* defs.h: Add new struct tcb fields: wait_status, next_need_service.
make flags field wider (ints are easier to work with on many CPUs). * strace.c (trace): Split this function into two: collect_stopped_tcbs() and handle_stopped_tcbs(). Now we collect *all* waitable tasks, then handle them all, then repeat. Fixes RH#478419 "Some threads stop when strace with -f option is executed on a multi-thread process" * test/many_looping_threads.c: example program which cna't be straced successfully without this fix.
This commit is contained in:
Denys Vlasenko
parent
ef2fbf856c
commit
215cc27037
13
ChangeLog
13
ChangeLog
@ -1,3 +1,16 @@
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2009-01-09 Denys Vlasenko <dvlasenk@redhat.com>
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* defs.h: Add new struct tcb fields: wait_status, next_need_service.
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make flags field wider (ints are easier to work with on many CPUs).
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* strace.c (trace): Split this function into two:
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collect_stopped_tcbs() and handle_stopped_tcbs().
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Now we collect *all* waitable tasks, then handle them all,
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then repeat.
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Fixes RH#478419 "Some threads stop when strace with -f option
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is executed on a multi-thread process"
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* test/many_looping_threads.c: example program which cna't be straced
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successfully without this fix.
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2009-01-06 Denys Vlasenko <dvlasenk@redhat.com>
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Output format fixes, improving the situation after recent
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5
defs.h
5
defs.h
@ -298,8 +298,11 @@ extern int mp_ioctl (int f, int c, void *a, int s);
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/* Trace Control Block */
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struct tcb {
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short flags; /* See below for TCB_ values */
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int flags; /* See below for TCB_ values */
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int pid; /* Process Id of this entry */
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int wait_status; /* Status from last wait() */
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struct tcb *next_need_service;
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/* Linked list of tracees found by wait()s */
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long scno; /* System call number */
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int u_nargs; /* System call arguments */
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long u_arg[MAX_ARGS]; /* System call arguments */
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116
strace.c
116
strace.c
@ -2268,8 +2268,8 @@ handle_group_exit(struct tcb *tcp, int sig)
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}
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#endif
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static int
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trace()
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static struct tcb *
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collect_stopped_tcbs(void)
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{
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int pid;
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int wait_errno;
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@ -2277,38 +2277,35 @@ trace()
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struct tcb *tcp;
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#ifdef LINUX
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struct rusage ru;
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struct rusage* ru_ptr = cflag ? &ru : NULL;
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int wnohang = 0;
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struct tcb *found_tcps = NULL;
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#ifdef __WALL
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static int wait4_options = __WALL;
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int wait4_options = __WALL;
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#endif
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#endif /* LINUX */
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while (nprocs != 0) {
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if (interrupted)
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return 0;
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if (interactive)
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sigprocmask(SIG_SETMASK, &empty_set, NULL);
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while (1) {
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#ifdef LINUX
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#ifdef __WALL
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pid = wait4(-1, &status, wait4_options, cflag ? &ru : NULL);
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pid = wait4(-1, &status, wait4_options | wnohang, ru_ptr);
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if (pid < 0 && (wait4_options & __WALL) && errno == EINVAL) {
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/* this kernel does not support __WALL */
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wait4_options &= ~__WALL;
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errno = 0;
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pid = wait4(-1, &status, wait4_options,
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cflag ? &ru : NULL);
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pid = wait4(-1, &status, wait4_options | wnohang, ru_ptr);
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}
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if (pid < 0 && !(wait4_options & __WALL) && errno == ECHILD) {
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/* most likely a "cloned" process */
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pid = wait4(-1, &status, __WCLONE,
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cflag ? &ru : NULL);
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if (pid == -1) {
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fprintf(stderr, "strace: clone wait4 "
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pid = wait4(-1, &status, __WCLONE | wnohang, ru_ptr);
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if (pid < 0 && errno != ECHILD) {
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fprintf(stderr, "strace: wait4(WCLONE) "
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"failed: %s\n", strerror(errno));
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}
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}
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#else
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pid = wait4(-1, &status, 0, cflag ? &ru : NULL);
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#endif /* __WALL */
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#else /* !__WALL */
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pid = wait4(-1, &status, wnohang, ru_ptr);
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#endif
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#endif /* LINUX */
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#ifdef SUNOS4
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pid = wait(&status);
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@ -2317,6 +2314,15 @@ trace()
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if (interactive)
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sigprocmask(SIG_BLOCK, &blocked_set, NULL);
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if (pid == 0 && wnohang) {
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/* We had at least one successful
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* wait() before. We waited
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* with WNOHANG second time.
