/*
 * call-path.h: Manipulate a tree data structure containing function call paths
 * Copyright (c) 2014, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 */

#ifndef __PERF_CALL_PATH_H
#define __PERF_CALL_PATH_H

#include <sys/types.h>

#include <linux/types.h>
#include <linux/rbtree.h>

/**
 * struct call_path - node in list of calls leading to a function call.
 * @parent: call path to the parent function call
 * @sym: symbol of function called
 * @ip: only if sym is null, the ip of the function
 * @db_id: id used for db-export
 * @in_kernel: whether function is a in the kernel
 * @rb_node: node in parent's tree of called functions
 * @children: tree of call paths of functions called
 *
 * In combination with the call_return structure, the call_path structure
 * defines a context-sensitve call-graph.
 */
struct call_path {
	struct call_path *parent;
	struct symbol *sym;
	u64 ip;
	u64 db_id;
	bool in_kernel;
	struct rb_node rb_node;
	struct rb_root children;
};

#define CALL_PATH_BLOCK_SHIFT 8
#define CALL_PATH_BLOCK_SIZE (1 << CALL_PATH_BLOCK_SHIFT)
#define CALL_PATH_BLOCK_MASK (CALL_PATH_BLOCK_SIZE - 1)

struct call_path_block {
	struct call_path cp[CALL_PATH_BLOCK_SIZE];
	struct list_head node;
};

/**
 * struct call_path_root - root of all call paths.
 * @call_path: root call path
 * @blocks: list of blocks to store call paths
 * @next: next free space
 * @sz: number of spaces
 */
struct call_path_root {
	struct call_path call_path;
	struct list_head blocks;
	size_t next;
	size_t sz;
};

struct call_path_root *call_path_root__new(void);
void call_path_root__free(struct call_path_root *cpr);

struct call_path *call_path__findnew(struct call_path_root *cpr,
				     struct call_path *parent,
				     struct symbol *sym, u64 ip, u64 ks);

#endif
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<div class='path'>path: <a href='/cgit.cgi/linux/net-next.git/log/?id=74470954857c264168d2b5a113904cf0cfd27d18&amp;showmsg=1'>root</a>/<a href='/cgit.cgi/linux/net-next.git/log/net?id=74470954857c264168d2b5a113904cf0cfd27d18&amp;showmsg=1'>net</a>/<a href='/cgit.cgi/linux/net-next.git/log/net/netrom?id=74470954857c264168d2b5a113904cf0cfd27d18&amp;showmsg=1'>netrom</a>/<a href='/cgit.cgi/linux/net-next.git/log/net/netrom/sysctl_net_netrom.c?id=74470954857c264168d2b5a113904cf0cfd27d18&amp;showmsg=1'>sysctl_net_netrom.c</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/cgit.cgi/linux/net-next.git/log/net/netrom/sysctl_net_netrom.c?id=74470954857c264168d2b5a113904cf0cfd27d18'>Collapse</a>)</th><th class='left'>Author</th><th class='left'>Files</th><th class='left'>Lines</th></tr>
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<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/sound/pci/hda/patch_ca0132.c?id=966d2b04e070bc040319aaebfec09e0144dc3341'>966d2b04e070bc040319aaebfec09e0144dc3341</a> (<a href='/cgit.cgi/linux/net-next.git/patch/sound/pci/hda/patch_ca0132.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/sound/pci/hda/patch_ca0132.c?id=966d2b04e070bc040319aaebfec09e0144dc3341'>sound/pci/hda/patch_ca0132.c</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/sound/pci/hda/patch_ca0132.c?id=1b1bc42c1692e9b62756323c675a44cb1a1f9dbd'>1b1bc42c1692e9b62756323c675a44cb1a1f9dbd</a> (<a href='/cgit.cgi/linux/net-next.git/diff/sound/pci/hda/patch_ca0132.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 'sound/pci/hda/patch_ca0132.c')</div><table summary='diffstat' class='diffstat'>