#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/mman.h>

#include "tests.h"
#include "util/evsel.h"
#include "util/evlist.h"
#include "util/cpumap.h"
#include "util/thread_map.h"

#define NR_LOOPS  10000000

/*
 * This test will open software clock events (cpu-clock, task-clock)
 * then check their frequency -> period conversion has no artifact of
 * setting period to 1 forcefully.
 */
static int __test__sw_clock_freq(enum perf_sw_ids clock_id)
{
	int i, err = -1;
	volatile int tmp = 0;
	u64 total_periods = 0;
	int nr_samples = 0;
	char sbuf[STRERR_BUFSIZE];
	union perf_event *event;
	struct perf_evsel *evsel;
	struct perf_evlist *evlist;
	struct perf_event_attr attr = {
		.type = PERF_TYPE_SOFTWARE,
		.config = clock_id,
		.sample_type = PERF_SAMPLE_PERIOD,
		.exclude_kernel = 1,
		.disabled = 1,
		.freq = 1,
	};
	struct cpu_map *cpus;
	struct thread_map *threads;

	attr.sample_freq = 500;

	evlist = perf_evlist__new();
	if (evlist == NULL) {
		pr_debug("perf_evlist__new\n");
		return -1;
	}

	evsel = perf_evsel__new(&attr);
	if (evsel == NULL) {
		pr_debug("perf_evsel__new\n");
		goto out_delete_evlist;
	}
	perf_evlist__add(evlist, evsel);

	cpus = cpu_map__dummy_new();
	threads = thread_map__new_by_tid(getpid());
	if (!cpus || !threads) {
		err = -ENOMEM;
		pr_debug("Not enough memory to create thread/cpu maps\n");
		goto out_free_maps;
	}

	perf_evlist__set_maps(evlist, cpus, threads);

	cpus	= NULL;
	threads = NULL;

	if (perf_evlist__open(evlist)) {
		const char *knob = "/proc/sys/kernel/perf_event_max_sample_rate";

		err = -errno;
		pr_debug("Couldn't open evlist: %s\nHint: check %s, using %" PRIu64 " in this test.\n",
			 str_error_r(errno, sbuf, sizeof(sbuf)),
			 knob, (u64)attr.sample_freq);
		goto out_delete_evlist;
	}

	err = perf_evlist__mmap(evlist, 128, true);
	if (err < 0) {
		pr_debug("failed to mmap event: %d (%s)\n", errno,
			 str_error_r(errno, sbuf, sizeof(sbuf)));
		goto out_delete_evlist;
	}

	perf_evlist__enable(evlist);

	/* collect samples */
	for (i = 0; i < NR_LOOPS; i++)
		tmp++;

	perf_evlist__disable(evlist);

	while ((event = perf_evlist__mmap_read(evlist, 0)) != NULL) {
		struct perf_sample sample;

		if (event->header.type != PERF_RECORD_SAMPLE)
			goto next_event;

		err = perf_evlist__parse_sample(evlist, event, &sample);
		if (err < 0) {
			pr_debug("Error during parse sample\n");
			goto out_delete_evlist;
		}

		total_periods += sample.period;
		nr_samples++;
next_event:
		perf_evlist__mmap_consume(evlist, 0);
	}

	if ((u64) nr_samples == total_periods) {
		pr_debug("All (%d) samples have period value of 1!\n",
			 nr_samples);
		err = -1;
	}

out_free_maps:
	cpu_map__put(cpus);
	thread_map__put(threads);
out_delete_evlist:
	perf_evlist__delete(evlist);
	return err;
}

int test__sw_clock_freq(int subtest __maybe_unused)
{
	int ret;

	ret = __test__sw_clock_freq(PERF_COUNT_SW_CPU_CLOCK);
	if (!ret)
		ret = __test__sw_clock_freq(PERF_COUNT_SW_TASK_CLOCK);

