Skip to content

Commit

Permalink
retsnoop: handle idle threads properly
Browse files Browse the repository at this point in the history 
Idle threads all have PID 0, one idle thread per each CPU. This screws
up retsnoop's logic around using PID as a unique session ID. So for idle
threads, use -(1 + CPU ID) as a session (session ID 0 will be reserved
as invalid).

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
  • Loading branch information
@anakryiko
anakryiko committed Aug 28, 2024
1 parent 91bac51 commit 47a2ef6
Show file tree
Hide file tree
Showing 5 changed files with 75 additions and 60 deletions.
2 changes: 1 addition & 1 deletion src/fnargs.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -997,7 +997,7 @@ int prepare_ctx_args_specs(int probe_id, const struct inj_probe_info *inj)
{
struct ctx_args_info *ctx_args;
char desc[256];
int i, err;
int i, err = -EINVAL;

snprintf_inj_probe(desc, sizeof(desc), inj);

Expand Down
52 changes: 27 additions & 25 deletions src/logic.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -64,26 +64,27 @@ static void free_sessions(void)
hashmap__clear(&sessions_hash);
}

static void purge_session(struct ctx *ctx, int pid)
static void purge_session(struct ctx *ctx, int sess_id)
{
struct session *sess;

if (hashmap__delete(&sessions_hash, (long)pid, NULL, &sess))
if (hashmap__delete(&sessions_hash, (long)sess_id, NULL, &sess))
free_session(sess);
}

static int handle_session_start(struct ctx *ctx, const struct rec_session_start *r)
{
struct session *sess;

purge_session(ctx, r->pid);
purge_session(ctx, r->sess_id);

sess = calloc(1, sizeof(*sess));
if (!sess || hashmap__add(&sessions_hash, (long)r->pid, sess)) {
fprintf(stderr, "Failed to allocate memory for session PID %d!\n", r->pid);
if (!sess || hashmap__add(&sessions_hash, (long)r->sess_id, sess)) {
elog("Failed to allocate memory for session %d (PID %d)!\n", r->sess_id, r->pid);
return -ENOMEM;
}

sess->sess_id = r->sess_id;
sess->pid = r->pid;
sess->tgid = r->tgid;
sess->start_ts = r->start_ts;
Expand All @@ -96,7 +97,7 @@ static int handle_session_start(struct ctx *ctx, const struct rec_session_start
static int handle_lbr_stack(struct ctx *dctx, struct session *sess, const struct rec_lbr_stack *r)
{
if (sess->lbrs) {
fprintf(stderr, "BUG: PID %d session data contains LBR data already!\n", r->pid);
elog("BUG: SESSION %d data contains LBR data already!\n", r->sess_id);
return -EINVAL;
}

Expand All @@ -105,7 +106,7 @@ static int handle_lbr_stack(struct ctx *dctx, struct session *sess, const struct
if (sess->lbrs_sz > 0) {
sess->lbrs = malloc(sess->lbrs_sz);
if (!sess->lbrs) {
fprintf(stderr, "SESSION PID %d: failed to allocate LBR memory: %d\n", r->pid, -ENOMEM);
elog("SESSION %d: failed to allocate LBR memory: %d\n", r->sess_id, -ENOMEM);
return -ENOMEM;
}
memcpy(sess->lbrs, r->lbrs, sess->lbrs_sz);
Expand Down Expand Up @@ -669,7 +670,7 @@ static struct func_args_item *find_fnargs_item(const struct session *sess, int s
}

static void prepare_trace_items(struct ctx *ctx, struct stack_items_cache *cache,
int pid, int last_seq_id)
int sess_id, int last_seq_id)
{
const struct mass_attacher_func_info *finfo;
const struct inj_probe_info *inj;
Expand All @@ -680,7 +681,7 @@ static void prepare_trace_items(struct ctx *ctx, struct stack_items_cache *cache
int i, d, prev_seq_id = -1, orig_seq_id;
int args_idx = 0, ctx_idx = 0;

if (!hashmap__find(&sessions_hash, (long)pid, &sess))
if (!hashmap__find(&sessions_hash, (long)sess_id, &sess))
return;

cache->cnt = 0;
Expand Down Expand Up @@ -1260,9 +1261,10 @@ static int handle_session_end(struct ctx *dctx, struct session *sess,
goto out_purge;

if (env.debug) {
printf("GOT %s STACK (depth %u):\n", s->is_err ? "ERROR" : "SUCCESS", s->max_depth);
printf("SESSION %d GOT %s STACK (depth %u):\n",
sess->sess_id, s->is_err ? "ERROR" : "SUCCESS", s->max_depth);
printf("DEPTH %d MAX DEPTH %d SAVED DEPTH %d MAX SAVED DEPTH %d\n",
s->depth, s->max_depth, s->saved_depth, s->saved_max_depth);
s->depth, s->max_depth, s->saved_depth, s->saved_max_depth);
}

ts_to_str(ktime_to_ts(sess->start_ts), ts1, sizeof(ts1));
Expand All @@ -1279,7 +1281,7 @@ static int handle_session_end(struct ctx *dctx, struct session *sess,
* call stack trace (depth == 0)
*/
if (env.emit_func_trace && s->depth == 0) {
prepare_trace_items(dctx, &stack_items1, sess->pid, r->last_seq_id);
prepare_trace_items(dctx, &stack_items1, sess->sess_id, r->last_seq_id);
print_trace_items(dctx, &stack_items1);
}

