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hush: make read builtin interruptible.

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function                                             old     new   delta
builtin_read                                         185     471    +286
check_and_run_traps                                  200     262     +62
nonblock_immune_read                                  73     119     +46
sigismember                                            -      44     +44
record_signal                                          -      21     +21
sigisemptyset                                          -      16     +16
...
------------------------------------------------------------------------------
(add/remove: 5/0 grow/shrink: 7/5 up/down: 483/-46)           Total: 437 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2011-05-08 21:23:43 +02:00
parent 80c5b6893d
commit 80542bad2f
5 changed files with 120 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/libbb.h
View File

@ -672,7 +672,7 @@ void* xrealloc_vector_helper(void *vector, unsigned sizeof_and_shift, int idx) F
extern ssize_t safe_read(int fd, void *buf, size_t count) FAST_FUNC;
extern ssize_t nonblock_immune_read(int fd, void *buf, size_t count) FAST_FUNC;
extern ssize_t nonblock_immune_read(int fd, void *buf, size_t count, int loop_on_EINTR) FAST_FUNC;
// NB: will return short read on error, not -1,
// if some data was read before error occurred
extern ssize_t full_read(int fd, void *buf, size_t count) FAST_FUNC;

9
libbb/read_printf.c
View File

@ -55,19 +55,20 @@
* which detects EAGAIN and uses poll() to wait on the fd.
* Thankfully, poll() doesn't care about O_NONBLOCK flag.
*/
ssize_t FAST_FUNC nonblock_immune_read(int fd, void *buf, size_t count)
ssize_t FAST_FUNC nonblock_immune_read(int fd, void *buf, size_t count, int loop_on_EINTR)
{
struct pollfd pfd[1];
ssize_t n;
while (1) {
n = safe_read(fd, buf, count);
n = loop_on_EINTR ? safe_read(fd, buf, count) : read(fd, buf, count);
if (n >= 0 || errno != EAGAIN)
return n;
/* fd is in O_NONBLOCK mode. Wait using poll and repeat */
pfd[0].fd = fd;
pfd[0].events = POLLIN;
safe_poll(pfd, 1, -1); /* note: this pulls in printf */
/* note: safe_poll pulls in printf */
loop_on_EINTR ? safe_poll(pfd, 1, -1) : poll(pfd, 1, -1);
}
}
@ -90,7 +91,7 @@ char* FAST_FUNC xmalloc_reads(int fd, size_t *maxsz_p)
p = buf + sz;
sz += 128;
}
if (nonblock_immune_read(fd, p, 1) != 1) {
if (nonblock_immune_read(fd, p, 1, /*loop_on_EINTR:*/ 1) != 1) {
/* EOF/error */
if (p == buf) { /* we read nothing */
free(buf);

6
shell/ash.c
View File

@ -5918,7 +5918,7 @@ expbackq(union node *cmd, int quoted, int quotes)
read:
if (in.fd < 0)
break;
i = nonblock_immune_read(in.fd, buf, sizeof(buf));
i = nonblock_immune_read(in.fd, buf, sizeof(buf), /*loop_on_EINTR:*/ 1);
TRACE(("expbackq: read returns %d\n", i));
if (i <= 0)
break;
@ -9617,7 +9617,7 @@ preadfd(void)
#if ENABLE_FEATURE_EDITING
retry:
if (!iflag || g_parsefile->pf_fd != STDIN_FILENO)
nr = nonblock_immune_read(g_parsefile->pf_fd, buf, IBUFSIZ - 1);
nr = nonblock_immune_read(g_parsefile->pf_fd, buf, IBUFSIZ - 1, /*loop_on_EINTR:*/ 1);
else {
int timeout = -1;
# if ENABLE_ASH_IDLE_TIMEOUT
@ -9663,7 +9663,7 @@ preadfd(void)
}
}
#else
nr = nonblock_immune_read(g_parsefile->pf_fd, buf, IBUFSIZ - 1);
nr = nonblock_immune_read(g_parsefile->pf_fd, buf, IBUFSIZ - 1, /*loop_on_EINTR:*/ 1);
#endif
#if 0 /* disabled: nonblock_immune_read() handles this problem */

