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authorDenys Vlasenko <vda.linux@googlemail.com>2016-10-28 17:16:11 +0200
committerDenys Vlasenko <vda.linux@googlemail.com>2016-10-28 17:16:11 +0200
commit8f7b0248adca9a88351fd7f3dd208775242f3fe6 (patch)
tree813260e706183bee2bd28902587c4e1a7090a615
parentd81e9f5093b222369d510d0b1c0587a411e4c83e (diff)
downloadbusybox-8f7b0248adca9a88351fd7f3dd208775242f3fe6.tar.gz
ash: use pause(), not sigsuspend(), in wait builtin
Same effect, smaller code function old new delta dowait 463 374 -89 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--shell/ash.c57
1 files changed, 31 insertions, 26 deletions
diff --git a/shell/ash.c b/shell/ash.c
index fe112453c..fc1b5d927 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -296,8 +296,7 @@ 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;
+ volatile /*sig_atomic_t*/ smallint pending_sig; /* last pending signal */
smallint exception_type; /* kind of exception (0..5) */
/* exceptions */
#define EXINT 0 /* SIGINT received */
@@ -3515,11 +3514,6 @@ setsignal(int signo)
#define CUR_RUNNING 1
#define CUR_STOPPED 0
-/* 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 */
static int initialpgrp; //references:2
@@ -3940,24 +3934,30 @@ sprint_status48(char *s, int status, int sigonly)
}
static int
-wait_block_or_sig(int *status, int wait_flags)
+wait_block_or_sig(int *status)
{
- 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 job control is active, accept stopped processes too */
+ pid = waitpid(-1, status, doing_jobctl ? (WNOHANG|WUNTRACED) : WNOHANG);
if (pid != 0)
- break; /* Error (e.g. EINTR) or pid */
+ break; /* Error (e.g. EINTR, ECHILD) or pid */
- /* No child is ready. Sleep until interesting signal is received */
+ /* Children exist, but none are ready. Sleep until interesting signal */
+#if 0 /* dash does this */
+ sigset_t mask;
sigfillset(&mask);
sigprocmask(SIG_SETMASK, &mask, &mask);
while (!got_sigchld && !pending_sig)
sigsuspend(&mask);
sigprocmask(SIG_SETMASK, &mask, NULL);
+#else
+ while (!got_sigchld && !pending_sig)
+ pause();
+#endif
/* If it was SIGCHLD, poll children again */
} while (got_sigchld);
@@ -3965,11 +3965,13 @@ wait_block_or_sig(int *status, int wait_flags)
return pid;
}
+#define DOWAIT_NONBLOCK 0
+#define DOWAIT_BLOCK 1
+#define DOWAIT_BLOCK_OR_SIG 2
static int
dowait(int block, struct job *job)
{
- int wait_flags;
int pid;
int status;
struct job *jp;
@@ -3977,13 +3979,6 @@ dowait(int block, struct job *job)
TRACE(("dowait(0x%x) called\n", block));
- 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;
-
/* 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.
@@ -3994,17 +3989,27 @@ dowait(int block, struct job *job)
* 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
+ * pending_sig variables, 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().
+ * which combines waitpid() and pause().
+ * This is the reason why we need to have a handler for SIGCHLD:
+ * SIG_DFL handler does not wake pause().
*/
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. */
+ if (block == DOWAIT_BLOCK_OR_SIG) {
+ pid = wait_block_or_sig(&status);
+ } else {
+ int wait_flags = 0;
+ if (block == DOWAIT_NONBLOCK)
+ wait_flags = WNOHANG;
+ /* if job control is active, accept stopped processes too */
+ if (doing_jobctl)
+ wait_flags |= WUNTRACED;
+ /* 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)