linux/tools/perf/util/thread.c
Kan Liang ff165628d7 perf callchain: Stitch LBR call stack
In LBR call stack mode, the depth of reconstructed LBR call stack limits
to the number of LBR registers.

  For example, on skylake, the depth of reconstructed LBR call stack is
  always <= 32.

  # To display the perf.data header info, please use
  # --header/--header-only options.
  #
  #
  # Total Lost Samples: 0
  #
  # Samples: 6K of event 'cycles'
  # Event count (approx.): 6487119731
  #
  # Children      Self  Command          Shared Object       Symbol
  # ........  ........  ...............  ..................
  # ................................

    99.97%    99.97%  tchain_edit      tchain_edit        [.] f43
            |
             --99.64%--f11
                       f12
                       f13
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                       f20
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                       f23
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                       f32
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                       f43

For a call stack which is deeper than LBR limit, HW will overwrite the
LBR register with oldest branch. Only partial call stacks can be
reconstructed.

However, the overwritten LBRs may still be retrieved from previous
sample. At that moment, HW hasn't overwritten the LBR registers yet.
Perf tools can stitch those overwritten LBRs on current call stacks to
get a more complete call stack.

To determine if LBRs can be stitched, perf tools need to compare current
sample with previous sample.

- They should have identical LBR records (Same from, to and flags
  values, and the same physical index of LBR registers).

- The searching starts from the base-of-stack of current sample.

Once perf determines to stitch the previous LBRs, the corresponding LBR
cursor nodes will be copied to 'lists'.  The 'lists' is to track the LBR
cursor nodes which are going to be stitched.

When the stitching is over, the nodes will not be freed immediately.
They will be moved to 'free_lists'. Next stitching may reuse the space.
Both 'lists' and 'free_lists' will be freed when all samples are
processed.

Committer notes:

Fix the intel-pt.c initialization of the union with 'struct
branch_flags', that breaks the build with its unnamed union on older gcc
versions.

Uninline thread__free_stitch_list(), as it grew big and started dragging
includes to thread.h, so move it to thread.c where what it needs in
terms of headers are already there.

This fixes the build in several systems such as debian:experimental when
cross building to the MIPS32 architecture, i.e. in the other cases what
was needed was being included by sheer luck.

  In file included from builtin-sched.c:11:
  util/thread.h: In function 'thread__free_stitch_list':
  util/thread.h:169:3: error: implicit declaration of function 'free' [-Werror=implicit-function-declaration]
    169 |   free(pos);
        |   ^~~~
  util/thread.h:169:3: error: incompatible implicit declaration of built-in function 'free' [-Werror]
  util/thread.h:19:1: note: include '<stdlib.h>' or provide a declaration of 'free'
     18 | #include "callchain.h"
    +++ |+#include <stdlib.h>
     19 |
  util/thread.h:174:3: error: incompatible implicit declaration of built-in function 'free' [-Werror]
    174 |   free(pos);
        |   ^~~~
  util/thread.h:174:3: note: include '<stdlib.h>' or provide a declaration of 'free'

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Pavel Gerasimov <pavel.gerasimov@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Vitaly Slobodskoy <vitaly.slobodskoy@intel.com>
Link: http://lore.kernel.org/lkml/20200319202517.23423-13-kan.liang@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-04-18 09:05:01 -03:00