Expand Down Expand Up @@ -1336,7 +1338,7 @@ static int handle_session_end(struct ctx *dctx, struct session *sess,
printf("\n\n");

out_purge:
purge_session(dctx, r->pid);
purge_session(dctx, r->sess_id);

return ret;
}
Expand All @@ -1361,8 +1363,8 @@ int handle_event(void *ctx, void *data, size_t data_sz)
case REC_FUNC_TRACE_EXIT: {
const struct rec_func_trace_entry *r = data;

if (!hashmap__find(&sessions_hash, (long)r->pid, &sess)) {
fprintf(stderr, "BUG: PID %d session data not found (%s)!\n", r->pid,
if (!hashmap__find(&sessions_hash, (long)r->sess_id, &sess)) {
fprintf(stderr, "BUG: Session %d data not found (%s)!\n", r->sess_id,
r->type == REC_FUNC_TRACE_ENTRY ? "FUNC_TRACE_ENTRY" : "FUNC_TRACE_EXIT");
return -EINVAL;
}
Expand All @@ -1371,44 +1373,44 @@ int handle_event(void *ctx, void *data, size_t data_sz)
case REC_FNARGS_CAPTURE: {
struct rec_fnargs_capture *r = data;

if (!hashmap__find(&sessions_hash, (long)r->pid, &sess)) {
fprintf(stderr, "BUG: PID %d session data not found (FUNC_ARGS_CAPTURE)!\n", r->pid);
if (!hashmap__find(&sessions_hash, (long)r->sess_id, &sess)) {
fprintf(stderr, "BUG: SESSION %d session data not found (FUNC_ARGS_CAPTURE)!\n", r->sess_id);
return -EINVAL;
}
return handle_fnargs_capture(ctx, sess, r);
}
case REC_LBR_STACK: {
const struct rec_lbr_stack *r = data;

if (!hashmap__find(&sessions_hash, (long)r->pid, &sess)) {
fprintf(stderr, "BUG: PID %d session data not found (LBR_STACK)!\n", r->pid);
if (!hashmap__find(&sessions_hash, (long)r->sess_id, &sess)) {
fprintf(stderr, "BUG: SESSION %d session data not found (LBR_STACK)!\n", r->sess_id);
return -EINVAL;
}
return handle_lbr_stack(ctx, sess, r);
}
case REC_INJ_PROBE: {
const struct rec_inj_probe *r = data;

if (!hashmap__find(&sessions_hash, (long)r->pid, &sess)) {
fprintf(stderr, "BUG: PID %d session data not found (INJ_PROBE)!\n", r->pid);
if (!hashmap__find(&sessions_hash, (long)r->sess_id, &sess)) {
fprintf(stderr, "BUG: SESSION %d session data not found (INJ_PROBE)!\n", r->sess_id);
return -EINVAL;
}
return handle_inj_probe(ctx, sess, r);
}
case REC_CTXARGS_CAPTURE: {
const struct rec_ctxargs_capture *r = data;

if (!hashmap__find(&sessions_hash, (long)r->pid, &sess)) {
fprintf(stderr, "BUG: PID %d session data not found (CTX_CAPTURE)!\n", r->pid);
if (!hashmap__find(&sessions_hash, (long)r->sess_id, &sess)) {
fprintf(stderr, "BUG: SESSION %d session data not found (CTX_CAPTURE)!\n", r->sess_id);
return -EINVAL;
}
return handle_ctx_capture(ctx, sess, r);
}
case REC_SESSION_END: {
const struct rec_session_end *r = data;

if (!hashmap__find(&sessions_hash, (long)r->pid, &sess)) {
fprintf(stderr, "BUG: PID %d session data not found (SESSION_END)!\n", r->pid);
if (!hashmap__find(&sessions_hash, (long)r->sess_id, &sess)) {
fprintf(stderr, "BUG: SESSION %d session data not found (SESSION_END)!\n", r->sess_id);
return -EINVAL;
}
return handle_session_end(ctx, sess, r);
Expand Down
1 change: 1 addition & 0 deletions src/logic.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,7 @@ struct trace_item {
};

struct session {
int sess_id;
int pid;
int tgid;
uint64_t start_ts;
Expand Down
Loading

0 comments on commit 47a2ef6

Please sign in to comment.