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 <jananive@xxxxxxxxxxxxxxxxxx> --- +/* 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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