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d430d3d7e6
Introduce: static __always_inline bool static_branch(struct jump_label_key *key); instead of the old JUMP_LABEL(key, label) macro. In this way, jump labels become really easy to use: Define: struct jump_label_key jump_key; Can be used as: if (static_branch(&jump_key)) do unlikely code enable/disale via: jump_label_inc(&jump_key); jump_label_dec(&jump_key); that's it! For the jump labels disabled case, the static_branch() becomes an atomic_read(), and jump_label_inc()/dec() are simply atomic_inc(), atomic_dec() operations. We show testing results for this change below. Thanks to H. Peter Anvin for suggesting the 'static_branch()' construct. Since we now require a 'struct jump_label_key *key', we can store a pointer into the jump table addresses. In this way, we can enable/disable jump labels, in basically constant time. This change allows us to completely remove the previous hashtable scheme. Thanks to Peter Zijlstra for this re-write. Testing: I ran a series of 'tbench 20' runs 5 times (with reboots) for 3 configurations, where tracepoints were disabled. jump label configured in avg: 815.6 jump label *not* configured in (using atomic reads) avg: 800.1 jump label *not* configured in (regular reads) avg: 803.4 Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20110316212947.GA8792@redhat.com> Signed-off-by: Jason Baron <jbaron@redhat.com> Suggested-by: H. Peter Anvin <hpa@linux.intel.com> Tested-by: David Daney <ddaney@caviumnetworks.com> Acked-by: Ralf Baechle <ralf@linux-mips.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
641 lines
16 KiB
C
641 lines
16 KiB
C
/*
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* Copyright (C) 2008 Mathieu Desnoyers
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#include <linux/module.h>
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#include <linux/mutex.h>
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#include <linux/types.h>
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#include <linux/jhash.h>
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#include <linux/list.h>
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#include <linux/rcupdate.h>
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#include <linux/tracepoint.h>
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#include <linux/err.h>
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include <linux/jump_label.h>
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extern struct tracepoint * const __start___tracepoints_ptrs[];
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extern struct tracepoint * const __stop___tracepoints_ptrs[];
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/* Set to 1 to enable tracepoint debug output */
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static const int tracepoint_debug;
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/*
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* tracepoints_mutex nests inside module_mutex. Tracepoints mutex protects the
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* builtin and module tracepoints and the hash table.
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*/
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static DEFINE_MUTEX(tracepoints_mutex);
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/*
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* Tracepoint hash table, containing the active tracepoints.
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* Protected by tracepoints_mutex.
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*/
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#define TRACEPOINT_HASH_BITS 6
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#define TRACEPOINT_TABLE_SIZE (1 << TRACEPOINT_HASH_BITS)
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static struct hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
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/*
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* Note about RCU :
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* It is used to delay the free of multiple probes array until a quiescent
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* state is reached.
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* Tracepoint entries modifications are protected by the tracepoints_mutex.
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*/
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struct tracepoint_entry {
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struct hlist_node hlist;
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struct tracepoint_func *funcs;
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int refcount; /* Number of times armed. 0 if disarmed. */
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char name[0];
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};
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struct tp_probes {
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union {
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struct rcu_head rcu;
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struct list_head list;
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} u;
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struct tracepoint_func probes[0];
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};
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static inline void *allocate_probes(int count)
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{
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struct tp_probes *p = kmalloc(count * sizeof(struct tracepoint_func)
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+ sizeof(struct tp_probes), GFP_KERNEL);
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return p == NULL ? NULL : p->probes;
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}
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static void rcu_free_old_probes(struct rcu_head *head)
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{
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kfree(container_of(head, struct tp_probes, u.rcu));
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}
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static inline void release_probes(struct tracepoint_func *old)
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{
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if (old) {
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struct tp_probes *tp_probes = container_of(old,
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struct tp_probes, probes[0]);
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call_rcu_sched(&tp_probes->u.rcu, rcu_free_old_probes);
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}
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}
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static void debug_print_probes(struct tracepoint_entry *entry)
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{
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int i;
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if (!tracepoint_debug || !entry->funcs)
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return;
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for (i = 0; entry->funcs[i].func; i++)
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printk(KERN_DEBUG "Probe %d : %p\n", i, entry->funcs[i].func);
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}
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static struct tracepoint_func *
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tracepoint_entry_add_probe(struct tracepoint_entry *entry,
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void *probe, void *data)
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{
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int nr_probes = 0;
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struct tracepoint_func *old, *new;
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WARN_ON(!probe);
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debug_print_probes(entry);
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old = entry->funcs;
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if (old) {
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/* (N -> N+1), (N != 0, 1) probes */
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for (nr_probes = 0; old[nr_probes].func; nr_probes++)
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if (old[nr_probes].func == probe &&
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old[nr_probes].data == data)
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return ERR_PTR(-EEXIST);
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}
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/* + 2 : one for new probe, one for NULL func */
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new = allocate_probes(nr_probes + 2);
