sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

4 files changed, 521 insertions, 0 deletions

diff --git a/tools/testing/selftests/rtc/.gitignore b/tools/testing/selftests/rtc/.gitignore
new file mode 100644
index 000000000..a2afe7994
--- /dev/null
+++ b/tools/testing/selftests/rtc/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+rtctest
diff --git a/tools/testing/selftests/rtc/Makefile b/tools/testing/selftests/rtc/Makefile
new file mode 100644
index 000000000..547c244a2
--- /dev/null
+++ b/tools/testing/selftests/rtc/Makefile
@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-2.0
+CFLAGS += -O3 -Wl,-no-as-needed -Wall -I$(top_srcdir)/usr/include
+LDLIBS += -lrt -lpthread -lm
+
+TEST_GEN_PROGS = rtctest
+
+TEST_FILES := settings
+
+include ../lib.mk
diff --git a/tools/testing/selftests/rtc/rtctest.c b/tools/testing/selftests/rtc/rtctest.c
new file mode 100644
index 000000000..8047d9879
--- /dev/null
+++ b/tools/testing/selftests/rtc/rtctest.c
@@ -0,0 +1,509 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Real Time Clock Driver Test Program
+ *
+ * Copyright (c) 2018 Alexandre Belloni <alexandre.belloni@bootlin.com>
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/rtc.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "kselftest_harness.h"
+
+#define NUM_UIE 3
+#define ALARM_DELTA 3
+#define READ_LOOP_DURATION_SEC 30
+#define READ_LOOP_SLEEP_MS 11
+
+static char *rtc_file = "/dev/rtc0";
+
+enum rtc_alarm_state {
+	RTC_ALARM_UNKNOWN,
+	RTC_ALARM_ENABLED,
+	RTC_ALARM_DISABLED,
+	RTC_ALARM_RES_MINUTE,
+};
+
+FIXTURE(rtc) {
+	int fd;
+};
+
+FIXTURE_SETUP(rtc) {
+	self->fd = open(rtc_file, O_RDONLY);
+}
+
+FIXTURE_TEARDOWN(rtc) {
+	close(self->fd);
+}
+
+TEST_F(rtc, date_read) {
+	int rc;
+	struct rtc_time rtc_tm;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	/* Read the RTC time/date */
+	rc = ioctl(self->fd, RTC_RD_TIME, &rtc_tm);
+	ASSERT_NE(-1, rc);
+
+	TH_LOG("Current RTC date/time is %02d/%02d/%02d %02d:%02d:%02d.",
+	       rtc_tm.tm_mday, rtc_tm.tm_mon + 1, rtc_tm.tm_year + 1900,
+	       rtc_tm.tm_hour, rtc_tm.tm_min, rtc_tm.tm_sec);
+}
+
+static time_t rtc_time_to_timestamp(struct rtc_time *rtc_time)
+{
+	struct tm tm_time = {
+	       .tm_sec = rtc_time->tm_sec,
+	       .tm_min = rtc_time->tm_min,
+	       .tm_hour = rtc_time->tm_hour,
+	       .tm_mday = rtc_time->tm_mday,
+	       .tm_mon = rtc_time->tm_mon,
+	       .tm_year = rtc_time->tm_year,
+	};
+
+	return mktime(&tm_time);
+}
+
+static void nanosleep_with_retries(long ns)
+{
+	struct timespec req = {
+		.tv_sec = 0,
+		.tv_nsec = ns,
+	};
+	struct timespec rem;
+
+	while (nanosleep(&req, &rem) != 0) {
+		req.tv_sec = rem.tv_sec;
+		req.tv_nsec = rem.tv_nsec;
+	}
+}
+
+static enum rtc_alarm_state get_rtc_alarm_state(int fd, int need_seconds)
+{
+	struct rtc_param param = { 0 };
+	int rc;
+
+	/* Validate kernel reflects unsupported RTC alarm state */
