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* Ugly hack to handle spurious SIGPOLLs.

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This commit is contained in:
Eelco Dolstra 2006-12-05 15:36:31 +00:00
parent fd4a9db91f
commit c808e6252f
1 changed files with 50 additions and 20 deletions
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60
src/nix-worker/main.cc
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@ -49,6 +49,34 @@ static void tunnelStderr(const unsigned char * buf, size_t count)
}
/* Return true if the remote side has closed its end of the
connection, false otherwise. Should not be called on any socket on
which we expect input! */
static bool isFarSideClosed(int socket)
{
struct timeval timeout;
timeout.tv_sec = timeout.tv_usec = 0;
fd_set fds;
FD_ZERO(&fds);
FD_SET(socket, &fds);
if (select(socket + 1, &fds, 0, 0, &timeout) == -1)
throw SysError("select()");
if (!FD_ISSET(socket, &fds)) return false;
/* Destructive read to determine whether the select() marked the
socket as readable because there is actual input or because
we've reached EOF (i.e., a read of size 0 is available). */
char c;
if (read(socket, &c, 1) != 0)
throw Error("EOF expected (protocol error?)");
return true;
}
/* A SIGPOLL signal is received when data is available on the client
communication scoket, or when the client has closed its side of the
socket. This handler is enabled at precisely those moments in the
@ -62,12 +90,28 @@ static void tunnelStderr(const unsigned char * buf, size_t count)
time and wouldn't have to worry about races. */
static void sigPollHandler(int sigNo)
{
try {
/* Check that the far side actually closed. We're still
getting spurious signals every once in a while. I.e.,
there is no input available, but we get a signal with
POLL_IN set. Maybe it's delayed or something. */
if (isFarSideClosed(from.fd)) {
if (!blockInt) {
_isInterrupted = 1;
blockInt = 1;
canSendStderr = false;
write(STDERR_FILENO, "SIGPOLL\n", 8);
}
} else {
string s = "spurious SIGPOLL\n";
write(STDERR_FILENO, s.c_str(), s.size());
}
}
catch (Error & e) {
/* Shouldn't happen. */
write(STDERR_FILENO, e.msg().c_str(), e.msg().size());
abort();
}
}
@ -98,21 +142,7 @@ static void startWork()
out if any input is available on the socket. If there is, it
has to be the 0-byte read that indicates that the socket has
closed. */
struct timeval timeout;
timeout.tv_sec = timeout.tv_usec = 0;
fd_set fds;
FD_ZERO(&fds);
FD_SET(from.fd, &fds);
if (select(from.fd + 1, &fds, 0, 0, &timeout) == -1)
throw SysError("select()");
if (FD_ISSET(from.fd, &fds)) {
char c;
if (read(from.fd, &c, 1) != 0)
throw Error("EOF expected (protocol error?)");
if (isFarSideClosed(from.fd)) {
_isInterrupted = 1;
checkInterrupt();
}