On 03/21/2014 12:31 AM, Pavel Emelyanov wrote:
On 03/20/2014 01:39 PM, Janani Venkataraman wrote:
Getting number of threads and their respective IDs through /proc/pid/stat and
/proc/pid/task.
The threads are then seized and interrupted. After the dump is taken they are
detached.
Signed-off-by: Janani Venkataraman <janan...@linux.vnet.ibm.com>
---
+/* Gets the Thread IDS and siezes them */
+int seize_threads(int pid)
+{
+ char filename[40];
+ DIR *dir;
+ int ct = 0, ret = 0, tmp_tid;
+ struct dirent *entry;
+ char state;
+
+ ret = get_thread_count(pid);
+ if (ret == -1)
+ return -1;
+
+ cp.thread_count = ret;
+ cp.t_id = calloc(cp.thread_count, sizeof(int));
+ if (!cp.t_id) {
+ status = errno;
+ gencore_log("Could not allocate memory for thread_ids.\n");
+ return -1;
+ }
+
+ snprintf(filename, 40, "/proc/%d/task", pid);
+ dir = opendir(filename);
+
+ while ((entry = readdir(dir))) {
This simple loop is not enough -- threads may appear and disappear while
you do the readdir and seize, so you should scan it several times to
make sure you caught all the threads.
I will look into this.
You can look at how this is done in CRIU in cr-dump,c:collect_threads().
Yes I will look into that function. Thanks.
Thanks.
Janani
+ if (entry->d_type == DT_DIR && entry->d_name[0] != '.') {
+ tmp_tid = atoi(entry->d_name);
+ ret = ptrace(PTRACE_SEIZE, tmp_tid, 0, 0);
+ if (ret) {
+ state = get_thread_status(tmp_tid);
+ if (state == 'Z')
+ goto assign;
+ status = errno;
+ gencore_log("Could not seize thread: %d\n",
+ tmp_tid);
+ break;
+ }
+ ret = ptrace(PTRACE_INTERRUPT, tmp_tid, 0, 0);
+ if (ret) {
+ state = get_thread_status(tmp_tid);
+ if (state == 'Z')
+ goto assign;
+ status = errno;
+ gencore_log("Could not interrupt thread: %d\n",
+ tmp_tid);
+ break;
+ }
+assign:
+ /* If a new thread, is created after we fetch the
thread_count,
+ * we may encounter a buffer overflow situation in the
cp_tid.
+ * Hence we check this case and re-allocate memory if
required.
+ */
+ cp.t_id[ct++] = tmp_tid;
+ }
+ }
+
+ /* Reassigning based on successful seizes */
+ cp.thread_count = ct;
+
+ closedir(dir);
+
+ /* Successful seize and interrupt on all threads makes ret = 0 */
+ return ret;
+}
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