98
shell/hush.c
View File

@ -795,8 +795,15 @@ struct globals {
/* which signals have non-DFL handler (even with no traps set)? */
unsigned non_DFL_mask;
char **traps; /* char *traps[NSIG] */
sigset_t blocked_set;
/* Signal mask on the entry to the (top-level) shell. Never modified. */
sigset_t inherited_set;
/* Starts equal to inherited_set,
* but shell-special signals are added and SIGCHLD is removed.
* When a trap is set/cleared, signal is added to/removed from it:
*/
sigset_t blocked_set;
/* Used by read() */
sigset_t detected_set;
#if HUSH_DEBUG
unsigned long memleak_value;
int debug_indent;
@ -1476,6 +1483,17 @@ static int check_and_run_traps(int sig)
goto got_sig;
while (1) {
if (!sigisemptyset(&G.detected_set)) {
sig = 0;
do {
sig++;
if (sigismember(&G.detected_set, sig)) {
sigdelset(&G.detected_set, sig);
goto got_sig;
}
} while (sig < NSIG);
}
sig = sigtimedwait(&G.blocked_set, NULL, &zero_timespec);
if (sig <= 0)
break;
@ -8484,6 +8502,32 @@ static int FAST_FUNC builtin_pwd(char **argv UNUSED_PARAM)
return EXIT_SUCCESS;
}
/* Interruptibility of read builtin in bash
* (tested on bash-4.2.8 by sending signals (not by ^C)):
*
* Empty trap makes read ignore corresponding signal, for any signal.
*
* SIGINT:
* - terminates non-interactive shell;
* - interrupts read in interactive shell;
* if it has non-empty trap:
* - executes trap and returns to command prompt in interactive shell;
* - executes trap and returns to read in non-interactive shell;
* SIGTERM:
* - is ignored (does not interrupt) read in interactive shell;
* - terminates non-interactive shell;
* if it has non-empty trap:
* - executes trap and returns to read;
* SIGHUP:
* - terminates shell (regardless of interactivity);
* if it has non-empty trap:
* - executes trap and returns to read;
*/
/* helper */
static void record_signal(int sig)
{
sigaddset(&G.detected_set, sig);
}
static int FAST_FUNC builtin_read(char **argv)
{
const char *r;
@ -8491,7 +8535,9 @@ static int FAST_FUNC builtin_read(char **argv)
char *opt_p = NULL;
char *opt_t = NULL;
char *opt_u = NULL;
const char *ifs;
int read_flags;
sigset_t saved_blkd_set;
/* "!": do not abort on errors.
* Option string must start with "sr" to match BUILTIN_READ_xxx
@ -8500,10 +8546,47 @@ static int FAST_FUNC builtin_read(char **argv)
if (read_flags == (uint32_t)-1)
return EXIT_FAILURE;
argv += optind;
ifs = get_local_var_value("IFS"); /* can be NULL */
again:
/* We need to temporarily unblock and record signals around read */
saved_blkd_set = G.blocked_set;
{
unsigned sig;
struct sigaction sa, old_sa;
memset(&sa, 0, sizeof(sa));
sigfillset(&sa.sa_mask);
/*sa.sa_flags = 0;*/
sa.sa_handler = record_signal;
sig = 0;
do {
sig++;
if (sigismember(&G.blocked_set, sig)) {
char *sig_trap = (G.traps && G.traps[sig]) ? G.traps[sig] : NULL;
/* If has a nonempty trap... */
if ((sig_trap && sig_trap[0])
/* ...or has no trap and is SIGINT or SIGHUP */
|| (!sig_trap && (sig == SIGINT || sig == SIGHUP))
) {
sigaction(sig, &sa, &old_sa);
if (old_sa.sa_handler == SIG_IGN) /* oops... restore back to IGN! */
sigaction_set(sig, &old_sa);
else
sigdelset(&G.blocked_set, sig);
}
}
} while (sig < NSIG-1);
}
if (memcmp(&saved_blkd_set, &G.blocked_set, sizeof(saved_blkd_set)) != 0)
sigprocmask_set(&G.blocked_set);
r = shell_builtin_read(set_local_var_from_halves,
argv,
get_local_var_value("IFS"), /* can be NULL */
ifs,
read_flags,
opt_n,
opt_p,
@ -8511,6 +8594,17 @@ static int FAST_FUNC builtin_read(char **argv)
opt_u
);
if (memcmp(&saved_blkd_set, &G.blocked_set, sizeof(saved_blkd_set)) != 0) {
G.blocked_set = saved_blkd_set;
sigprocmask_set(&G.blocked_set);
}
if ((uintptr_t)r == 1 && errno == EINTR) {
unsigned sig = check_and_run_traps(0);
if (sig && sig != SIGINT)
goto again;
}
if ((uintptr_t)r > 1) {
bb_error_msg("%s", r);
r = (char*)(uintptr_t)1;

17
shell/shell_common.c
View File

@ -36,6 +36,10 @@ int FAST_FUNC is_well_formed_var_name(const char *s, char terminator)
/* read builtin */
/* Needs to be interruptible: shell mush handle traps and shell-special signals
* while inside read. To implement this, be sure to not loop on EINTR
* and return errno == EINTR reliably.
*/
//TODO: use more efficient setvar() which takes a pointer to malloced "VAR=VAL"
//string. hush naturally has it, and ash has setvareq().
//Here we can simply store "VAR=" at buffer start and store read data directly
@ -51,6 +55,7 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
const char *opt_u
)
{
unsigned err;
unsigned end_ms; /* -t TIMEOUT */
int fd; /* -u FD */
int nchars; /* -n NUM */
@ -62,6 +67,8 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
int startword;
smallint backslash;
errno = err = 0;
pp = argv;
while (*pp) {
if (!is_well_formed_var_name(*pp, '\0')) {
@ -153,6 +160,8 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
do {
char c;
errno = 0;
if (end_ms) {
int timeout;
struct pollfd pfd[1];
@ -161,8 +170,9 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
pfd[0].events = POLLIN;
timeout = end_ms - (unsigned)monotonic_ms();
if (timeout <= 0 /* already late? */
|| safe_poll(pfd, 1, timeout) != 1 /* no? wait... */
|| poll(pfd, 1, timeout) != 1 /* no? wait... */
) { /* timed out! */
err = errno;
retval = (const char *)(uintptr_t)1;
goto ret;
}
@ -170,7 +180,8 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
if ((bufpos & 0xff) == 0)
buffer = xrealloc(buffer, bufpos + 0x100);
if (nonblock_immune_read(fd, &buffer[bufpos], 1) != 1) {
if (nonblock_immune_read(fd, &buffer[bufpos], 1, /*loop_on_EINTR:*/ 0) != 1) {
err = errno;
retval = (const char *)(uintptr_t)1;
break;
}
@ -240,6 +251,8 @@ shell_builtin_read(void FAST_FUNC (*setvar)(const char *name, const char *val),
free(buffer);
if (read_flags & BUILTIN_READ_SILENT)
tcsetattr(fd, TCSANOW, &old_tty);
errno = err;
return retval;
}