479 lines
11 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <linux/kernel.h>
#include <linux/zalloc.h>
#include "dso.h"
#include "session.h"
#include "thread.h"
#include "thread-stack.h"
#include "debug.h"
#include "namespaces.h"
#include "comm.h"
#include "map.h"
#include "symbol.h"
#include "unwind.h"
#include "callchain.h"
#include <api/fs/fs.h>
int thread__init_maps(struct thread *thread, struct machine *machine)
{
pid_t pid = thread->pid_;
if (pid == thread->tid || pid == -1) {
thread->maps = maps__new(machine);
} else {
struct thread *leader = __machine__findnew_thread(machine, pid, pid);
if (leader) {
thread->maps = maps__get(leader->maps);
thread__put(leader);
}
}
return thread->maps ? 0 : -1;
}
struct thread *thread__new(pid_t pid, pid_t tid)
{
char *comm_str;
struct comm *comm;
struct thread *thread = zalloc(sizeof(*thread));
if (thread != NULL) {
thread->pid_ = pid;
thread->tid = tid;
thread->ppid = -1;
thread->cpu = -1;
thread->lbr_stitch_enable = false;
INIT_LIST_HEAD(&thread->namespaces_list);
INIT_LIST_HEAD(&thread->comm_list);
init_rwsem(&thread->namespaces_lock);
init_rwsem(&thread->comm_lock);
comm_str = malloc(32);
if (!comm_str)
goto err_thread;
snprintf(comm_str, 32, ":%d", tid);
comm = comm__new(comm_str, 0, false);
free(comm_str);
if (!comm)
goto err_thread;
list_add(&comm->list, &thread->comm_list);
refcount_set(&thread->refcnt, 1);
RB_CLEAR_NODE(&thread->rb_node);
/* Thread holds first ref to nsdata. */
thread->nsinfo = nsinfo__new(pid);
srccode_state_init(&thread->srccode_state);
}
return thread;
err_thread:
free(thread);
return NULL;
}
void thread__delete(struct thread *thread)
{
struct namespaces *namespaces, *tmp_namespaces;
struct comm *comm, *tmp_comm;
BUG_ON(!RB_EMPTY_NODE(&thread->rb_node));
thread_stack__free(thread);
if (thread->maps) {
maps__put(thread->maps);
thread->maps = NULL;
}
down_write(&thread->namespaces_lock);
list_for_each_entry_safe(namespaces, tmp_namespaces,
&thread->namespaces_list, list) {
list_del_init(&namespaces->list);
namespaces__free(namespaces);
}
up_write(&thread->namespaces_lock);
down_write(&thread->comm_lock);
list_for_each_entry_safe(comm, tmp_comm, &thread->comm_list, list) {
list_del_init(&comm->list);
comm__free(comm);
}
up_write(&thread->comm_lock);
nsinfo__zput(thread->nsinfo);
srccode_state_free(&thread->srccode_state);
exit_rwsem(&thread->namespaces_lock);
exit_rwsem(&thread->comm_lock);
thread__free_stitch_list(thread);
free(thread);
}
struct thread *thread__get(struct thread *thread)
{
if (thread)
refcount_inc(&thread->refcnt);
return thread;
}
void thread__put(struct thread *thread)
{
if (thread && refcount_dec_and_test(&thread->refcnt)) {
/*
* Remove it from the dead threads list, as last reference is
* gone, if it is in a dead threads list.
*
* We may not be there anymore if say, the machine where it was
* stored was already deleted, so we already removed it from
* the dead threads and some other piece of code still keeps a
* reference.
*
* This is what 'perf sched' does and finally drops it in
* perf_sched__lat(), where it calls perf_sched__read_events(),
* that processes the events by creating a session and deleting
* it, which ends up destroying the list heads for the dead
* threads, but before it does that it removes all threads from
* it using list_del_init().
*
* So we need to check here if it is in a dead threads list and
* if so, remove it before finally deleting the thread, to avoid
* an use after free situation.
*/
if (!list_empty(&thread->node))
list_del_init(&thread->node);
