ccanlint: infrastructure to run commands async.

We use the lbalance module to figure out how many to run in parallel.

tools/ccanlint/Makefile

@@ -9,6 +9,7 @@ CORE_OBJS := \
 	ccan/grab_file/grab_file.o \
 	ccan/hash/hash.o \
 	ccan/htable/htable.o \
+	ccan/lbalance/lbalance.o \
 	ccan/noerr/noerr.o \
 	ccan/opt/helpers.o \
 	ccan/opt/opt.o \
@@ -20,6 +21,7 @@ CORE_OBJS := \
 	ccan/talloc/talloc.o \
 	ccan/talloc_link/talloc_link.o \
 	ccan/time/time.o \
+	tools/ccanlint/async.o \
 	tools/ccanlint/ccanlint.o \
 	tools/ccanlint/file_analysis.o \
 	tools/ccanlint/licenses.o \

tools/ccanlint/async.c

@@ -0,0 +1,200 @@
+#include "ccanlint.h"
+#include "../tools.h"
+#include <sys/types.h>
+#include <sys/time.h>
+#include <sys/resource.h>
+#include <sys/wait.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <err.h>
+#include <assert.h>
+#include <ccan/lbalance/lbalance.h>
+#include <ccan/tlist/tlist.h>
+#include <ccan/grab_file/grab_file.h>
+#include <ccan/time/time.h>
+#include <ccan/talloc/talloc.h>
+
+static struct lbalance *lb;
+TLIST_TYPE(command, struct command);
+static struct tlist_command pending = TLIST_INIT(pending);
+static struct tlist_command running = TLIST_INIT(running);
+static unsigned int num_running = 0;
+static struct tlist_command done = TLIST_INIT(done);
+
+struct command {
+	struct list_node list;
+	char *command;
+	pid_t pid;
+	int output_fd;
+	unsigned int time_ms;
+	struct lbalance_task *task;
+	int status;
+	char *output;
+	bool done;
+	const void *ctx;
+};
+
+static void killme(int sig)
+{
+	kill(-getpid(), SIGKILL);
+}
+
+static void run_more(void)
+{
+	struct command *c;
+
+	while (num_running < lbalance_target(lb)) {
+		int p[2];
+		c = tlist_top(&pending, struct command, list);
+		if (!c)
+			break;
+
+		if (pipe(p) != 0)
+			err(1, "Pipe failed");
+		c->pid = fork();
+		if (c->pid == -1)
+			err(1, "Fork failed");
+		if (c->pid == 0) {
+			struct itimerval itim;
+
+			if (dup2(p[1], STDOUT_FILENO) != STDOUT_FILENO
+			    || dup2(p[1], STDERR_FILENO) != STDERR_FILENO
+			    || close(p[0]) != 0
+			    || close(STDIN_FILENO) != 0
+			    || open("/dev/null", O_RDONLY) != STDIN_FILENO)
+				exit(128);
+
+			signal(SIGALRM, killme);
+			itim.it_interval.tv_sec = itim.it_interval.tv_usec = 0;
+			itim.it_value = time_from_msec(c->time_ms);
+			setitimer(ITIMER_REAL, &itim, NULL);
+
+			c->status = system(c->command);
+			if (WIFEXITED(c->status))
+				exit(WEXITSTATUS(c->status));
+			/* Here's a hint... */
+			exit(128 + WTERMSIG(c->status));
+		}
+
+		if (tools_verbose)
+			printf("Running async: %s => %i\n", c->command, c->pid);
+
+		close(p[1]);
+		c->output_fd = p[0];
+		c->task = lbalance_task_new(lb);
+		tlist_del_from(&pending, c, list);
+		tlist_add_tail(&running, c, list);
+		num_running++;
+	}
+}
+
+static int destroy_command(struct command *command)
+{
+	if (!command->done && command->pid) {
+		kill(-command->pid, SIGKILL);
+		close(command->output_fd);
+		num_running--;
+	}
+
+	tlist_del(command, list);
+	return 0;
+}
+
+void run_command_async(const void *ctx, unsigned int time_ms,
+		       const char *fmt, ...)
+{
+	struct command *command;
+	va_list ap;
+
+	assert(ctx);
+
+	if (!lb)
+		lb = lbalance_new();
+
+	command = talloc(ctx, struct command);
+	command->ctx = ctx;
+	command->time_ms = time_ms;
+	command->pid = 0;
+	command->output = talloc_strdup(command, "");
+	va_start(ap, fmt);
+	command->command = talloc_vasprintf(command, fmt, ap);
+	va_end(ap);
+	tlist_add_tail(&pending, command, list);
+	command->done = false;
+	talloc_set_destructor(command, destroy_command);
+
+	run_more();
+}
+
+static void reap_output(void)
+{
+	fd_set in;
+	struct command *c, *next;
+	int max_fd = 0;
+
+	FD_ZERO(&in);
+
+	tlist_for_each(&running, c, list) {
+		FD_SET(c->output_fd, &in);
+		if (c->output_fd > max_fd)
+			max_fd = c->output_fd;
+	}
+
+	if (select(max_fd+1, &in, NULL, NULL, NULL) < 0)
+		err(1, "select failed");
+
+	tlist_for_each_safe(&running, c, next, list) {
+		if (FD_ISSET(c->output_fd, &in)) {
+			int old_len, len;
+			old_len = talloc_array_length(c->output);
+			c->output = talloc_realloc(c, c->output, char,
+						   old_len + 1024);
+			len = read(c->output_fd, c->output + old_len, 1024);
+			if (len < 0)
+				err(1, "Reading from async command");
+			c->output = talloc_realloc(c, c->output, char,
+						   old_len + len);
+			if (len == 0) {
+				struct rusage ru;
+				wait4(c->pid, &c->status, 0, &ru);
+				if (tools_verbose)
+					printf("Finished async %i: %s %u\n",
+					       c->pid,
+					       WIFEXITED(c->status)
+					       ? "exit status"
+					       : "killed by signal",
+					       WIFEXITED(c->status)
+					       ? WEXITSTATUS(c->status)
+					       : WTERMSIG(c->status));
+				lbalance_task_free(c->task, &ru);
+				c->task = NULL;
+				c->done = true;
+				close(c->output_fd);
+				tlist_del_from(&running, c, list);
+				tlist_add_tail(&done, c, list);
+				num_running--;
+			}
+		}
+	}
+}
+
+void *collect_command(bool *ok, char **output)
+{
+	struct command *c;
+	const void *ctx;
+
+	while ((c = tlist_top(&done, struct command, list)) == NULL) {
+		if (tlist_empty(&pending) && tlist_empty(&running))
+			return NULL;
+		reap_output();
+		run_more();
+	}
+
+	*ok = (WIFEXITED(c->status) && WEXITSTATUS(c->status) == 0);
+	ctx = c->ctx;
+	*output = talloc_steal(ctx, c->output);
+	talloc_free(c);
+	return (void *)ctx;
+}

tools/ccanlint/ccanlint.h

@@ -235,6 +235,13 @@ char **per_file_options(const struct ccanlint *test, struct ccan_file *f);
 void score_file_error(struct score *, struct ccan_file *f, unsigned line,
 		      const char *errorfmt, ...);
 
+/* Start a command in the background. */
+void run_command_async(const void *ctx, unsigned int time_ms,
+		       const char *fmt, ...);
+
+/* Get results of a command, returning ctx (and free it). */
+void *collect_command(bool *ok, char **output);
+
 /* Normal tests. */
 extern struct ccanlint trailing_whitespace;