xargs: optional support for -P NUM. Closes 9511

Based on patch by Johannes Schindelin <johannes.schindelin@gmx.de>

function                                             old     new   delta
xargs_exec                                             -     294    +294
packed_usage                                       31757   31772     +15
xargs_main                                           787     719     -68
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/1 up/down: 309/-68)           Total: 241 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2017-08-24 13:23:54 +02:00
parent b270be3fb3
commit 14551b7036

View File

@ -59,6 +59,11 @@
//config: depends on XARGS
//config: help
//config: Support -I STR and -i[STR] options.
//config:
//config:config FEATURE_XARGS_SUPPORT_PARALLEL
//config: bool "Enable -P N: processes to run in parallel"
//config: default y
//config: depends on XARGS
//applet:IF_XARGS(APPLET_NOEXEC(xargs, xargs, BB_DIR_USR_BIN, BB_SUID_DROP, xargs))
@ -99,38 +104,121 @@ struct globals {
#endif
const char *eof_str;
int idx;
#if ENABLE_FEATURE_XARGS_SUPPORT_PARALLEL
int running_procs;
int max_procs;
#endif
smalluint xargs_exitcode;
} FIX_ALIASING;
#define G (*(struct globals*)bb_common_bufsiz1)
#define INIT_G() do { \
setup_common_bufsiz(); \
G.eof_str = NULL; /* need to clear by hand because we are NOEXEC applet */ \
G.idx = 0; \
IF_FEATURE_XARGS_SUPPORT_PARALLEL(G.running_procs = 0;) \
IF_FEATURE_XARGS_SUPPORT_PARALLEL(G.max_procs = 1;) \
G.xargs_exitcode = 0; \
IF_FEATURE_XARGS_SUPPORT_REPL_STR(G.repl_str = "{}";) \
IF_FEATURE_XARGS_SUPPORT_REPL_STR(G.eol_ch = '\n';) \
} while (0)
/*
* Returns 0 if xargs should continue (but may set G.xargs_exitcode to 123).
* Else sets G.xargs_exitcode to error code and returns nonzero.
*
* If G.max_procs == 0, performs final waitpid() loop for all children.
*/
static int xargs_exec(void)
{
int status;
#if !ENABLE_FEATURE_XARGS_SUPPORT_PARALLEL
status = spawn_and_wait(G.args);
#else
if (G.max_procs == 1) {
status = spawn_and_wait(G.args);
} else {
pid_t pid;
int wstat;
again:
if (G.running_procs >= G.max_procs)
pid = safe_waitpid(-1, &wstat, 0);
else
pid = wait_any_nohang(&wstat);
if (pid > 0) {
/* We may have children we don't know about:
* sh -c 'sleep 1 & exec xargs ...'
* Do not make G.running_procs go negative.
*/
if (G.running_procs != 0)
G.running_procs--;
status = WIFSIGNALED(wstat)
? 0x180 + WTERMSIG(wstat)
: WEXITSTATUS(wstat);
if (status > 0 && status < 255) {
/* See below why 123 does not abort */
G.xargs_exitcode = 123;
status = 0;
}
if (status == 0)
goto again; /* maybe we have more children? */
/* else: "bad" status, will bail out */
} else if (G.max_procs != 0) {
/* Not in final waitpid() loop,
* and G.running_procs < G.max_procs: start more procs
*/
status = spawn(G.args);
/* here "status" actually holds pid, or -1 */
if (status > 0) {
G.running_procs++;
status = 0;
}
/* else: status == -1 (failed to fork or exec) */
} else {
/* final waitpid() loop: must be ECHILD "no more children" */
status = 0;
}
}
#endif
/* Manpage:
* """xargs exits with the following status:
* 0 if it succeeds
* 123 if any invocation of the command exited with status 1-125
* 124 if the command exited with status 255
