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ash: use pause(), not sigsuspend(), in wait builtin

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Same effect, smaller code

function                                             old     new   delta
dowait                                               463     374     -89

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2016-10-28 17:16:11 +02:00
parent d81e9f5093
commit 8f7b0248ad
1 changed files with 31 additions and 26 deletions
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57
shell/ash.c
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@ -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)