14551b703
Denys Vlasenko
2017-08-24
Subject
xargs: optional support for -P NUM. Closes 9511
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findutils/xargs.c+117 -18
| @@ -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; |
| - | } |
| - | if (status == 255) { |
| - | bb_error_msg("%s: exited with status 255; aborting", G.args[0]); |
| - | return 124; |
| + | status = (errno == ENOENT) ? 127 : 126; |
| } | |
| - | 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; |
| } | |