* ("""If any invocation of the command exits with a status of 255,
* xargs will stop immediately without reading any further input.
* An error message is issued on stderr when this happens.""")
* 125 if the command is killed by a signal
* 126 if the command cannot be run
* 127 if the command is not found
* 1 if some other error occurred."""
*/
if (status < 0) {
bb_simple_perror_msg(G.args[0]);
return errno == ENOENT ? 127 : 126;
status = (errno == ENOENT) ? 127 : 126;
}
if (status == 255) {
bb_error_msg("%s: exited with status 255; aborting", G.args[0]);
return 124;
}
if (status >= 0x180) {
else if (status >= 0x180) {
bb_error_msg("'%s' terminated by signal %d",
G.args[0], status - 0x180);
return 125;
status = 125;
}
if (status)
return 123;
return 0;
else if (status != 0) {
if (status == 255) {
bb_error_msg("%s: exited with status 255; aborting", G.args[0]);
return 124;
}
/* "123 if any invocation of the command exited with status 1-125"
* This implies that nonzero exit code is remembered,
* but does not cause xargs to stop: we return 0.
*/
G.xargs_exitcode = 123;
status = 0;
}
if (status != 0)
G.xargs_exitcode = status;
return status;
}
/* In POSIX/C locale isspace is only these chars: "\t\n\v\f\r" and space.
@ -436,6 +524,9 @@ static int xargs_ask_confirmation(void)
//usage: IF_FEATURE_XARGS_SUPPORT_REPL_STR(
//usage: "\n -I STR Replace STR within PROG ARGS with input line"
//usage: )
//usage: IF_FEATURE_XARGS_SUPPORT_PARALLEL(
//usage: "\n -P N Run up to N PROGs in parallel"
//usage: )
//usage: IF_FEATURE_XARGS_SUPPORT_TERMOPT(
//usage: "\n -x Exit if size is exceeded"
//usage: )
@ -473,14 +564,14 @@ enum {
IF_FEATURE_XARGS_SUPPORT_CONFIRMATION("p") \
IF_FEATURE_XARGS_SUPPORT_TERMOPT( "x") \
IF_FEATURE_XARGS_SUPPORT_ZERO_TERM( "0") \
IF_FEATURE_XARGS_SUPPORT_REPL_STR( "I:i::")
IF_FEATURE_XARGS_SUPPORT_REPL_STR( "I:i::") \
IF_FEATURE_XARGS_SUPPORT_PARALLEL( "P:+")
int xargs_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int xargs_main(int argc UNUSED_PARAM, char **argv)
{
int initial_idx;
int i;
int child_error = 0;
char *max_args;
char *max_chars;
char *buf;
@ -500,8 +591,14 @@ int xargs_main(int argc UNUSED_PARAM, char **argv)
"no-run-if-empty\0" No_argument "r",
&max_args, &max_chars, &G.eof_str, &G.eof_str
IF_FEATURE_XARGS_SUPPORT_REPL_STR(, &G.repl_str, &G.repl_str)
IF_FEATURE_XARGS_SUPPORT_PARALLEL(, &G.max_procs)
);
#if ENABLE_FEATURE_XARGS_SUPPORT_PARALLEL
if (G.max_procs <= 0) /* -P0 means "run lots of them" */
G.max_procs = 100; /* let's not go crazy high */
#endif
/* -E ""? You may wonder why not just omit -E?
* This is used for portability:
* old xargs was using "_" as default for -E / -e */
@ -620,11 +717,8 @@ int xargs_main(int argc UNUSED_PARAM, char **argv)
}
if (!(opt & OPT_INTERACTIVE) || xargs_ask_confirmation()) {
child_error = xargs_exec();
}
if (child_error > 0 && child_error != 123) {
break;
if (xargs_exec() != 0)
break; /* G.xargs_exitcode is set by xargs_exec() */
}
overlapping_strcpy(buf, rem);
@ -635,7 +729,12 @@ int xargs_main(int argc UNUSED_PARAM, char **argv)
free(buf);
}
return child_error;
#if ENABLE_FEATURE_XARGS_SUPPORT_PARALLEL
G.max_procs = 0;
xargs_exec(); /* final waitpid() loop */
#endif
return G.xargs_exitcode;
}