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if (new == NULL)
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return ERR_PTR(-ENOMEM);
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if (old)
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memcpy(new, old, nr_probes * sizeof(struct tracepoint_func));
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new[nr_probes].func = probe;
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new[nr_probes].data = data;
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new[nr_probes + 1].func = NULL;
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entry->refcount = nr_probes + 1;
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entry->funcs = new;
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debug_print_probes(entry);
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return old;
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}
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static void *
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tracepoint_entry_remove_probe(struct tracepoint_entry *entry,
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void *probe, void *data)
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{
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int nr_probes = 0, nr_del = 0, i;
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struct tracepoint_func *old, *new;
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old = entry->funcs;
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if (!old)
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return ERR_PTR(-ENOENT);
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debug_print_probes(entry);
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/* (N -> M), (N > 1, M >= 0) probes */
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for (nr_probes = 0; old[nr_probes].func; nr_probes++) {
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if (!probe ||
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(old[nr_probes].func == probe &&
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old[nr_probes].data == data))
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nr_del++;
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}
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if (nr_probes - nr_del == 0) {
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/* N -> 0, (N > 1) */
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entry->funcs = NULL;
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entry->refcount = 0;
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debug_print_probes(entry);
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return old;
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} else {
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int j = 0;
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/* N -> M, (N > 1, M > 0) */
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/* + 1 for NULL */
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new = allocate_probes(nr_probes - nr_del + 1);
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if (new == NULL)
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return ERR_PTR(-ENOMEM);
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for (i = 0; old[i].func; i++)
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if (probe &&
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(old[i].func != probe || old[i].data != data))
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new[j++] = old[i];
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new[nr_probes - nr_del].func = NULL;
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entry->refcount = nr_probes - nr_del;
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entry->funcs = new;
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}
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debug_print_probes(entry);
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return old;
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}
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/*
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* Get tracepoint if the tracepoint is present in the tracepoint hash table.
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* Must be called with tracepoints_mutex held.
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* Returns NULL if not present.
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*/
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static struct tracepoint_entry *get_tracepoint(const char *name)
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{
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struct hlist_head *head;
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struct hlist_node *node;
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struct tracepoint_entry *e;
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u32 hash = jhash(name, strlen(name), 0);
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head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
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hlist_for_each_entry(e, node, head, hlist) {
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if (!strcmp(name, e->name))
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return e;
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}
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return NULL;
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}
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/*
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* Add the tracepoint to the tracepoint hash table. Must be called with
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* tracepoints_mutex held.
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*/
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static struct tracepoint_entry *add_tracepoint(const char *name)
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{
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struct hlist_head *head;
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struct hlist_node *node;
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struct tracepoint_entry *e;
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size_t name_len = strlen(name) + 1;
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u32 hash = jhash(name, name_len-1, 0);
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head = &tracepoint_table[hash & (TRACEPOINT_TABLE_SIZE - 1)];
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hlist_for_each_entry(e, node, head, hlist) {
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if (!strcmp(name, e->name)) {
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printk(KERN_NOTICE
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"tracepoint %s busy\n", name);
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return ERR_PTR(-EEXIST); /* Already there */
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}
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}
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/*
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* Using kmalloc here to allocate a variable length element. Could
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* cause some memory fragmentation if overused.
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*/
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e = kmalloc(sizeof(struct tracepoint_entry) + name_len, GFP_KERNEL);
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if (!e)
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return ERR_PTR(-ENOMEM);
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memcpy(&e->name[0], name, name_len);
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e->funcs = NULL;
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e->refcount = 0;
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hlist_add_head(&e->hlist, head);
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return e;
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}
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/*
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* Remove the tracepoint from the tracepoint hash table. Must be called with
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* mutex_lock held.
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*/
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static inline void remove_tracepoint(struct tracepoint_entry *e)
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{
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hlist_del(&e->hlist);
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kfree(e);
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}
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/*
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* Sets the probe callback corresponding to one tracepoint.