thread__delete(thread);
}
}
static struct namespaces *__thread__namespaces(const struct thread *thread)
{
if (list_empty(&thread->namespaces_list))
return NULL;
return list_first_entry(&thread->namespaces_list, struct namespaces, list);
}
struct namespaces *thread__namespaces(struct thread *thread)
{
struct namespaces *ns;
down_read(&thread->namespaces_lock);
ns = __thread__namespaces(thread);
up_read(&thread->namespaces_lock);
return ns;
}
static int __thread__set_namespaces(struct thread *thread, u64 timestamp,
struct perf_record_namespaces *event)
{
struct namespaces *new, *curr = __thread__namespaces(thread);
new = namespaces__new(event);
if (!new)
return -ENOMEM;
list_add(&new->list, &thread->namespaces_list);
if (timestamp && curr) {
/*
* setns syscall must have changed few or all the namespaces
* of this thread. Update end time for the namespaces
* previously used.
*/
curr = list_next_entry(new, list);
curr->end_time = timestamp;
}
return 0;
}
int thread__set_namespaces(struct thread *thread, u64 timestamp,
struct perf_record_namespaces *event)
{
int ret;
down_write(&thread->namespaces_lock);
ret = __thread__set_namespaces(thread, timestamp, event);
up_write(&thread->namespaces_lock);
return ret;
}
struct comm *thread__comm(const struct thread *thread)
{
if (list_empty(&thread->comm_list))
return NULL;
return list_first_entry(&thread->comm_list, struct comm, list);
}
struct comm *thread__exec_comm(const struct thread *thread)
{
struct comm *comm, *last = NULL, *second_last = NULL;
list_for_each_entry(comm, &thread->comm_list, list) {
if (comm->exec)
return comm;
second_last = last;
last = comm;
}
/*
* 'last' with no start time might be the parent's comm of a synthesized
* thread (created by processing a synthesized fork event). For a main
* thread, that is very probably wrong. Prefer a later comm to avoid
* that case.
*/
if (second_last && !last->start && thread->pid_ == thread->tid)
return second_last;
return last;
}
static int ____thread__set_comm(struct thread *thread, const char *str,
u64 timestamp, bool exec)
{
struct comm *new, *curr = thread__comm(thread);
/* Override the default :tid entry */
if (!thread->comm_set) {
int err = comm__override(curr, str, timestamp, exec);
if (err)
return err;
} else {
new = comm__new(str, timestamp, exec);
if (!new)
return -ENOMEM;
list_add(&new->list, &thread->comm_list);
if (exec)
unwind__flush_access(thread->maps);
}
thread->comm_set = true;
return 0;
}
int __thread__set_comm(struct thread *thread, const char *str, u64 timestamp,
bool exec)
{
int ret;
down_write(&thread->comm_lock);
ret = ____thread__set_comm(thread, str, timestamp, exec);
up_write(&thread->comm_lock);
return ret;
}
int thread__set_comm_from_proc(struct thread *thread)
{
char path[64];
char *comm = NULL;
size_t sz;
int err = -1;
if (!(snprintf(path, sizeof(path), "%d/task/%d/comm",
thread->pid_, thread->tid) >= (int)sizeof(path)) &&
procfs__read_str(path, &comm, &sz) == 0) {
comm[sz - 1] = '\0';
err = thread__set_comm(thread, comm, 0);
}
return err;
}
static const char *__thread__comm_str(const struct thread *thread)
{
const struct comm *comm = thread__comm(thread);
if (!comm)
return NULL;
return comm__str(comm);
}
const char *thread__comm_str(struct thread *thread)
{
const char *str;
down_read(&thread->comm_lock);
str = __thread__comm_str(thread);
up_read(&thread->comm_lock);
return str;
}
/* CHECKME: it should probably better return the max comm len from its comm list */
int thread__comm_len(struct thread *thread)
{
if (!thread->comm_len) {
