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8d7be232a

Denys Vlasenko

2009-05-25

FAILED Duration: 34s

Subject

hush: fix SIGCHLD counting code, but keep it disabled for now.

Binary

No binary (build failed)

Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

—

Build Log

(log yok)

Commit Diff GitHub →

shell/hush.c +66 -19

shell/hush.c+66 -19

@@ -69,7 +69,7 @@
	#endif


-	/* Debug build knobs */
+	/* Build knobs */
	#define LEAK_HUNTING 0
	#define BUILD_AS_NOMMU 0
	/* Enable/disable sanity checks. Ok to enable in production,
@@ -77,6 +77,13 @@
	* Keeping 1 for now even in released versions.
	*/
	#define HUSH_DEBUG 1
+	/* Slightly bigger (+200 bytes), but faster hush.
+	* So far it only enables a trick with counting SIGCHLDs and forks,
+	* which allows us to do fewer waitpid's.
+	* (we can detect a case where neither forks were done nor SIGCHLDs happened
+	* and therefore waitpid will return the same result as last time)
+	*/
+	#define ENABLE_HUSH_FAST 0


	#if BUILD_AS_NOMMU
@@ -485,8 +492,11 @@ struct globals {
	struct function *top_func;
	#endif
	/* Signal and trap handling */
-	// unsigned count_SIGCHLD;
-	// unsigned handled_SIGCHLD;
+	#if ENABLE_HUSH_FAST
+	unsigned count_SIGCHLD;
+	unsigned handled_SIGCHLD;
+	smallint last_waitpid_was_0;
+	#endif
	/* which signals have non-DFL handler (even with no traps set)? */
	unsigned non_DFL_mask;
	char *traps; / char traps[NSIG] /
@@ -1050,7 +1060,7 @@ static void restore_G_args(save_arg_t sv, char *argv)
	* Restore blocked signal set to one inherited by shell just prior to exec.
	*
	* Note: as a result, we do not use signal handlers much. The only uses
-	* are to count SIGCHLDs [disabled - bug somewhere, + bloat]
+	* are to count SIGCHLDs
	* and to restore tty pgrp on signal-induced exit.
	*/
	enum {
@@ -1067,10 +1077,13 @@ enum {
	#endif
	};

-	//static void SIGCHLD_handler(int sig UNUSED_PARAM)
-	//{
-	// G.count_SIGCHLD++;
-	//}
+	#if ENABLE_HUSH_FAST
+	static void SIGCHLD_handler(int sig UNUSED_PARAM)
+	{
+	G.count_SIGCHLD++;
+	//bb_error_msg("[%d] SIGCHLD_handler: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
+	}
+	#endif

	#if ENABLE_HUSH_JOB

@@ -1158,9 +1171,12 @@ static int check_and_run_traps(int sig)
	}
	/* not a trap: special action */
	switch (sig) {
-	// case SIGCHLD:
-	// G.count_SIGCHLD++;
-	// break;
+	#if ENABLE_HUSH_FAST
+	case SIGCHLD:
+	G.count_SIGCHLD++;
+	//bb_error_msg("[%d] check_and_run_traps: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
+	break;
+	#endif
	case SIGINT:
	/* Builtin was ^C'ed, make it look prettier: */
	bb_putchar('\n');
@@ -2665,6 +2681,10 @@ static void setup_heredoc(struct redir_struct *redir)
	#endif
	}
	/* parent */
+	#if ENABLE_HUSH_FAST
+	G.count_SIGCHLD++;
+	//bb_error_msg("[%d] fork in setup_heredoc: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
+	#endif
	enable_restore_tty_pgrp_on_exit();
	#if !BB_MMU
	free(to_free);
@@ -3273,9 +3293,16 @@ static int checkjobs(struct pipe* fg_pipe)
	debug_printf_jobs("checkjobs %p\n", fg_pipe);

	errno = 0;
-	// if (G.handled_SIGCHLD == G.count_SIGCHLD)
-	// /* avoid doing syscall, nothing there anyway */
-	// return rcode;
+	#if ENABLE_HUSH_FAST
+	if (G.handled_SIGCHLD == G.count_SIGCHLD) {
+	//bb_error_msg("[%d] checkjobs: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d was 0?:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD, G.last_waitpid_was_0);
+	/* avoid doing syscall, nothing there anyway */
+	if (G.last_waitpid_was_0)
+	return 0;
+	errno = ECHILD;
+	return -1;
+	}
+	#endif

	attributes = WUNTRACED;
	if (fg_pipe == NULL)
@@ -3294,13 +3321,20 @@ static int checkjobs(struct pipe* fg_pipe)
	int i;
	int dead;

-	// i = G.count_SIGCHLD;
+	#if ENABLE_HUSH_FAST
+	i = G.count_SIGCHLD;
+	#endif
	childpid = waitpid(-1, &status, attributes);
	if (childpid <= 0) {
	if (childpid && errno != ECHILD)
	bb_perror_msg("waitpid");
-	// else /* Until next SIGCHLD, waitpid's are useless */
-	// G.handled_SIGCHLD = i;
+	#if ENABLE_HUSH_FAST
+	else { /* Until next SIGCHLD, waitpid's are useless */
+	G.last_waitpid_was_0 = (childpid == 0);
+	G.handled_SIGCHLD = i;
+	//bb_error_msg("[%d] checkjobs: waitpid returned <= 0, G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
+	}
+	#endif
	break;
	}
	dead = WIFEXITED(status) \|\| WIFSIGNALED(status);
@@ -3696,6 +3730,10 @@ static int run_pipe(struct pipe *pi)
	}

	/* parent or error */
+	#if ENABLE_HUSH_FAST
+	G.count_SIGCHLD++;
+	//bb_error_msg("[%d] fork in run_pipe: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
+	#endif
	enable_restore_tty_pgrp_on_exit();
	#if !BB_MMU
	/* Clean up after vforked child */
@@ -4861,6 +4899,10 @@ static FILE generate_stream_from_string(const char s)
	}

	/* parent */
+	#if ENABLE_HUSH_FAST
+	G.count_SIGCHLD++;
+	//bb_error_msg("[%d] fork in generate_stream_from_string: G.count_SIGCHLD:%d G.handled_SIGCHLD:%d", getpid(), G.count_SIGCHLD, G.handled_SIGCHLD);
+	#endif
	enable_restore_tty_pgrp_on_exit();
	#if !BB_MMU
	free(to_free);
@@ -5990,9 +6032,14 @@ static void block_signals(int second_time)
	second_time ? NULL : &G.inherited_set);
	/* POSIX allows shell to re-enable SIGCHLD
	* even if it was SIG_IGN on entry */
-	// G.count_SIGCHLD++; /* ensure it is != G.handled_SIGCHLD */
+	#if ENABLE_HUSH_FAST
+	G.count_SIGCHLD++; /* ensure it is != G.handled_SIGCHLD */
+	if (!second_time)
+	signal(SIGCHLD, SIGCHLD_handler);
+	#else
	if (!second_time)
-	signal(SIGCHLD, SIG_DFL); // SIGCHLD_handler);
+	signal(SIGCHLD, SIG_DFL);
+	#endif
	}

	#if ENABLE_HUSH_JOB