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fusefs: fix intermittency in the dev_fuse_poll test

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The DevFusePoll::access/select test would occasionally segfault.  The
cause was a file descriptor that was shared between two threads.  The
first thread would kill the second and close the file descriptor.  But
it was possible that the second would read the file descriptor before it
shut down.  That did not cause problems for kqueue, poll, or blocking
operation, but it triggered segfaults in select's macros.

MFC after:	2 weeks
Differential Revision: https://reviews.freebsd.org/D32142
This commit is contained in:
Alan Somers 2021-09-25 10:16:20 -06:00
parent 880b670c6f
commit f44a448709
2 changed files with 8 additions and 4 deletions
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10
tests/sys/fs/fusefs/mockfs.cc
View File

@ -870,6 +870,7 @@ void MockFS::read_request(mockfs_buf_in &in, ssize_t &res) {
struct timeval timeout_tv;
const int timeout_ms = 999;
int timeout_int, nfds;
int fuse_fd;
switch (m_pm) {
case BLOCKING:
@ -906,19 +907,22 @@ void MockFS::read_request(mockfs_buf_in &in, ssize_t &res) {
ASSERT_TRUE(fds[0].revents & POLLIN);
break;
case SELECT:
fuse_fd = m_fuse_fd;
if (fuse_fd < 0)
break;
timeout_tv.tv_sec = 0;
timeout_tv.tv_usec = timeout_ms * 1'000;
nfds = m_fuse_fd + 1;
nfds = fuse_fd + 1;
while (nready == 0) {
FD_ZERO(&readfds);
FD_SET(m_fuse_fd, &readfds);
FD_SET(fuse_fd, &readfds);
nready = select(nfds, &readfds, NULL, NULL,
&timeout_tv);
if (m_quit)
return;
}
ASSERT_LE(0, nready) << strerror(errno);
ASSERT_TRUE(FD_ISSET(m_fuse_fd, &readfds));
ASSERT_TRUE(FD_ISSET(fuse_fd, &readfds));
break;
default:
FAIL() << "not yet implemented";

2
tests/sys/fs/fusefs/mockfs.hh
View File

@ -284,7 +284,7 @@ class MockFS {
pthread_t m_daemon_id;
/* file descriptor of /dev/fuse control device */
int m_fuse_fd;
volatile int m_fuse_fd;
/* The minor version of the kernel API that this mock daemon targets */
uint32_t m_kernel_minor_version;