On Jul 29, 2009, at 1:10 AM, Pawel Jakub Dawidek wrote:
On Tue, Jul 28, 2009 at 02:09:07PM +0000, Randall Stewart wrote:
Author: rrs
Date: Tue Jul 28 14:09:06 2009
New Revision: 195918
URL: http://svn.freebsd.org/changeset/base/195918
Log:
Turns out that when a receiver forwards through its TNS's the
processing code holds the read lock (when processing a
FWD-TSN for pr-sctp). If it finds stranded data that
can be given to the application, it calls sctp_add_to_readq().
The readq function also grabs this lock. So if INVAR is on
we get a double recurse on a non-recursive lock and panic.
This fix will change it so that readq() function gets a
flag to tell if the lock is held, if so then it does not
get the lock.
Approved by: r...@freebsd.org (Kostik Belousov)
MFC after: 1 week
[...]
sctp_add_to_readq(stcb->sctp_ep, stcb, control,
- &stcb->sctp_socket->so_rcv, 1, so_locked);
+ &stcb->sctp_socket->so_rcv, 1, SCTP_READ_LOCK_NOT_HELD,
so_locked);
[...]
@@ -4301,6 +4306,7 @@ sctp_add_to_readq(struct sctp_inpcb *inp
struct sctp_queued_to_read *control,
struct sockbuf *sb,
int end,
+ int inp_read_lock_held,
int so_locked
#if !defined(__APPLE__) && !defined(SCTP_SO_LOCK_TESTING)
SCTP_UNUSED
@@ -4321,7 +4327,8 @@ sctp_add_to_readq(struct sctp_inpcb *inp
#endif
return;
}
- SCTP_INP_READ_LOCK(inp);
+ if (inp_read_lock_held == 0)
It would be a bit cleaner to compare with SCTP_READ_LOCK_NOT_HELD
here,
instead of 0.
I suppose so ;-)
+ SCTP_INP_READ_LOCK(inp);
if (!(control->spec_flags & M_NOTIFICATION)) {
atomic_add_int(&inp->total_recvs, 1);
if (!control->do_not_ref_stcb) {
@@ -4362,14 +4369,16 @@ sctp_add_to_readq(struct sctp_inpcb *inp
control->tail_mbuf = prev;
} else {
/* Everything got collapsed out?? */
- SCTP_INP_READ_UNLOCK(inp);
+ if (inp_read_lock_held == 0)
+ SCTP_INP_READ_UNLOCK(inp);
return;
}
if (end) {
control->end_added = 1;
}
TAILQ_INSERT_TAIL(&inp->read_queue, control, next);
- SCTP_INP_READ_UNLOCK(inp);
+ if (inp_read_lock_held == 0)
+ SCTP_INP_READ_UNLOCK(inp);
if (inp && inp->sctp_socket) {
if (sctp_is_feature_on(inp, SCTP_PCB_FLAGS_ZERO_COPY_ACTIVE)) {
SCTP_ZERO_COPY_EVENT(inp, inp->sctp_socket);
Instead of using additional argument to the sctp_add_to_readq()
function, wouldn't it be sufficient to just check with mtx_owned(9) if
the lock is already held?
Hmm... I suppose one could go that way... but traditionally upper code
as
told the lower code that it holds/does not hold the lock. This is true
in quite a few other functions...
R
--
Pawel Jakub Dawidek http://www.wheel.pl
p...@freebsd.org http://www.FreeBSD.org
FreeBSD committer Am I Evil? Yes, I Am!
------------------------------
Randall Stewart
803-317-4952 (cell)
803-345-0391(direct)
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