/*
 * Copyright 2013, Michael Ellerman, IBM Corp.
 * Licensed under GPLv2.
 */

#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
#include <string.h>
#include <stdio.h>
#include <sys/ioctl.h>

#include "event.h"


int perf_event_open(struct perf_event_attr *attr, pid_t pid, int cpu,
		int group_fd, unsigned long flags)
{
	return syscall(__NR_perf_event_open, attr, pid, cpu,
			   group_fd, flags);
}

void event_init_opts(struct event *e, u64 config, int type, char *name)
{
	memset(e, 0, sizeof(*e));

	e->name = name;

	e->attr.type = type;
	e->attr.config = config;
	e->attr.size = sizeof(e->attr);
	/* This has to match the structure layout in the header */
	e->attr.read_format = PERF_FORMAT_TOTAL_TIME_ENABLED | \
				  PERF_FORMAT_TOTAL_TIME_RUNNING;
}

void event_init_named(struct event *e, u64 config, char *name)
{
	event_init_opts(e, config, PERF_TYPE_RAW, name);
}

void event_init(struct event *e, u64 config)
{
	event_init_opts(e, config, PERF_TYPE_RAW, "event");
}

#define PERF_CURRENT_PID	0
#define PERF_NO_PID		-1
#define PERF_NO_CPU		-1
#define PERF_NO_GROUP		-1

int event_open_with_options(struct event *e, pid_t pid, int cpu, int group_fd)
{
	e->fd = perf_event_open(&e->attr, pid, cpu, group_fd, 0);
	if (e->fd == -1) {
		perror("perf_event_open");
		return -1;
	}

	return 0;
}

int event_open_with_group(struct event *e, int group_fd)
{
	return event_open_with_options(e, PERF_CURRENT_PID, PERF_NO_CPU, group_fd);
}

int event_open_with_pid(struct event *e, pid_t pid)
{
	return event_open_with_options(e, pid, PERF_NO_CPU, PERF_NO_GROUP);
}

int event_open_with_cpu(struct event *e, int cpu)
{
	return event_open_with_options(e, PERF_NO_PID, cpu, PERF_NO_GROUP);
}

int event_open(struct event *e)
{
	return event_open_with_options(e, PERF_CURRENT_PID, PERF_NO_CPU, PERF_NO_GROUP);
}

void event_close(struct event *e)
{
	close(e->fd);
}

int event_enable(struct event *e)
{
	return ioctl(e->fd, PERF_EVENT_IOC_ENABLE);
}

int event_disable(struct event *e)
{
	return ioctl(e->fd, PERF_EVENT_IOC_DISABLE);
}

int event_reset(struct event *e)
{
	return ioctl(e->fd, PERF_EVENT_IOC_RESET);
}

int event_read(struct event *e)
{
	int rc;

	rc = read(e->fd, &e->result, sizeof(e->result));
	if (rc != sizeof(e->result)) {
		fprintf(stderr, "read error on event %p!\n", e);
		return -1;
	}

	return 0;
}

void event_report_justified(struct event *e, int name_width, int result_width)
{
	printf("%*s: result %*llu ", name_width, e->name, result_width,
	       e->result.value);

	if (e->result.running == e->result.enabled)
		printf("running/enabled %llu\n", e->result.running);
	else
		printf("running %llu enabled %llu\n", e->result.running,
			e->result.enabled);
}

void event_report(struct event *e)
{
	event_report_justified(e, 0, 0);
}
linux/net-next.git/commit/fs?id=966d2b04e070bc040319aaebfec09e0144dc3341'>fs</a>/<a href='/cgit.cgi/linux/net-next.git/commit/fs/xfs?id=966d2b04e070bc040319aaebfec09e0144dc3341'>xfs</a>/<a href='/cgit.cgi/linux/net-next.git/commit/fs/xfs/xfs_qm_bhv.c?id=966d2b04e070bc040319aaebfec09e0144dc3341'>xfs_qm_bhv.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/fs/xfs/xfs_qm_bhv.c?id=966d2b04e070bc040319aaebfec09e0144dc3341'>966d2b04e070bc040319aaebfec09e0144dc3341</a> (<a href='/cgit.cgi/linux/net-next.git/patch/fs/xfs/xfs_qm_bhv.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/fs/xfs/xfs_qm_bhv.c?id=966d2b04e070bc040319aaebfec09e0144dc3341'>fs/xfs/xfs_qm_bhv.c</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/fs/xfs/xfs_qm_bhv.c?id=1b1bc42c1692e9b62756323c675a44cb1a1f9dbd'>1b1bc42c1692e9b62756323c675a44cb1a1f9dbd</a> (<a href='/cgit.cgi/linux/net-next.git/diff/fs/xfs/xfs_qm_bhv.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 'fs/xfs/xfs_qm_bhv.c')</div><table summary='diffstat' class='diffstat'>