+	param.param = RTC_PARAM_FEATURES;
+	param.index = 0;
+	rc = ioctl(fd, RTC_PARAM_GET, &param);
+	if (rc < 0)
+		return RTC_ALARM_UNKNOWN;
+
+	if ((param.uvalue & _BITUL(RTC_FEATURE_ALARM)) == 0)
+		return RTC_ALARM_DISABLED;
+
+	/* Check if alarm has desired granularity */
+	if (need_seconds && (param.uvalue & _BITUL(RTC_FEATURE_ALARM_RES_MINUTE)))
+		return RTC_ALARM_RES_MINUTE;
+
+	return RTC_ALARM_ENABLED;
+}
+
+TEST_F_TIMEOUT(rtc, date_read_loop, READ_LOOP_DURATION_SEC + 2) {
+	int rc;
+	long iter_count = 0;
+	struct rtc_time rtc_tm;
+	time_t start_rtc_read, prev_rtc_read;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	TH_LOG("Continuously reading RTC time for %ds (with %dms breaks after every read).",
+	       READ_LOOP_DURATION_SEC, READ_LOOP_SLEEP_MS);
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &rtc_tm);
+	ASSERT_NE(-1, rc);
+	start_rtc_read = rtc_time_to_timestamp(&rtc_tm);
+	prev_rtc_read = start_rtc_read;
+
+	do  {
+		time_t rtc_read;
+
+		rc = ioctl(self->fd, RTC_RD_TIME, &rtc_tm);
+		ASSERT_NE(-1, rc);
+
+		rtc_read = rtc_time_to_timestamp(&rtc_tm);
+		/* Time should not go backwards */
+		ASSERT_LE(prev_rtc_read, rtc_read);
+		/* Time should not increase more then 1s at a time */
+		ASSERT_GE(prev_rtc_read + 1, rtc_read);
+
+		/* Sleep 11ms to avoid killing / overheating the RTC */
+		nanosleep_with_retries(READ_LOOP_SLEEP_MS * 1000000);
+
+		prev_rtc_read = rtc_read;
+		iter_count++;
+	} while (prev_rtc_read <= start_rtc_read + READ_LOOP_DURATION_SEC);
+
+	TH_LOG("Performed %ld RTC time reads.", iter_count);
+}
+
+TEST_F_TIMEOUT(rtc, uie_read, NUM_UIE + 2) {
+	int i, rc, irq = 0;
+	unsigned long data;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	/* Turn on update interrupts */
+	rc = ioctl(self->fd, RTC_UIE_ON, 0);
+	if (rc == -1) {
+		ASSERT_EQ(EINVAL, errno);
+		TH_LOG("skip update IRQs not supported.");
+		return;
+	}
+
+	for (i = 0; i < NUM_UIE; i++) {
+		/* This read will block */
+		rc = read(self->fd, &data, sizeof(data));
+		ASSERT_NE(-1, rc);
+		irq++;
+	}
+
+	EXPECT_EQ(NUM_UIE, irq);
+
+	rc = ioctl(self->fd, RTC_UIE_OFF, 0);
+	ASSERT_NE(-1, rc);
+}
+
+TEST_F(rtc, uie_select) {
+	int i, rc, irq = 0;
+	unsigned long data;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	/* Turn on update interrupts */
+	rc = ioctl(self->fd, RTC_UIE_ON, 0);
+	if (rc == -1) {
+		ASSERT_EQ(EINVAL, errno);
+		TH_LOG("skip update IRQs not supported.");
+		return;
+	}
+
+	for (i = 0; i < NUM_UIE; i++) {
+		struct timeval tv = { .tv_sec = 2 };
+		fd_set readfds;
+
+		FD_ZERO(&readfds);
+		FD_SET(self->fd, &readfds);
+		/* The select will wait until an RTC interrupt happens. */
+		rc = select(self->fd + 1, &readfds, NULL, NULL, &tv);
+		ASSERT_NE(-1, rc);
+		ASSERT_NE(0, rc);
+
+		/* This read won't block */
+		rc = read(self->fd, &data, sizeof(unsigned long));
+		ASSERT_NE(-1, rc);
+		irq++;
+	}
+
