diff options
| -rw-r--r-- | shell/ash.c | 66 |
1 files changed, 20 insertions, 46 deletions
diff --git a/shell/ash.c b/shell/ash.c index 81ac563..92aa5ec 100644 --- a/shell/ash.c +++ b/shell/ash.c @@ -3762,48 +3762,6 @@ sprint_status(char *s, int status, int sigonly) return col; } -/* - * Do a wait system call. If job control is compiled in, we accept - * stopped processes. If block is zero, we return a value of zero - * rather than blocking. - * - * System V doesn't have a non-blocking wait system call. It does - * have a SIGCLD signal that is sent to a process when one of it's - * children dies. The obvious way to use SIGCLD would be to install - * a handler for SIGCLD which simply bumped a counter when a SIGCLD - * was received, and have waitproc bump another counter when it got - * the status of a process. Waitproc would then know that a wait - * system call would not block if the two counters were different. - * This approach doesn't work because if a process has children that - * have not been waited for, System V will send it a SIGCLD when it - * installs a signal handler for SIGCLD. What this means is that when - * a child exits, the shell will be sent SIGCLD signals continuously - * until is runs out of stack space, unless it does a wait call before - * restoring the signal handler. The code below takes advantage of - * this (mis)feature by installing a signal handler for SIGCLD and - * then checking to see whether it was called. If there are any - * children to be waited for, it will be. - * - * If neither SYSV nor BSD is defined, we don't implement nonblocking - * waits at all. In this case, the user will not be informed when - * a background process until the next time she runs a real program - * (as opposed to running a builtin command or just typing return), - * and the jobs command may give out of date information. - */ -static int -waitproc(int wait_flags, int *status) -{ -#if JOBS - if (doing_jobctl) - wait_flags |= WUNTRACED; -#endif - /* NB: _not_ safe_waitpid, we need to detect EINTR */ - return waitpid(-1, status, wait_flags); -} - -/* - * Wait for a process to terminate. - */ static int dowait(int wait_flags, struct job *job) { @@ -3813,9 +3771,15 @@ dowait(int wait_flags, struct job *job) struct job *thisjob; int state; - TRACE(("dowait(%d) called\n", wait_flags)); - pid = waitproc(wait_flags, &status); - TRACE(("wait returns pid=%d, status=%d\n", pid, status)); + TRACE(("dowait(0x%x) called\n", wait_flags)); + + /* Do a wait system call. If job control is compiled in, we accept + * stopped processes. wait_flags may have WNOHANG, preventing blocking. + * NB: _not_ safe_waitpid, we need to detect EINTR */ + pid = waitpid(-1, &status, + (doing_jobctl ? (wait_flags | WUNTRACED) : wait_flags)); + TRACE(("wait returns pid=%d, status=0x%x\n", pid, status)); + if (pid <= 0) { /* If we were doing blocking wait and (probably) got EINTR, * check for pending sigs received while waiting. @@ -8923,7 +8887,10 @@ evalcommand(union node *cmd, int flags) /* Execute the command. */ switch (cmdentry.cmdtype) { default: + #if ENABLE_FEATURE_SH_NOFORK +/* Hmmm... shouldn't it happen somewhere in forkshell() instead? + * Why "fork off a child process if necessary" doesn't apply to NOFORK? */ { /* find_command() encodes applet_no as (-2 - applet_no) */ int applet_no = (- cmdentry.u.index - 2); @@ -8935,7 +8902,6 @@ evalcommand(union node *cmd, int flags) } } #endif - /* Fork off a child process if necessary. */ if (!(flags & EV_EXIT) || trap[0]) { INT_OFF; @@ -8963,6 +8929,12 @@ evalcommand(union node *cmd, int flags) } listsetvar(list, i); } + /* Tight loop with builtins only: + * "while kill -0 $child; do true; done" + * will never exit even if $child died, unless we do this + * to reap the zombie and make kill detect that it's gone: */ + dowait(DOWAIT_NONBLOCK, NULL); + if (evalbltin(cmdentry.u.cmd, argc, argv)) { int exit_status; int i = exception; @@ -8984,6 +8956,8 @@ evalcommand(union node *cmd, int flags) case CMDFUNCTION: listsetvar(varlist.list, 0); + /* See above for the rationale */ + dowait(DOWAIT_NONBLOCK, NULL); if (evalfun(cmdentry.u.func, argc, argv, flags)) goto raise; break; |