diff options
| -rw-r--r-- | shell/ash.c | 83 |
1 files changed, 70 insertions, 13 deletions
diff --git a/shell/ash.c b/shell/ash.c index b060d227a..1ef02b8be 100644 --- a/shell/ash.c +++ b/shell/ash.c @@ -295,6 +295,7 @@ struct globals_misc { volatile int suppress_int; /* counter */ volatile /*sig_atomic_t*/ smallint pending_int; /* 1 = got SIGINT */ + volatile /*sig_atomic_t*/ smallint got_sigchld; /* 1 = got SIGCHLD */ /* last pending signal */ volatile /*sig_atomic_t*/ smallint pending_sig; smallint exception_type; /* kind of exception (0..5) */ @@ -370,6 +371,7 @@ extern struct globals_misc *const ash_ptr_to_globals_misc; #define exception_type (G_misc.exception_type ) #define suppress_int (G_misc.suppress_int ) #define pending_int (G_misc.pending_int ) +#define got_sigchld (G_misc.got_sigchld ) #define pending_sig (G_misc.pending_sig ) #define isloginsh (G_misc.isloginsh ) #define nullstr (G_misc.nullstr ) @@ -3388,7 +3390,14 @@ ignoresig(int signo) static void signal_handler(int signo) { + if (signo == SIGCHLD) { + got_sigchld = 1; + if (!trap[SIGCHLD]) + return; + } + gotsig[signo - 1] = 1; + pending_sig = signo; if (signo == SIGINT && !trap[SIGINT]) { if (!suppress_int) { @@ -3396,8 +3405,6 @@ signal_handler(int signo) raise_interrupt(); /* does not return */ } pending_int = 1; - } else { - pending_sig = signo; } } @@ -3455,6 +3462,9 @@ setsignal(int signo) //whereas we have to restore it to what shell got on entry //from the parent. See comment above + if (signo == SIGCHLD) + new_act = S_CATCH; + t = &sigmode[signo - 1]; cur_act = *t; if (cur_act == 0) { @@ -3507,6 +3517,7 @@ setsignal(int signo) /* mode flags for dowait */ #define DOWAIT_NONBLOCK 0 #define DOWAIT_BLOCK 1 +#define DOWAIT_BLOCK_OR_SIG 2 #if JOBS /* pgrp of shell on invocation */ @@ -3928,32 +3939,76 @@ sprint_status48(char *s, int status, int sigonly) } static int +wait_block_or_sig(int *status, int wait_flags) +{ + sigset_t mask; + int pid; + + do { + /* Poll all children for changes in their state */ + got_sigchld = 0; + pid = waitpid(-1, status, wait_flags | WNOHANG); + if (pid != 0) + break; /* Error (e.g. EINTR) or pid */ + + /* No child is ready. Sleep until interesting signal is received */ + sigfillset(&mask); + sigprocmask(SIG_SETMASK, &mask, &mask); + while (!got_sigchld && !pending_sig) + sigsuspend(&mask); + sigprocmask(SIG_SETMASK, &mask, NULL); + + /* If it was SIGCHLD, poll children again */ + } while (got_sigchld); + + return pid; +} + + +static int dowait(int block, struct job *job) { int wait_flags; int pid; int status; struct job *jp; - struct job *thisjob; + struct job *thisjob = NULL; TRACE(("dowait(0x%x) called\n", block)); - /* Do a wait system call. If job control is compiled in, we accept - * stopped processes. - * NB: _not_ safe_waitpid, we need to detect EINTR. - */ wait_flags = 0; if (block == DOWAIT_NONBLOCK) wait_flags = WNOHANG; + /* If job control is compiled in, we accept stopped processes too. */ if (doing_jobctl) wait_flags |= WUNTRACED; - pid = waitpid(-1, &status, wait_flags); + + /* It's wrong to call waitpid() outside of INT_OFF region: + * signal can arrive just after syscall return and handler can + * longjmp away, losing stop/exit notification processing. + * Thus, for "jobs" builtin, and for waiting for a fg job, + * we call waitpid() (blocking or non-blocking) inside INT_OFF. + * + * However, for "wait" builtin it is wrong to simply call waitpid() + * in INT_OFF region: "wait" needs to wait for any running job + * to change state, but should exit on any trap too. + * In INT_OFF region, a signal just before syscall entry can set + * pending_sig valiables, but we can't check them, and we would + * either enter a sleeping waitpid() (BUG), or need to busy-loop. + * Because of this, we run inside INT_OFF, but use a special routine + * which combines waitpid() and sigsuspend(). + */ + INT_OFF; + if (block == DOWAIT_BLOCK_OR_SIG) + pid = wait_block_or_sig(&status, wait_flags); + else + /* NB: _not_ safe_waitpid, we need to detect EINTR. */ + pid = waitpid(-1, &status, wait_flags); TRACE(("wait returns pid=%d, status=0x%x, errno=%d(%s)\n", pid, status, errno, strerror(errno))); if (pid <= 0) - return pid; + goto out; - INT_OFF; thisjob = NULL; for (jp = curjob; jp; jp = jp->prev_job) { int jobstate; @@ -4217,7 +4272,7 @@ waitcmd(int argc UNUSED_PARAM, char **argv) * with an exit status greater than 128, immediately after which * the trap is executed." */ - dowait(DOWAIT_BLOCK, NULL); ///DOWAIT_WAITCMD + dowait(DOWAIT_BLOCK_OR_SIG, NULL); /* if child sends us a signal *and immediately exits*, * dowait() returns pid > 0. Check this case, * not "if (dowait() < 0)"! @@ -4244,7 +4299,7 @@ waitcmd(int argc UNUSED_PARAM, char **argv) } /* loop until process terminated or stopped */ while (job->state == JOBRUNNING) { - dowait(DOWAIT_BLOCK, NULL); ///DOWAIT_WAITCMD + dowait(DOWAIT_BLOCK_OR_SIG, NULL); if (pending_sig) goto sigout; } @@ -13113,7 +13168,9 @@ init(void) /* we will never free this */ basepf.next_to_pgetc = basepf.buf = ckmalloc(IBUFSIZ); - signal(SIGCHLD, SIG_DFL); + sigmode[SIGCHLD - 1] = S_DFL; + setsignal(SIGCHLD); + /* bash re-enables SIGHUP which is SIG_IGNed on entry. * Try: "trap '' HUP; bash; echo RET" and type "kill -HUP $$" */ |