/usr/src/lttng-modules-2.7.1/lttng-tracker-pid.c is in lttng-modules-dkms 2.7.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 | /*
* lttng-tracker-pid.c
*
* LTTng Process ID trackering.
*
* Copyright (C) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; only
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/seq_file.h>
#include <linux/stringify.h>
#include <linux/hash.h>
#include <linux/rcupdate.h>
#include "wrapper/tracepoint.h"
#include "wrapper/rcu.h"
#include "wrapper/list.h"
#include "lttng-events.h"
/*
* Hash table is allocated and freed when there are no possible
* concurrent lookups (ensured by the alloc/free caller). However,
* there can be concurrent RCU lookups vs add/del operations.
*
* Concurrent updates of the PID hash table are forbidden: the caller
* must ensure mutual exclusion. This is currently done by holding the
* sessions_mutex across calls to create, destroy, add, and del
* functions of this API.
*/
int lttng_pid_tracker_get_node_pid(const struct lttng_pid_hash_node *node)
{
return node->pid;
}
/*
* Lookup performed from RCU read-side critical section (RCU sched),
* protected by preemption off at the tracepoint call site.
* Return 1 if found, 0 if not found.
*/
bool lttng_pid_tracker_lookup(struct lttng_pid_tracker *lpf, int pid)
{
struct hlist_head *head;
struct lttng_pid_hash_node *e;
uint32_t hash = hash_32(pid, 32);
head = &lpf->pid_hash[hash & (LTTNG_PID_TABLE_SIZE - 1)];
lttng_hlist_for_each_entry_rcu(e, head, hlist) {
if (pid == e->pid)
return 1; /* Found */
}
return 0;
}
EXPORT_SYMBOL_GPL(lttng_pid_tracker_lookup);
/*
* Tracker add and del operations support concurrent RCU lookups.
*/
int lttng_pid_tracker_add(struct lttng_pid_tracker *lpf, int pid)
{
struct hlist_head *head;
struct lttng_pid_hash_node *e;
uint32_t hash = hash_32(pid, 32);
head = &lpf->pid_hash[hash & (LTTNG_PID_TABLE_SIZE - 1)];
lttng_hlist_for_each_entry(e, head, hlist) {
if (pid == e->pid)
return -EEXIST;
}
e = kmalloc(sizeof(struct lttng_pid_hash_node), GFP_KERNEL);
if (!e)
return -ENOMEM;
e->pid = pid;
hlist_add_head_rcu(&e->hlist, head);
return 0;
}
static
void pid_tracker_del_node_rcu(struct lttng_pid_hash_node *e)
{
hlist_del_rcu(&e->hlist);
/*
* We choose to use a heavyweight synchronize on removal here,
* since removal of a PID from the tracker mask is a rare
* operation, and we don't want to use more cache lines than
* what we really need when doing the PID lookups, so we don't
* want to afford adding a rcu_head field to those pid hash
* node.
*/
synchronize_trace();
kfree(e);
}
/*
* This removal is only used on destroy, so it does not need to support
* concurrent RCU lookups.
*/
static
void pid_tracker_del_node(struct lttng_pid_hash_node *e)
{
hlist_del(&e->hlist);
kfree(e);
}
int lttng_pid_tracker_del(struct lttng_pid_tracker *lpf, int pid)
{
struct hlist_head *head;
struct lttng_pid_hash_node *e;
uint32_t hash = hash_32(pid, 32);
head = &lpf->pid_hash[hash & (LTTNG_PID_TABLE_SIZE - 1)];
/*
* No need of _safe iteration, because we stop traversal as soon
* as we remove the entry.
*/
lttng_hlist_for_each_entry(e, head, hlist) {
if (pid == e->pid) {
pid_tracker_del_node_rcu(e);
return 0;
}
}
return -ENOENT; /* Not found */
}
struct lttng_pid_tracker *lttng_pid_tracker_create(void)
{
return kzalloc(sizeof(struct lttng_pid_tracker), GFP_KERNEL);
}
void lttng_pid_tracker_destroy(struct lttng_pid_tracker *lpf)
{
int i;
for (i = 0; i < LTTNG_PID_TABLE_SIZE; i++) {
struct hlist_head *head = &lpf->pid_hash[i];
struct lttng_pid_hash_node *e;
struct hlist_node *tmp;
lttng_hlist_for_each_entry_safe(e, tmp, head, hlist)
pid_tracker_del_node(e);
}
kfree(lpf);
}
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