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*/
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static void set_tracepoint(struct tracepoint_entry **entry,
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struct tracepoint *elem, int active)
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{
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WARN_ON(strcmp((*entry)->name, elem->name) != 0);
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if (elem->regfunc && !jump_label_enabled(&elem->key) && active)
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elem->regfunc();
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else if (elem->unregfunc && jump_label_enabled(&elem->key) && !active)
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elem->unregfunc();
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/*
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* rcu_assign_pointer has a smp_wmb() which makes sure that the new
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* probe callbacks array is consistent before setting a pointer to it.
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* This array is referenced by __DO_TRACE from
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* include/linux/tracepoints.h. A matching smp_read_barrier_depends()
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* is used.
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*/
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rcu_assign_pointer(elem->funcs, (*entry)->funcs);
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if (active && !jump_label_enabled(&elem->key))
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jump_label_inc(&elem->key);
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else if (!active && jump_label_enabled(&elem->key))
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jump_label_dec(&elem->key);
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}
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/*
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* Disable a tracepoint and its probe callback.
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* Note: only waiting an RCU period after setting elem->call to the empty
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* function insures that the original callback is not used anymore. This insured
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* by preempt_disable around the call site.
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*/
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static void disable_tracepoint(struct tracepoint *elem)
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{
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if (elem->unregfunc && jump_label_enabled(&elem->key))
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elem->unregfunc();
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if (jump_label_enabled(&elem->key))
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jump_label_dec(&elem->key);
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rcu_assign_pointer(elem->funcs, NULL);
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}
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/**
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* tracepoint_update_probe_range - Update a probe range
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* @begin: beginning of the range
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* @end: end of the range
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*
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* Updates the probe callback corresponding to a range of tracepoints.
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*/
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void tracepoint_update_probe_range(struct tracepoint * const *begin,
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struct tracepoint * const *end)
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{
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struct tracepoint * const *iter;
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struct tracepoint_entry *mark_entry;
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if (!begin)
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return;
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mutex_lock(&tracepoints_mutex);
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for (iter = begin; iter < end; iter++) {
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mark_entry = get_tracepoint((*iter)->name);
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if (mark_entry) {
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set_tracepoint(&mark_entry, *iter,
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!!mark_entry->refcount);
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} else {
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disable_tracepoint(*iter);
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}
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}
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mutex_unlock(&tracepoints_mutex);
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}
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/*
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* Update probes, removing the faulty probes.
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*/
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static void tracepoint_update_probes(void)
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{
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/* Core kernel tracepoints */
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tracepoint_update_probe_range(__start___tracepoints_ptrs,
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__stop___tracepoints_ptrs);
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/* tracepoints in modules. */
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module_update_tracepoints();
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}
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static struct tracepoint_func *
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tracepoint_add_probe(const char *name, void *probe, void *data)
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{
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struct tracepoint_entry *entry;
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struct tracepoint_func *old;
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entry = get_tracepoint(name);
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if (!entry) {
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entry = add_tracepoint(name);
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if (IS_ERR(entry))
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return (struct tracepoint_func *)entry;
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}
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old = tracepoint_entry_add_probe(entry, probe, data);
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if (IS_ERR(old) && !entry->refcount)
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remove_tracepoint(entry);
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return old;
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}
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/**
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* tracepoint_probe_register - Connect a probe to a tracepoint
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* @name: tracepoint name
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* @probe: probe handler
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*
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* Returns 0 if ok, error value on error.
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* The probe address must at least be aligned on the architecture pointer size.
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*/
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int tracepoint_probe_register(const char *name, void *probe, void *data)
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{
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struct tracepoint_func *old;
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mutex_lock(&tracepoints_mutex);
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old = tracepoint_add_probe(name, probe, data);
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mutex_unlock(&tracepoints_mutex);
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if (IS_ERR(old))
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return PTR_ERR(old);
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tracepoint_update_probes(); /* may update entry */
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release_probes(old);
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return 0;
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}
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EXPORT_SYMBOL_GPL(tracepoint_probe_register);
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static struct tracepoint_func *
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tracepoint_remove_probe(const char *name, void *probe, void *data)
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{
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struct tracepoint_entry *entry;
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struct tracepoint_func *old;
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entry = get_tracepoint(name);
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if (!entry)
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return ERR_PTR(-ENOENT);
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old = tracepoint_entry_remove_probe(entry, probe, data);
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if (IS_ERR(old))
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return old;
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if (!entry->refcount)
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remove_tracepoint(entry);
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return old;
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}
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/**
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* tracepoint_probe_unregister - Disconnect a probe from a tracepoint
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* @name: tracepoint name
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* @probe: probe function pointer
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*
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* We do not need to call a synchronize_sched to make sure the probes have
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* finished running before doing a module unload, because the module unload
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* itself uses stop_machine(), which insures that every preempt disabled section
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* have finished.
