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Merge pull request #1118 from nico/posixspawn2

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Use posix_spawn() instead of fork()/exec().
This commit is contained in:
Nico Weber 2016-04-05 14:13:44 -04:00
commit aea5a4d41f
2 changed files with 49 additions and 47 deletions
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93
src/subprocess-posix.cc
View File

@ -22,6 +22,9 @@
#include <stdio.h>
#include <string.h>
#include <sys/wait.h>
#include <spawn.h>
extern char** environ;
#include "util.h"
@ -50,62 +53,60 @@ bool Subprocess::Start(SubprocessSet* set, const string& command) {
#endif // !USE_PPOLL
SetCloseOnExec(fd_);
pid_ = fork();
if (pid_ < 0)
Fatal("fork: %s", strerror(errno));
posix_spawn_file_actions_t action;
if (posix_spawn_file_actions_init(&action) != 0)
Fatal("posix_spawn_file_actions_init: %s", strerror(errno));
if (pid_ == 0) {
close(output_pipe[0]);
if (posix_spawn_file_actions_addclose(&action, output_pipe[0]) != 0)
Fatal("posix_spawn_file_actions_addclose: %s", strerror(errno));
// Track which fd we use to report errors on.
int error_pipe = output_pipe[1];
do {
if (sigaction(SIGINT, &set->old_int_act_, 0) < 0)
break;
if (sigaction(SIGTERM, &set->old_term_act_, 0) < 0)
break;
if (sigaction(SIGHUP, &set->old_hup_act_, 0) < 0)
break;
if (sigprocmask(SIG_SETMASK, &set->old_mask_, 0) < 0)
break;
posix_spawnattr_t attr;
if (posix_spawnattr_init(&attr) != 0)
Fatal("posix_spawnattr_init: %s", strerror(errno));
if (!use_console_) {
// Put the child in its own process group, so ctrl-c won't reach it.
if (setpgid(0, 0) < 0)
break;
short flags = 0;
// Open /dev/null over stdin.
int devnull = open("/dev/null", O_RDONLY);
if (devnull < 0)
break;
if (dup2(devnull, 0) < 0)
break;
close(devnull);
flags |= POSIX_SPAWN_SETSIGMASK;
if (posix_spawnattr_setsigmask(&attr, &set->old_mask_) != 0)
Fatal("posix_spawnattr_setsigmask: %s", strerror(errno));
// Signals which are set to be caught in the calling process image are set to
// default action in the new process image, so no explicit
// POSIX_SPAWN_SETSIGDEF parameter is needed.
if (dup2(output_pipe[1], 1) < 0 ||
dup2(output_pipe[1], 2) < 0)
break;
// TODO: Consider using POSIX_SPAWN_USEVFORK on Linux with glibc?
// Now can use stderr for errors.
error_pipe = 2;
close(output_pipe[1]);
}
// In the console case, output_pipe is still inherited by the child and
// closed when the subprocess finishes, which then notifies ninja.
if (!use_console_) {
// Put the child in its own process group, so ctrl-c won't reach it.
flags |= POSIX_SPAWN_SETPGROUP;
// No need to posix_spawnattr_setpgroup(&attr, 0), it's the default.
execl("/bin/sh", "/bin/sh", "-c", command.c_str(), (char *) NULL);
} while (false);
// If we get here, something went wrong; the execl should have
// replaced us.
char* err = strerror(errno);
if (write(error_pipe, err, strlen(err)) < 0) {
// If the write fails, there's nothing we can do.
// But this block seems necessary to silence the warning.
// Open /dev/null over stdin.
if (posix_spawn_file_actions_addopen(&action, 0, "/dev/null", O_RDONLY,
0) != 0) {
Fatal("posix_spawn_file_actions_addopen: %s", strerror(errno));
}
_exit(1);
if (posix_spawn_file_actions_adddup2(&action, output_pipe[1], 1) != 0)
Fatal("posix_spawn_file_actions_adddup2: %s", strerror(errno));
if (posix_spawn_file_actions_adddup2(&action, output_pipe[1], 2) != 0)
Fatal("posix_spawn_file_actions_adddup2: %s", strerror(errno));
// In the console case, output_pipe is still inherited by the child and
// closed when the subprocess finishes, which then notifies ninja.
}
if (posix_spawnattr_setflags(&attr, flags) != 0)
Fatal("posix_spawnattr_setflags: %s", strerror(errno));
const char* spawned_args[] = { "/bin/sh", "-c", command.c_str(), NULL };
if (posix_spawn(&pid_, "/bin/sh", &action, &attr,
const_cast<char**>(spawned_args), environ) != 0)
Fatal("posix_spawn: %s", strerror(errno));
if (posix_spawnattr_destroy(&attr) != 0)
Fatal("posix_spawnattr_destroy: %s", strerror(errno));
if (posix_spawn_file_actions_destroy(&action) != 0)
Fatal("posix_spawn_file_actions_destroy: %s", strerror(errno));
close(output_pipe[1]);
return true;
}

3
src/subprocess_test.cc
View File

@ -226,7 +226,8 @@ TEST_F(SubprocessTest, SetWithLots) {
rlimit rlim;
ASSERT_EQ(0, getrlimit(RLIMIT_NOFILE, &rlim));
if (rlim.rlim_cur < kNumProcs) {
printf("Raise [ulimit -n] well above %u (currently %lu) to make this test go\n", kNumProcs, rlim.rlim_cur);
printf("Raise [ulimit -n] above %u (currently %lu) to make this test go\n",
kNumProcs, rlim.rlim_cur);
return;
}