+	EXPECT_EQ(NUM_UIE, irq);
+
+	rc = ioctl(self->fd, RTC_UIE_OFF, 0);
+	ASSERT_NE(-1, rc);
+}
+
+TEST_F(rtc, alarm_alm_set) {
+	struct timeval tv = { .tv_sec = ALARM_DELTA + 2 };
+	unsigned long data;
+	struct rtc_time tm;
+	fd_set readfds;
+	time_t secs, new;
+	int rc;
+	enum rtc_alarm_state alarm_state = RTC_ALARM_UNKNOWN;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	alarm_state = get_rtc_alarm_state(self->fd, 1);
+	if (alarm_state == RTC_ALARM_DISABLED)
+		SKIP(return, "Skipping test since alarms are not supported.");
+	if (alarm_state == RTC_ALARM_RES_MINUTE)
+		SKIP(return, "Skipping test since alarms has only minute granularity.");
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &tm);
+	ASSERT_NE(-1, rc);
+
+	secs = timegm((struct tm *)&tm) + ALARM_DELTA;
+	gmtime_r(&secs, (struct tm *)&tm);
+
+	rc = ioctl(self->fd, RTC_ALM_SET, &tm);
+	if (rc == -1) {
+		/*
+		 * Report error if rtc alarm was enabled. Fallback to check ioctl
+		 * error number if rtc alarm state is unknown.
+		 */
+		ASSERT_EQ(RTC_ALARM_UNKNOWN, alarm_state);
+		ASSERT_EQ(EINVAL, errno);
+		TH_LOG("skip alarms are not supported.");
+		return;
+	}
+
+	rc = ioctl(self->fd, RTC_ALM_READ, &tm);
+	ASSERT_NE(-1, rc);
+
+	TH_LOG("Alarm time now set to %02d:%02d:%02d.",
+	       tm.tm_hour, tm.tm_min, tm.tm_sec);
+
+	/* Enable alarm interrupts */
+	rc = ioctl(self->fd, RTC_AIE_ON, 0);
+	ASSERT_NE(-1, rc);
+
+	FD_ZERO(&readfds);
+	FD_SET(self->fd, &readfds);
+
+	rc = select(self->fd + 1, &readfds, NULL, NULL, &tv);
+	ASSERT_NE(-1, rc);
+	ASSERT_NE(0, rc);
+
+	/* Disable alarm interrupts */
+	rc = ioctl(self->fd, RTC_AIE_OFF, 0);
+	ASSERT_NE(-1, rc);
+
+	rc = read(self->fd, &data, sizeof(unsigned long));
+	ASSERT_NE(-1, rc);
+	TH_LOG("data: %lx", data);
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &tm);
+	ASSERT_NE(-1, rc);
+
+	new = timegm((struct tm *)&tm);
+	ASSERT_EQ(new, secs);
+}
+
+TEST_F(rtc, alarm_wkalm_set) {
+	struct timeval tv = { .tv_sec = ALARM_DELTA + 2 };
+	struct rtc_wkalrm alarm = { 0 };
+	struct rtc_time tm;
+	unsigned long data;
+	fd_set readfds;
+	time_t secs, new;
+	int rc;
+	enum rtc_alarm_state alarm_state = RTC_ALARM_UNKNOWN;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	alarm_state = get_rtc_alarm_state(self->fd, 1);
+	if (alarm_state == RTC_ALARM_DISABLED)
+		SKIP(return, "Skipping test since alarms are not supported.");
+	if (alarm_state == RTC_ALARM_RES_MINUTE)
+		SKIP(return, "Skipping test since alarms has only minute granularity.");
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &alarm.time);
+	ASSERT_NE(-1, rc);
+
+	secs = timegm((struct tm *)&alarm.time) + ALARM_DELTA;
+	gmtime_r(&secs, (struct tm *)&alarm.time);
+
+	alarm.enabled = 1;
+
+	rc = ioctl(self->fd, RTC_WKALM_SET, &alarm);
+	if (rc == -1) {
+		/*
+		 * Report error if rtc alarm was enabled. Fallback to check ioctl
+		 * error number if rtc alarm state is unknown.
