Author: rwatson
Date: Wed Mar 11 22:00:03 2009
New Revision: 189708
URL: http://svn.freebsd.org/changeset/base/189708
Log:
When writing out updated pollfd records when returning from
poll(), only copy out the revents field, not the whole pollfd
structure. Otherwise, if the events field is updated
concurrently by another thread, that update may be lost.
This issue apparently causes problems for the JDK on FreeBSD,
which expects the Linux behavior of not updating all fields
(somewhat oddly, Solaris does not implement the required
behavior, but presumably our adaptation of the JDK is based
on the Linux port?).
MFC after: 2 weeks
PR: kern/130924
Submitted by: Kurt Miller <kurt @ intricatesoftware.com>
Discussed with: kib
Modified:
head/sys/kern/sys_generic.c
Modified: head/sys/kern/sys_generic.c
==============================================================================
--- head/sys/kern/sys_generic.c Wed Mar 11 21:48:36 2009 (r189707)
+++ head/sys/kern/sys_generic.c Wed Mar 11 22:00:03 2009 (r189708)
@@ -76,6 +76,7 @@ static MALLOC_DEFINE(M_IOCTLOPS, "ioctlo
static MALLOC_DEFINE(M_SELECT, "select", "select() buffer");
MALLOC_DEFINE(M_IOV, "iov", "large iov's");
+static int pollout(struct pollfd *, struct pollfd *, u_int);
static int pollscan(struct thread *, struct pollfd *, u_int);
static int pollrescan(struct thread *);
static int selscan(struct thread *, fd_mask **, fd_mask **, int);
@@ -1128,7 +1129,7 @@ done:
if (error == EWOULDBLOCK)
error = 0;
if (error == 0) {
- error = copyout(bits, uap->fds, ni);
+ error = pollout(bits, uap->fds, nfds);
if (error)
goto out;
}
@@ -1183,6 +1184,26 @@ pollrescan(struct thread *td)
static int
+pollout(fds, ufds, nfd)
+ struct pollfd *fds;
+ struct pollfd *ufds;
+ u_int nfd;
+{
+ int error = 0;
+ u_int i = 0;
+
+ for (i = 0; i < nfd; i++) {
+ error = copyout(&fds->revents, &ufds->revents,
+ sizeof(ufds->revents));
+ if (error)
+ return (error);
+ fds++;
+ ufds++;
+ }
+ return (0);
+}
+
+static int
pollscan(td, fds, nfd)
struct thread *td;
struct pollfd *fds;
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