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*/
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int tracepoint_probe_unregister(const char *name, void *probe, void *data)
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{
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struct tracepoint_func *old;
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mutex_lock(&tracepoints_mutex);
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old = tracepoint_remove_probe(name, probe, data);
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mutex_unlock(&tracepoints_mutex);
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if (IS_ERR(old))
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return PTR_ERR(old);
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tracepoint_update_probes(); /* may update entry */
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release_probes(old);
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return 0;
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}
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EXPORT_SYMBOL_GPL(tracepoint_probe_unregister);
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static LIST_HEAD(old_probes);
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static int need_update;
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static void tracepoint_add_old_probes(void *old)
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{
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need_update = 1;
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if (old) {
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struct tp_probes *tp_probes = container_of(old,
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struct tp_probes, probes[0]);
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list_add(&tp_probes->u.list, &old_probes);
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}
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}
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/**
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* tracepoint_probe_register_noupdate - register a probe but not connect
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* @name: tracepoint name
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* @probe: probe handler
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*
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* caller must call tracepoint_probe_update_all()
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*/
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int tracepoint_probe_register_noupdate(const char *name, void *probe,
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void *data)
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{
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struct tracepoint_func *old;
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mutex_lock(&tracepoints_mutex);
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old = tracepoint_add_probe(name, probe, data);
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if (IS_ERR(old)) {
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mutex_unlock(&tracepoints_mutex);
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return PTR_ERR(old);
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}
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tracepoint_add_old_probes(old);
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mutex_unlock(&tracepoints_mutex);
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return 0;
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}
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EXPORT_SYMBOL_GPL(tracepoint_probe_register_noupdate);
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/**
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* tracepoint_probe_unregister_noupdate - remove a probe but not disconnect
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* @name: tracepoint name
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* @probe: probe function pointer
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*
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* caller must call tracepoint_probe_update_all()
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*/
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int tracepoint_probe_unregister_noupdate(const char *name, void *probe,
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void *data)
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{
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struct tracepoint_func *old;
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mutex_lock(&tracepoints_mutex);
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old = tracepoint_remove_probe(name, probe, data);
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if (IS_ERR(old)) {
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mutex_unlock(&tracepoints_mutex);
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return PTR_ERR(old);
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}
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tracepoint_add_old_probes(old);
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mutex_unlock(&tracepoints_mutex);
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return 0;
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}
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EXPORT_SYMBOL_GPL(tracepoint_probe_unregister_noupdate);
|
|
|
|
/**
|
|
* tracepoint_probe_update_all - update tracepoints
|
|
*/
|
|
void tracepoint_probe_update_all(void)
|
|
{
|
|
LIST_HEAD(release_probes);
|
|
struct tp_probes *pos, *next;
|
|
|
|
mutex_lock(&tracepoints_mutex);
|
|
if (!need_update) {
|
|
mutex_unlock(&tracepoints_mutex);
|
|
return;
|
|
}
|
|
if (!list_empty(&old_probes))
|
|
list_replace_init(&old_probes, &release_probes);
|
|
need_update = 0;
|
|
mutex_unlock(&tracepoints_mutex);
|
|
|
|
tracepoint_update_probes();
|
|
list_for_each_entry_safe(pos, next, &release_probes, u.list) {
|
|
list_del(&pos->u.list);
|
|
call_rcu_sched(&pos->u.rcu, rcu_free_old_probes);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(tracepoint_probe_update_all);
|
|
|
|
/**
|
|
* tracepoint_get_iter_range - Get a next tracepoint iterator given a range.
|
|
* @tracepoint: current tracepoints (in), next tracepoint (out)
|
|
* @begin: beginning of the range
|
|
* @end: end of the range
|
|
*
|
|
* Returns whether a next tracepoint has been found (1) or not (0).
|
|
* Will return the first tracepoint in the range if the input tracepoint is
|
|
* NULL.