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* Stop collecting more tracees,
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* process what we already have.
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*/
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break;
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}
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if (pid == -1) {
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switch (wait_errno) {
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case EINTR:
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@ -2330,15 +2336,15 @@ trace()
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*/
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#if 0
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if (nprocs == 0)
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return 0;
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return NULL;
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fprintf(stderr, "strace: proc miscount\n");
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exit(1);
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#endif
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return 0;
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return NULL;
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default:
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errno = wait_errno;
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perror("strace: wait");
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return -1;
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exit(1);
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}
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}
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if (pid == popen_pid) {
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@ -2369,7 +2375,7 @@ trace()
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tcp = alloctcb(pid);
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if (tcp == NULL) {
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kill(pid, SIGKILL); /* XXX */
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return 0;
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return NULL;
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}
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tcp->flags |= TCB_ATTACHED | TCB_SUSPENDED;
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if (!qflag)
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@ -2380,7 +2386,7 @@ Process %d attached (waiting for parent)\n",
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else
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/* This can happen if a clone call used
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CLONE_PTRACE itself. */
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#endif
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#endif /* LINUX */
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{
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fprintf(stderr, "unknown pid: %u\n", pid);
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if (WIFSTOPPED(status))
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@ -2388,14 +2394,36 @@ Process %d attached (waiting for parent)\n",
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exit(1);
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}
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}
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/* set current output file */
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outf = tcp->outf;
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if (cflag) {
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#ifdef LINUX
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tv_sub(&tcp->dtime, &ru.ru_stime, &tcp->stime);
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tcp->stime = ru.ru_stime;
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#endif /* !LINUX */
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#endif
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}
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tcp->wait_status = status;
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#ifdef LINUX
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tcp->next_need_service = found_tcps;
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found_tcps = tcp;
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wnohang = WNOHANG;
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#endif
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#ifdef SUNOS4
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/* Probably need to replace wait with waitpid
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* and loop on Sun too, but I can't test it. Volunteers?
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*/
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break;
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#endif
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} /* while (1) - collecting all stopped/exited tracees */
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return tcp;
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}
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static int
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handle_stopped_tcbs(struct tcb *tcp)
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{
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for (; tcp; tcp = tcp->next_need_service) {
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int pid;
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int status;
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if (tcp->flags & TCB_SUSPENDED) {
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/*
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@ -2408,6 +2436,11 @@ Process %d attached (waiting for parent)\n",
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*/
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continue;
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}
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outf = tcp->outf;
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status = tcp->wait_status;
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pid = tcp->pid;
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if (WIFSIGNALED(status)) {
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if (pid == strace_child)
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exit_code = 0x100 | WTERMSIG(status);
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@ -2682,6 +2715,37 @@ Process %d attached (waiting for parent)\n",
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cleanup();
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return -1;
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}
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} /* for each tcp */
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return 0;
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}
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static int
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trace()
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{
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int rc;
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struct tcb *tcbs;
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while (nprocs != 0) {
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if (interrupted)
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return 0;
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if (interactive)
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sigprocmask(SIG_SETMASK, &empty_set, NULL);
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/* The loop of "wait for one tracee, serve it, repeat"
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* may leave some tracees never served.
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* Kernel provides no guarantees of fairness when you have
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* many waitable tasks.
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* Try strace -f with test/many_looping_threads.c example.
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* To fix it, we collect *all* waitable tasks, then handle
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* them all, then repeat.
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*/
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tcbs = collect_stopped_tcbs();
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if (!tcbs)
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break;
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rc = handle_stopped_tcbs(tcbs);
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if (rc)
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return rc;
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}
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return 0;
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}
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37
test/many_looping_threads.c
Normal file
37
test/many_looping_threads.c
Normal file
@ -0,0 +1,37 @@
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/* This test is not yet added to Makefile */
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#include <stdio.h>
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#include <pthread.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <signal.h>
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#include <stdlib.h>
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static int thd_no;
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static void *sub_thd(void *c)
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{
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fprintf(stderr, "sub-thread %d created\n", ++thd_no);
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for (;;)
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getuid();
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return NULL;
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}
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int main(int argc, char **argv)
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{
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int i;
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pthread_t *thd;
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int num_threads = 1;
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if (argv[1])
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num_threads = atoi(argv[1]);
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thd = malloc(num_threads * sizeof(thd[0]));
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fprintf(stderr, "test start, num_threads:%d...\n", num_threads);
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for (i = 0; i < num_threads; i++) {
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pthread_create(&thd[i], NULL, sub_thd, NULL);
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fprintf(stderr, "after pthread_create\n");
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}
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/* Exit. This kills all threads */
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return 0;
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}
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