devmnt: fix potential race with mntflushfree(), remove mntstats, 0 vs nil cleanup

when mountmux() completes a request for another process, enforce odering
of the loads and stores to the request prior to writing q->done = 1
so mntflushfree() sees q->done != 0 only when the request has actually
completed. otherwise, the q->done = 1 store could have been reordered
before the load from q->z, reading from already freed request and causing
spurious wakeups.

removing unused mntstats callback.

use nil for pointers instead of 0.

0 files changed, 0 insertions, 0 deletions