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Add a failsafe to prevent epoll busy-spin.

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This commit is contained in:
Nicholas J. Kain 2015-05-27 12:23:16 -04:00
parent 6c136c3f85
commit 8273b383ab
1 changed files with 19 additions and 12 deletions
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27
src/ndhc.c
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@ -265,7 +265,8 @@ static void do_ndhc_work(void)
struct dhcpmsg dhcp_packet;
struct epoll_event events[1];
long long nowts;
int timeout;
int timeout = 0;
bool had_event;
cs.epollFd = epoll_create1(0);
if (cs.epollFd < 0)
@ -282,9 +283,9 @@ static void do_ndhc_work(void)
if (client_config.enable_rfkill && cs.rfkillFd != -1)
epoll_add(cs.epollFd, cs.rfkillFd);
start_dhcp_listen(&cs);
timeout = 0;
for (;;) {
had_event = false;
int maxi = epoll_wait(cs.epollFd, events, 1, timeout);
if (maxi < 0) {
if (errno == EINTR)
@ -301,6 +302,7 @@ static void do_ndhc_work(void)
int sev_signal = SIGNAL_NONE;
bool force_fingerprint = false;
for (int i = 0; i < maxi; ++i) {
had_event = true;
int fd = events[i].data.fd;
if (fd == cs.signalFd) {
if (!(events[i].events & EPOLLIN))
@ -391,21 +393,26 @@ static void do_ndhc_work(void)
continue;
}
int prev_timeout = timeout;
arp_wake_ts = arp_get_wake_ts();
if (arp_wake_ts < 0) {
if (cs.dhcp_wake_ts != -1) {
timeout = cs.dhcp_wake_ts - nowts;
if (timeout < 0)
timeout = 0;
} else
if (arp_wake_ts < 0 && cs.dhcp_wake_ts < 0) {
timeout = -1;
continue;
} else if (arp_wake_ts < 0) {
timeout = cs.dhcp_wake_ts - nowts;
} else if (cs.dhcp_wake_ts < 0) {
timeout = arp_wake_ts - nowts;
} else {
// If cs.dhcp_wake_ts is -1 then we want to sleep anyway.
timeout = (arp_wake_ts < cs.dhcp_wake_ts ?
arp_wake_ts : cs.dhcp_wake_ts) - nowts;
}
if (timeout < 0)
timeout = 0;
}
// Failsafe to prevent busy-spin.
if (prev_timeout == 0 && !had_event)
timeout = 10;
}
}