+		 */
+		ASSERT_EQ(RTC_ALARM_UNKNOWN, alarm_state);
+		ASSERT_EQ(EINVAL, errno);
+		TH_LOG("skip alarms are not supported.");
+		return;
+	}
+
+	rc = ioctl(self->fd, RTC_WKALM_RD, &alarm);
+	ASSERT_NE(-1, rc);
+
+	TH_LOG("Alarm time now set to %02d/%02d/%02d %02d:%02d:%02d.",
+	       alarm.time.tm_mday, alarm.time.tm_mon + 1,
+	       alarm.time.tm_year + 1900, alarm.time.tm_hour,
+	       alarm.time.tm_min, alarm.time.tm_sec);
+
+	FD_ZERO(&readfds);
+	FD_SET(self->fd, &readfds);
+
+	rc = select(self->fd + 1, &readfds, NULL, NULL, &tv);
+	ASSERT_NE(-1, rc);
+	ASSERT_NE(0, rc);
+
+	rc = read(self->fd, &data, sizeof(unsigned long));
+	ASSERT_NE(-1, rc);
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &tm);
+	ASSERT_NE(-1, rc);
+
+	new = timegm((struct tm *)&tm);
+	ASSERT_EQ(new, secs);
+}
+
+TEST_F_TIMEOUT(rtc, alarm_alm_set_minute, 65) {
+	struct timeval tv = { .tv_sec = 62 };
+	unsigned long data;
+	struct rtc_time tm;
+	fd_set readfds;
+	time_t secs, new;
+	int rc;
+	enum rtc_alarm_state alarm_state = RTC_ALARM_UNKNOWN;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	alarm_state = get_rtc_alarm_state(self->fd, 0);
+	if (alarm_state == RTC_ALARM_DISABLED)
+		SKIP(return, "Skipping test since alarms are not supported.");
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &tm);
+	ASSERT_NE(-1, rc);
+
+	secs = timegm((struct tm *)&tm) + 60 - tm.tm_sec;
+	gmtime_r(&secs, (struct tm *)&tm);
+
+	rc = ioctl(self->fd, RTC_ALM_SET, &tm);
+	if (rc == -1) {
+		/*
+		 * Report error if rtc alarm was enabled. Fallback to check ioctl
+		 * error number if rtc alarm state is unknown.
+		 */
+		ASSERT_EQ(RTC_ALARM_UNKNOWN, alarm_state);
+		ASSERT_EQ(EINVAL, errno);
+		TH_LOG("skip alarms are not supported.");
+		return;
+	}
+
+	rc = ioctl(self->fd, RTC_ALM_READ, &tm);
+	ASSERT_NE(-1, rc);
+
+	TH_LOG("Alarm time now set to %02d:%02d:%02d.",
+	       tm.tm_hour, tm.tm_min, tm.tm_sec);
+
+	/* Enable alarm interrupts */
+	rc = ioctl(self->fd, RTC_AIE_ON, 0);
+	ASSERT_NE(-1, rc);
+
+	FD_ZERO(&readfds);
+	FD_SET(self->fd, &readfds);
+
+	rc = select(self->fd + 1, &readfds, NULL, NULL, &tv);
+	ASSERT_NE(-1, rc);
+	ASSERT_NE(0, rc);
+
+	/* Disable alarm interrupts */
+	rc = ioctl(self->fd, RTC_AIE_OFF, 0);
+	ASSERT_NE(-1, rc);
+
+	rc = read(self->fd, &data, sizeof(unsigned long));
+	ASSERT_NE(-1, rc);
+	TH_LOG("data: %lx", data);
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &tm);
+	ASSERT_NE(-1, rc);
+
+	new = timegm((struct tm *)&tm);
