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| | /*
* Copyright (C) 2012-2016 all contributors <cmogstored-public@bogomips.org>
* License: GPLv3 or later (see COPYING for details)
*/
/*
* process management for iostat(1)
* Since iostat(1) watches the entire system, we only spawn it once
* regardless of the number of mog_svc objects we have.
*/
#include "cmogstored.h"
static pid_t iostat_pid;
static time_t iostat_last_fail;
static struct mog_iostat *iostat;
static time_t iostat_fail_timeout = 10;
enum mog_exerr {
MOG_EXERR_DUP2 = 3,
MOG_EXERR_SIGPROCMASK = 4,
MOG_EXERR_EXECVE = 5
};
static void iostat_atexit(void)
{
if (iostat_pid > 0)
kill(iostat_pid, SIGTERM);
}
static int iostat_pipe_init(int *fds)
{
if (pipe2(fds, O_CLOEXEC) < 0) {
PRESERVE_ERRNO( syslog(LOG_ERR, "pipe2() failed: %m") );
/*
* don't retry here, MFS can deal with not getting iostat
* data for a while
*/
if (errno == ENFILE || errno == EMFILE)
PRESERVE_ERRNO( (void)mog_fdmap_expire(5) );
return -1;
}
CHECK(int, 0, mog_set_nonblocking(fds[0], true));
/* fds[1] (write end) stays _blocking_ */
return 0;
}
static const char *exec_cmd(const char *cmd)
{
time_t last_fail = time(NULL) - iostat_last_fail;
time_t delay = iostat_fail_timeout - last_fail;
if (delay <= 0)
return xasprintf("exec %s", cmd);
syslog(LOG_DEBUG,
"delaying exec of `%s' for %ds due to previous failure",
cmd, (int)delay);
return xasprintf("sleep %d; exec %s", (int)delay, cmd);
}
static int dup2_retry(int oldfd, int newfd) /* vfork-safe */
{
int rc;
do
rc = dup2(oldfd, newfd);
while (rc < 0 && (errno == EINTR || errno == EBUSY));
return rc;
}
static void execve_iostat(int out_fd, const char *cmd) /* vfork-safe */
{
int i;
union {
char *argv[4];
char const *in[4];
} u;
u.in[0] = "/bin/sh";
u.in[1] = "-c";
u.in[2] = cmd;
u.in[3] = 0;
if (dup2_retry(out_fd, STDOUT_FILENO) < 0)
_exit(MOG_EXERR_DUP2);
if (!mog_cloexec_atomic)
mog_cloexec_from(STDERR_FILENO + 1);
/* ignore errors, not much we can do about missing signals */
for (i = 1; i < NSIG; i++)
(void)signal(i, SIG_DFL);
if (sigprocmask(SIG_SETMASK, &mog_emptyset, NULL) != 0)
_exit(MOG_EXERR_SIGPROCMASK);
execve("/bin/sh", u.argv, environ);
_exit(MOG_EXERR_EXECVE);
}
static pid_t iostat_fork_exec(int out_fd)
{
/* rely on /bin/sh to parse iostat command-line args */
const char *cmd = getenv("MOG_IOSTAT_CMD");
int cs;
if (!cmd)
cmd = "iostat -dx 1 30";
cmd = exec_cmd(cmd);
CHECK(int, 0, pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs));
iostat_pid = mog_fork_for_exec();
if (iostat_pid < 0)
syslog(LOG_ERR, "fork() for iostat failed: %m");
else if (iostat_pid == 0) /* child */
execve_iostat(out_fd, cmd);
/* parent */
CHECK(int, 0, pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, 0));
if (iostat_pid > 0)
mog_process_register(iostat_pid, MOG_PROC_IOSTAT);
mog_close(out_fd);
mog_free(cmd);
return iostat_pid;
}
bool mog_iostat_respawn(int oldstatus)
{
int fds[2];
struct mog_fd *mfd;
if (WIFEXITED(oldstatus)) {
int ex = WEXITSTATUS(oldstatus);
const char *fn = 0;
switch (ex) {
case 0: break;
case MOG_EXERR_DUP2: fn = "dup2"; break;
case MOG_EXERR_SIGPROCMASK: fn = "sigprocmask"; break;
case MOG_EXERR_EXECVE: fn = "execve"; break;
default: fn = "(unknown)";
}
if (fn)
syslog(LOG_ERR, "iostat exited due to %s failure", fn);
/* else syslog(LOG_DEBUG, "iostat done, restarting"); */
} else {
iostat_last_fail = time(NULL);
syslog(LOG_WARNING,
"iostat done (pid=%d, status=%d), will retry in %ds",
(int)iostat_pid, oldstatus, (int)iostat_fail_timeout);
}
iostat_pid = 0;
if (iostat_pipe_init(fds) < 0)
return false; /* EMFILE || ENFILE */
if (iostat_fork_exec(fds[1]) < 0)
return false; /* fork() failure */
assert(fds[0] >= 0 && "invalid FD");
mfd = mog_fd_init(fds[0], MOG_FD_TYPE_IOSTAT);
if (iostat == NULL)
atexit(iostat_atexit);
iostat = &mfd->as.iostat;
iostat->queue = mog_notify_queue;
mog_iostat_init(iostat);
mog_idleq_add(iostat->queue, mfd, MOG_QEV_RD);
return true;
}
|