const char *comm = thread__comm_str(thread);
if (!comm)
return 0;
thread->comm_len = strlen(comm);
}
return thread->comm_len;
}
size_t thread__fprintf(struct thread *thread, FILE *fp)
{
return fprintf(fp, "Thread %d %s\n", thread->tid, thread__comm_str(thread)) +
maps__fprintf(thread->maps, fp);
}
int thread__insert_map(struct thread *thread, struct map *map)
{
int ret;
ret = unwind__prepare_access(thread->maps, map, NULL);
if (ret)
return ret;
maps__fixup_overlappings(thread->maps, map, stderr);
maps__insert(thread->maps, map);
return 0;
}
static int __thread__prepare_access(struct thread *thread)
{
bool initialized = false;
int err = 0;
struct maps *maps = thread->maps;
struct map *map;
down_read(&maps->lock);
maps__for_each_entry(maps, map) {
err = unwind__prepare_access(thread->maps, map, &initialized);
if (err || initialized)
break;
}
up_read(&maps->lock);
return err;
}
static int thread__prepare_access(struct thread *thread)
{
int err = 0;
if (dwarf_callchain_users)
err = __thread__prepare_access(thread);
return err;
}
static int thread__clone_maps(struct thread *thread, struct thread *parent, bool do_maps_clone)
{
/* This is new thread, we share map groups for process. */
if (thread->pid_ == parent->pid_)
return thread__prepare_access(thread);
if (thread->maps == parent->maps) {
pr_debug("broken map groups on thread %d/%d parent %d/%d\n",
thread->pid_, thread->tid, parent->pid_, parent->tid);
return 0;
}
/* But this one is new process, copy maps. */
return do_maps_clone ? maps__clone(thread, parent->maps) : 0;
}
int thread__fork(struct thread *thread, struct thread *parent, u64 timestamp, bool do_maps_clone)
{
if (parent->comm_set) {
const char *comm = thread__comm_str(parent);
int err;
if (!comm)
return -ENOMEM;
err = thread__set_comm(thread, comm, timestamp);
if (err)
return err;
}
thread->ppid = parent->tid;
return thread__clone_maps(thread, parent, do_maps_clone);
}
void thread__find_cpumode_addr_location(struct thread *thread, u64 addr,
struct addr_location *al)
{
size_t i;
const u8 cpumodes[] = {
PERF_RECORD_MISC_USER,
PERF_RECORD_MISC_KERNEL,
PERF_RECORD_MISC_GUEST_USER,
PERF_RECORD_MISC_GUEST_KERNEL
};
for (i = 0; i < ARRAY_SIZE(cpumodes); i++) {
thread__find_symbol(thread, cpumodes[i], addr, al);
if (al->map)
break;
}
}
struct thread *thread__main_thread(struct machine *machine, struct thread *thread)
{
if (thread->pid_ == thread->tid)
return thread__get(thread);
if (thread->pid_ == -1)
return NULL;
return machine__find_thread(machine, thread->pid_, thread->pid_);
}
int thread__memcpy(struct thread *thread, struct machine *machine,
void *buf, u64 ip, int len, bool *is64bit)
{
u8 cpumode = PERF_RECORD_MISC_USER;
struct addr_location al;
long offset;
if (machine__kernel_ip(machine, ip))
cpumode = PERF_RECORD_MISC_KERNEL;
if (!thread__find_map(thread, cpumode, ip, &al) || !al.map->dso ||
al.map->dso->data.status == DSO_DATA_STATUS_ERROR ||
map__load(al.map) < 0)
return -1;
offset = al.map->map_ip(al.map, ip);
if (is64bit)
*is64bit = al.map->dso->is_64_bit;
return dso__data_read_offset(al.map->dso, machine, offset, buf, len);
}
void thread__free_stitch_list(struct thread *thread)
{
struct lbr_stitch *lbr_stitch = thread->lbr_stitch;
struct stitch_list *pos, *tmp;
if (!lbr_stitch)
return;
list_for_each_entry_safe(pos, tmp, &lbr_stitch->lists, node) {
list_del_init(&pos->node);
free(pos);
}
list_for_each_entry_safe(pos, tmp, &lbr_stitch->free_lists, node) {
list_del_init(&pos->node);
free(pos);
}
zfree(&lbr_stitch->prev_lbr_cursor);
zfree(&thread->lbr_stitch);
}