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-rw-r--r--shell/ash.c83
1 files changed, 70 insertions, 13 deletions
diff --git a/shell/ash.c b/shell/ash.c
index b060d22..1ef02b8 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 $$"
*/