff1-ea73-89e0-30342a710aab@linux.intel.com>
Date:   Wed, 6 May 2020 21:19:22 +0300
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Implement functions of initialization, finalization and processing
of control commands coming from control file descriptors.

Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
---
 tools/perf/util/evlist.c | 100 +++++++++++++++++++++++++++++++++++++++
 tools/perf/util/evlist.h |  12 +++++
 2 files changed, 112 insertions(+)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 2db4bedc4f81..e086c846ef3a 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1707,3 +1707,103 @@ struct evsel *perf_evlist__reset_weak_group(struct evlist *evsel_list,
 	}
 	return leader;
 }
+
+int perf_evlist__initialize_ctlfd(struct evlist *evlist, int ctl_fd, int ctl_fd_ack)
+{
+	if (ctl_fd == -1) {
+		pr_debug("Control descriptor is not initialized\n");
+		return 0;
+	}
+
+	evlist->ctl_fd_pos = perf_evlist__add_pollfd(&evlist->core, ctl_fd, NULL, POLLIN);
+	if (evlist->ctl_fd_pos < 0) {
+		evlist->ctl_fd_pos = -1;
+		pr_err("Failed to add ctl fd entry: %m\n");
+		return -1;
+	}
+
+	evlist->ctl_fd = ctl_fd;
+	evlist->ctl_fd_ack = ctl_fd_ack;
+
+	return 0;
+}
+
+int perf_evlist__finalize_ctlfd(struct evlist *evlist)
+{
+	if (evlist->ctl_fd_pos == -1)
+		return 0;
+
+	evlist->core.pollfd.entries[evlist->ctl_fd_pos].fd = -1;
+	evlist->ctl_fd_pos = -1;
+	evlist->ctl_fd_ack = -1;
+	evlist->ctl_fd = -1;
+
+	return 0;
+}
+
+static int perf_evlist__ctlfd_recv(struct evlist *evlist, enum evlist_ctl_cmd *cmd)
+{
+	int err;
+	char buf[2];
+
+	err = read(evlist->ctl_fd, &buf, sizeof(buf));
+	if (err > 0)
+		*cmd = buf[0];
+	else if (err == -1)
+		pr_err("Failed to read from ctlfd %d: %m\n", evlist->ctl_fd);
+
+	return err;
+}
+
+static int perf_evlist__ctlfd_ack(struct evlist *evlist)
+{
+	int err;
+	char buf[2] = {CTL_CMD_ACK, '\n'};
+
+	if (evlist->ctl_fd_ack == -1)
+		return 0;
+
+	err = write(evlist->ctl_fd_ack, buf, sizeof(buf));
+	if (err == -1)
+		pr_err("failed to write to ctl_ack_fd %d: %m\n", evlist->ctl_fd_ack);
+
+	return err;
+}
+
+int perf_evlist__ctlfd_process(struct evlist *evlist, enum evlist_ctl_cmd *cmd)
+{
+	int err = 0;
+	int ctlfd_pos = evlist->ctl_fd_pos;
+	struct pollfd *entries = evlist->core.pollfd.entries;
+
+	if (!entries[ctlfd_pos].revents)
+		return 0;
+
+	if (entries[ctlfd_pos].revents & POLLIN) {
+		err = perf_evlist__ctlfd_recv(evlist, cmd);
+		if (err > 0) {
+			switch (*cmd) {
+			case CTL_CMD_ENABLE:
+				evlist__enable(evlist);
+				break;
+			case CTL_CMD_DISABLE:
+				evlist__disable(evlist);
+				break;
+			case CTL_CMD_ACK:
+			case CTL_CMD_UNSUPPORTED:
+			default:
+				pr_debug("ctlfd: unsupported %d\n", *cmd);
+				break;
+			}
+			if (!(*cmd == CTL_CMD_ACK || *cmd == CTL_CMD_UNSUPPORTED))
+				perf_evlist__ctlfd_ack(evlist);
+		}
+	}
+
+	if (entries[ctlfd_pos].revents & (POLLHUP | POLLERR))
+		perf_evlist__finalize_ctlfd(evlist);
+	else
+		entries[ctlfd_pos].revents = 0;
+
+	return err;
+}
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 62f259d89b41..84386850c290 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -358,4 +358,16 @@ void perf_evlist__force_leader(struct evlist *evlist);
 struct evsel *perf_evlist__reset_weak_group(struct evlist *evlist,
 						 struct evsel *evsel,
 						bool close);
+
+enum evlist_ctl_cmd {
+	CTL_CMD_UNSUPPORTED = 0,
+	CTL_CMD_ENABLE = 'e',
+	CTL_CMD_DISABLE = 'd',
+	CTL_CMD_ACK = 'a'
+};
+
+int perf_evlist__initialize_ctlfd(struct evlist *evlist, int ctl_fd, int ctl_fd_ack);
+int perf_evlist__finalize_ctlfd(struct evlist *evlist);
+int perf_evlist__ctlfd_process(struct evlist *evlist, enum evlist_ctl_cmd *cmd);
+
 #endif /* __PERF_EVLIST_H */
-- 
2.24.1