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Print thread name when dumping backtrace #6

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Print thread name when dumping backtrace #6

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87b8238
Print thread name when dumping backtrace
nslowell Jun 20, 2016
eff3adb
Cleaner string handling and printing of process comm
nslowell Jun 27, 2016
1a15b0d
Standardize right side padding when printing thread names
nslowell Jun 27, 2016
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26 changes: 21 additions & 5 deletions src/backtrace.c
100644 → 100755
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Original file line number Diff line number Diff line change
Expand Up @@ -103,13 +103,21 @@ int backtrace_snapshot(int pid, int *tids, int *index, int nr_tids)
{
int i, rc = 0;
struct snapshot *snap;

if ((snap = get_snapshot(pid, tids, index, nr_tids)) == NULL)
return -1;

for (i = 0; i < snap->num_threads; ++i) {
printf("-------------------- thread %d (%d) --------------------\n",
(index != NULL ? index[i] : i+1), snap->tids[i]);
int x;
char comm[16];
char end_pad[25] = "------------------------";

x = get_thread_comm(snap->tids[i], comm, sizeof(comm));
if (x > 0 && x <= sizeof(end_pad))
{
end_pad[sizeof(end_pad) - x] = '\0';
printf("-------------- thread %d (%d) (%s) %s\n", (index != NULL ? index[i] : i+1), snap->tids[i], comm, end_pad);
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@v-nikulichev v-nikulichev Jun 20, 2017

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If get_thread_num() fails for some reason, or the name is too long, the header is not printed at all. This is quite wrong. In case of error it should be indicated in some simple way (like we do when a file is deleted). If the name is too long, we can truncate it.

}

snap->cur_thr = i;
if (backtrace_thread(&snapshot_addr_space_accessors, snap) < 0)
Expand Down Expand Up @@ -144,9 +152,17 @@ int backtrace_ptrace(int pid, int *tids, int *index, int nr_tids)

for (i = 0; i < count; ++i) {
void *upt_info;
int x;
char comm[16];
char end_pad[25] = "------------------------";

printf("-------------------- thread %d (%d) --------------------\n",
(index != NULL ? index[i] : i+1), threads[i]);
x = get_thread_comm(threads[i], comm, sizeof(comm));

if (x > 0 && x <= sizeof(end_pad))
{
end_pad[sizeof(end_pad) - x] = '\0';
printf("-------------- thread %d (%d) (%s) %s\n", (index != NULL ? index[i] : i + 1), threads[i], comm, end_pad);
}

if (threads[i] != pid && attach_thread(threads[i]) < 0) {
rc = -1;
Expand Down
34 changes: 34 additions & 0 deletions src/proc.c
100644 → 100755
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Expand Up @@ -34,6 +34,9 @@

#define SLEEP_WAIT 500

#define MAX(a,b) ((a) > (b) ? a : b)
#define MIN(a,b) ((a) < (b) ? a : b)

int attached_pid = 0;

/* timeout on waiting for process to stop (us) */
Expand Down Expand Up @@ -191,6 +194,37 @@ int print_proc_maps(int pid)
return system(cmd);
}

int get_thread_comm(int pid, char * dst, size_t n)
{
FILE *f;
char buf[32];
int i, x;
int rc = -1;

if (dst == NULL)
{
return -1;
}

snprintf(buf, sizeof(buf), "/proc/%d/comm", pid);
if ((f = fopen(buf, "r")) == NULL) {
fprintf(stderr, "cannot open %s: %s\n", buf, strerror(errno));
return -1;
}

if (fgets(buf, sizeof(buf), f)) {
i = strcspn(buf, "\n");
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@v-nikulichev v-nikulichev Jun 24, 2016

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You don't need to put terminator by hand. fgets() does it. From GETS(3):

fgets() reads in at most one less than size characters from stream and stores them into the buffer pointed to by s. Reading stops after an EOF or a newline. If a newline is read, it is stored into the buffer. A terminating null byte ('\0') is stored after the last character in the buffer.

buf[i] = '\0';
x = MAX(MIN(n, i+1), 1);
strncpy(dst, buf, x);
dst[x-1] = '\0';
rc = x;
}

fclose(f);
return rc;
}

/*
* filter for scandir(). choose only thread identifiers
*/
Expand Down
5 changes: 5 additions & 0 deletions src/proc.h
100644 → 100755
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,11 @@ struct mem_map *create_maps(int pid);
*/
int print_proc_maps(int pid);

/*
* copy pid process comm into dst string, up to n characters
*/
int get_thread_comm(int pid, char * dst, size_t n);

/*
* get thread identifiers of the process
*/
Expand Down