+	ASSERT_EQ(new, secs);
+}
+
+TEST_F_TIMEOUT(rtc, alarm_wkalm_set_minute, 65) {
+	struct timeval tv = { .tv_sec = 62 };
+	struct rtc_wkalrm alarm = { 0 };
+	struct rtc_time tm;
+	unsigned long data;
+	fd_set readfds;
+	time_t secs, new;
+	int rc;
+	enum rtc_alarm_state alarm_state = RTC_ALARM_UNKNOWN;
+
+	if (self->fd == -1 && errno == ENOENT)
+		SKIP(return, "Skipping test since %s does not exist", rtc_file);
+	ASSERT_NE(-1, self->fd);
+
+	alarm_state = get_rtc_alarm_state(self->fd, 0);
+	if (alarm_state == RTC_ALARM_DISABLED)
+		SKIP(return, "Skipping test since alarms are not supported.");
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &alarm.time);
+	ASSERT_NE(-1, rc);
+
+	secs = timegm((struct tm *)&alarm.time) + 60 - alarm.time.tm_sec;
+	gmtime_r(&secs, (struct tm *)&alarm.time);
+
+	alarm.enabled = 1;
+
+	rc = ioctl(self->fd, RTC_WKALM_SET, &alarm);
+	if (rc == -1) {
+		/*
+		 * Report error if rtc alarm was enabled. Fallback to check ioctl
+		 * error number if rtc alarm state is unknown.
+		 */
+		ASSERT_EQ(RTC_ALARM_UNKNOWN, alarm_state);
+		ASSERT_EQ(EINVAL, errno);
+		TH_LOG("skip alarms are not supported.");
+		return;
+	}
+
+	rc = ioctl(self->fd, RTC_WKALM_RD, &alarm);
+	ASSERT_NE(-1, rc);
+
+	TH_LOG("Alarm time now set to %02d/%02d/%02d %02d:%02d:%02d.",
+	       alarm.time.tm_mday, alarm.time.tm_mon + 1,
+	       alarm.time.tm_year + 1900, alarm.time.tm_hour,
+	       alarm.time.tm_min, alarm.time.tm_sec);
+
+	FD_ZERO(&readfds);
+	FD_SET(self->fd, &readfds);
+
+	rc = select(self->fd + 1, &readfds, NULL, NULL, &tv);
+	ASSERT_NE(-1, rc);
+	ASSERT_NE(0, rc);
+
+	rc = read(self->fd, &data, sizeof(unsigned long));
+	ASSERT_NE(-1, rc);
+
+	rc = ioctl(self->fd, RTC_RD_TIME, &tm);
+	ASSERT_NE(-1, rc);
+
+	new = timegm((struct tm *)&tm);
+	ASSERT_EQ(new, secs);
+}
+
+int main(int argc, char **argv)
+{
+	int ret = -1;
+
+	switch (argc) {
+	case 2:
+		rtc_file = argv[1];
+		/* FALLTHROUGH */
+	case 1:
+		break;
+	default:
+		fprintf(stderr, "usage: %s [rtcdev]\n", argv[0]);
+		return 1;
+	}
+
+	/* Run the test if rtc_file is accessible */
+	if (access(rtc_file, R_OK) == 0)
+		ret = test_harness_run(argc, argv);
+	else
+		ksft_exit_skip("[SKIP]: Cannot access rtc file %s - Exiting\n",
+						rtc_file);
+
+	return ret;
+}
diff --git a/tools/testing/selftests/rtc/settings b/tools/testing/selftests/rtc/settings
new file mode 100644
index 000000000..0c1a2075d
--- /dev/null
+++ b/tools/testing/selftests/rtc/settings
@@ -0,0 +1 @@
+timeout=210