Enable SIGINT to srun with pending job step

The logic added to wake pending job steps as soon as resources become
available lacked signal handling logic. This adds signal handling logic.
Fix for bug 339

src/api/step_ctx.c

@@ -64,10 +64,24 @@
 #include "src/common/slurm_protocol_api.h"
 #include "src/common/slurm_protocol_defs.h"
 #include "src/common/xmalloc.h"
+#include "src/common/xsignal.h"
 #include "src/common/xstring.h"
-#include "src/common/slurm_cred.h"
 #include "src/api/step_ctx.h"
 
+int step_signals[] = {
+	SIGINT,  SIGQUIT, SIGCONT, SIGTERM, SIGHUP,
+	SIGALRM, SIGUSR1, SIGUSR2, SIGPIPE, 0 };
+static int destroy_step = 0;
+
+static void _signal_while_allocating(int signo)
+{
+	debug("Got signal %d", signo);
+	if (signo == SIGCONT)
+		return;
+
+	destroy_step = 1;
+}
+
 static void
 _job_fake_cred(struct slurm_step_ctx_struct *ctx)
 {
@@ -203,7 +217,7 @@ slurm_step_ctx_create_timeout (const slurm_step_ctx_params_t *step_params,
 	struct slurm_step_ctx_struct *ctx = NULL;
 	job_step_create_request_msg_t *step_req = NULL;
 	job_step_create_response_msg_t *step_resp = NULL;
-	int rc, time_left = timeout;
+	int i, rc, time_left = timeout;
 	int sock = -1;
 	short port = 0;
 	int errnum = 0;
@@ -232,12 +246,22 @@ slurm_step_ctx_create_timeout (const slurm_step_ctx_params_t *step_params,
 		struct pollfd fds;
 		fds.fd = sock;
 		fds.events = POLLIN;
+		xsignal_unblock(step_signals);
+		for (i = 0; step_signals[i]; i++)
+			xsignal(step_signals[i], _signal_while_allocating);
 		while ((rc = poll(&fds, 1, time_left)) <= 0) {
+			if (destroy_step)
+				break;
 			if ((errno == EINTR) || (errno == EAGAIN))
 				continue;
 			break;
 		}
-		rc = slurm_job_step_create(step_req, &step_resp);
+		xsignal_block(step_signals);
+		if (destroy_step) {
+			info("Cancelled pending job step");
+			errno = ESLURM_ALREADY_DONE;
+		} else
+			rc = slurm_job_step_create(step_req, &step_resp);
 	}
 
 	if ((rc < 0) || (step_resp == NULL)) {