	return ret;
}
fec09e0144dc3341'>usb</a>/<a href='/cgit.cgi/linux/net-next.git/commit/drivers/usb/core?id=966d2b04e070bc040319aaebfec09e0144dc3341'>core</a>/<a href='/cgit.cgi/linux/net-next.git/commit/drivers/usb/core/notify.c?id=966d2b04e070bc040319aaebfec09e0144dc3341'>notify.c</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='966d2b04e070bc040319aaebfec09e0144dc3341'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Douglas Miller &lt;dougmill@linux.vnet.ibm.com&gt;</td><td class='right'>2017-01-28 06:42:20 -0600</td></tr>
<tr><th>committer</th><td>Tejun Heo &lt;tj@kernel.org&gt;</td><td class='right'>2017-01-28 07:49:42 -0500</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/drivers/usb/core/notify.c?id=966d2b04e070bc040319aaebfec09e0144dc3341'>966d2b04e070bc040319aaebfec09e0144dc3341</a> (<a href='/cgit.cgi/linux/net-next.git/patch/drivers/usb/core/notify.c?id=966d2b04e070bc040319aaebfec09e0144dc3341'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=966d2b04e070bc040319aaebfec09e0144dc3341'>4b96156e3d1dd4dfd6039b7c219c9dc4616da52d</a> /<a href='/cgit.cgi/linux/net-next.git/tree/drivers/usb/core/notify.c?id=966d2b04e070bc040319aaebfec09e0144dc3341'>drivers/usb/core/notify.c</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/drivers/usb/core/notify.c?id=1b1bc42c1692e9b62756323c675a44cb1a1f9dbd'>1b1bc42c1692e9b62756323c675a44cb1a1f9dbd</a> (<a href='/cgit.cgi/linux/net-next.git/diff/drivers/usb/core/notify.c?id=966d2b04e070bc040319aaebfec09e0144dc3341&amp;id2=1b1bc42c1692e9b62756323c675a44cb1a1f9dbd'>diff</a>)</td></tr></table>
<div class='commit-subject'>percpu-refcount: fix reference leak during percpu-atomic transition</div><div class='commit-msg'>percpu_ref_tryget() and percpu_ref_tryget_live() should return
"true" IFF they acquire a reference. But the return value from
atomic_long_inc_not_zero() is a long and may have high bits set,
e.g. PERCPU_COUNT_BIAS, and the return value of the tryget routines
is bool so the reference may actually be acquired but the routines
return "false" which results in a reference leak since the caller
assumes it does not need to do a corresponding percpu_ref_put().

This was seen when performing CPU hotplug during I/O, as hangs in
blk_mq_freeze_queue_wait where percpu_ref_kill (blk_mq_freeze_queue_start)
raced with percpu_ref_tryget (blk_mq_timeout_work).
Sample stack trace:

__switch_to+0x2c0/0x450
__schedule+0x2f8/0x970
schedule+0x48/0xc0
blk_mq_freeze_queue_wait+0x94/0x120
blk_mq_queue_reinit_work+0xb8/0x180
blk_mq_queue_reinit_prepare+0x84/0xa0
cpuhp_invoke_callback+0x17c/0x600
cpuhp_up_callbacks+0x58/0x150
_cpu_up+0xf0/0x1c0
do_cpu_up+0x120/0x150
cpu_subsys_online+0x64/0xe0
device_online+0xb4/0x120
online_store+0xb4/0xc0
dev_attr_store+0x68/0xa0
sysfs_kf_write+0x80/0xb0
kernfs_fop_write+0x17c/0x250
__vfs_write+0x6c/0x1e0
vfs_write+0xd0/0x270
SyS_write+0x6c/0x110
system_call+0x38/0xe0

Examination of the queue showed a single reference (no PERCPU_COUNT_BIAS,
and __PERCPU_REF_DEAD, __PERCPU_REF_ATOMIC set) and no requests.
However, conditions at the time of the race are count of PERCPU_COUNT_BIAS + 0
and __PERCPU_REF_DEAD and __PERCPU_REF_ATOMIC set.

The fix is to make the tryget routines use an actual boolean internally instead
of the atomic long result truncated to a int.

Fixes: e625305b3907 percpu-refcount: make percpu_ref based on longs instead of ints
Link: https://bugzilla.kernel.org/show_bug.cgi?id=190751
Signed-off-by: Douglas Miller &lt;dougmill@linux.vnet.ibm.com&gt;
Reviewed-by: Jens Axboe &lt;axboe@fb.com&gt;
Signed-off-by: Tejun Heo &lt;tj@kernel.org&gt;
Fixes: e625305b3907 ("percpu-refcount: make percpu_ref based on longs instead of ints")
Cc: stable@vger.kernel.org # v3.18+
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=966d2b04e070bc040319aaebfec09e0144dc3341'>Diffstat</a> (limited to 'drivers/usb/core/notify.c')</div><table summary='diffstat' class='diffstat'>