|
|
*/
|
|
int tracepoint_get_iter_range(struct tracepoint * const **tracepoint,
|
|
struct tracepoint * const *begin, struct tracepoint * const *end)
|
|
{
|
|
if (!*tracepoint && begin != end) {
|
|
*tracepoint = begin;
|
|
return 1;
|
|
}
|
|
if (*tracepoint >= begin && *tracepoint < end)
|
|
return 1;
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(tracepoint_get_iter_range);
|
|
|
|
static void tracepoint_get_iter(struct tracepoint_iter *iter)
|
|
{
|
|
int found = 0;
|
|
|
|
/* Core kernel tracepoints */
|
|
if (!iter->module) {
|
|
found = tracepoint_get_iter_range(&iter->tracepoint,
|
|
__start___tracepoints_ptrs,
|
|
__stop___tracepoints_ptrs);
|
|
if (found)
|
|
goto end;
|
|
}
|
|
/* tracepoints in modules. */
|
|
found = module_get_iter_tracepoints(iter);
|
|
end:
|
|
if (!found)
|
|
tracepoint_iter_reset(iter);
|
|
}
|
|
|
|
void tracepoint_iter_start(struct tracepoint_iter *iter)
|
|
{
|
|
tracepoint_get_iter(iter);
|
|
}
|
|
EXPORT_SYMBOL_GPL(tracepoint_iter_start);
|
|
|
|
void tracepoint_iter_next(struct tracepoint_iter *iter)
|
|
{
|
|
iter->tracepoint++;
|
|
/*
|
|
* iter->tracepoint may be invalid because we blindly incremented it.
|
|
* Make sure it is valid by marshalling on the tracepoints, getting the
|
|
* tracepoints from following modules if necessary.
|
|
*/
|
|
tracepoint_get_iter(iter);
|
|
}
|
|
EXPORT_SYMBOL_GPL(tracepoint_iter_next);
|
|
|
|
void tracepoint_iter_stop(struct tracepoint_iter *iter)
|
|
{
|
|
}
|
|
EXPORT_SYMBOL_GPL(tracepoint_iter_stop);
|
|
|
|
void tracepoint_iter_reset(struct tracepoint_iter *iter)
|
|
{
|
|
iter->module = NULL;
|
|
iter->tracepoint = NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(tracepoint_iter_reset);
|
|
|
|
#ifdef CONFIG_MODULES
|
|
|
|
int tracepoint_module_notify(struct notifier_block *self,
|
|
unsigned long val, void *data)
|
|
{
|
|
struct module *mod = data;
|
|
|
|
switch (val) {
|
|
case MODULE_STATE_COMING:
|
|
case MODULE_STATE_GOING:
|
|
tracepoint_update_probe_range(mod->tracepoints_ptrs,
|
|
mod->tracepoints_ptrs + mod->num_tracepoints);
|
|
break;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
struct notifier_block tracepoint_module_nb = {
|
|
.notifier_call = tracepoint_module_notify,
|
|
.priority = 0,
|
|
};
|
|
|
|
static int init_tracepoints(void)
|
|
{
|
|
return register_module_notifier(&tracepoint_module_nb);
|
|
}
|
|
__initcall(init_tracepoints);
|
|
|
|
#endif /* CONFIG_MODULES */
|
|
|
|
#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
|
|
|
|
/* NB: reg/unreg are called while guarded with the tracepoints_mutex */
|
|
static int sys_tracepoint_refcount;
|
|
|
|
void syscall_regfunc(void)
|
|
{
|
|
unsigned long flags;
|
|
struct task_struct *g, *t;
|
|
|
|
if (!sys_tracepoint_refcount) {
|
|
read_lock_irqsave(&tasklist_lock, flags);
|
|
do_each_thread(g, t) {
|
|
/* Skip kernel threads. */
|
|
if (t->mm)
|
|
set_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
|
|
} while_each_thread(g, t);
|
|
read_unlock_irqrestore(&tasklist_lock, flags);
|
|
}
|
|
sys_tracepoint_refcount++;
|
|
}
|
|
|
|
void syscall_unregfunc(void)
|
|
{
|
|
unsigned long flags;
|
|
struct task_struct *g, *t;
|
|
|
|
sys_tracepoint_refcount--;
|
|
if (!sys_tracepoint_refcount) {
|
|
read_lock_irqsave(&tasklist_lock, flags);
|
|
do_each_thread(g, t) {
|
|
clear_tsk_thread_flag(t, TIF_SYSCALL_TRACEPOINT);
|
|
} while_each_thread(g, t);
|
|
read_unlock_irqrestore(&tasklist_lock, flags);
|
|
}
|
|
}
|
|
#endif
|