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use poll(2) rather than select(2) for reading output from an exec'ed process

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select(2) can only handle file descriptors up to 1024, and there are fairly easy to reproduce
cases where the file descriptor used here is larger than that.
This commit is contained in:
Paul Davis 2021-05-06 14:38:35 -06:00
parent 221b272f8a
commit 3a7ea6b217
1 changed files with 20 additions and 8 deletions
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28
libs/pbd/system_exec.cc
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@ -18,6 +18,7 @@
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <poll.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@ -835,17 +836,28 @@ SystemExec::output_interposer ()
for (;fcntl (rfd, F_GETFL) != -1;) {
r = read (rfd, buf, BUFSIZ - 1);
if (r < 0 && (errno == EINTR || errno == EAGAIN)) {
fd_set rfds;
struct timeval tv;
FD_ZERO (&rfds);
FD_SET (rfd, &rfds);
tv.tv_sec = 0;
tv.tv_usec = 10000;
int rv = select (1, &rfds, NULL, NULL, &tv);
/* wait till ready to read */
struct pollfd pfd;
pfd.fd = rfd;
pfd.events = POLLIN|POLLERR|POLLHUP;
int rv = poll (&pfd, 1, 10000);
if (rv == -1) {
break;
}
continue;
if (pfd.revents & (POLLERR|POLLHUP)) {
break;
}
if (rv == 1 && pfd.revents & POLLIN) {
/* back to read(2) call */
continue;
}
}
if (r <= 0) {
break;