From 52602010f08ae13a65603417ca667757a2b7eacf Mon Sep 17 00:00:00 2001 From: Brian Feldman Date: Wed, 20 Oct 2004 23:22:56 +0000 Subject: The BSD patchset for the Sun JDK modeled its thread behavior mostly after existing the Solaris base, and similarly to what happened with NSPR, made a bad assumption on undefined behavior. This broke locking in various places in Java, for example, causing the the debugging support to be totally broken. It is worth someone who knows the Java codebase taking a look to see what other things could have been broken by this on FreeBSD 5.x+. The assumption is that pthread_mutex_trylock(3) on a default-type mutex will fail with EBUSY. This assumption is wrong for our libpthread, which returns EDEADLK if the owner thread is trying to acquire the mutex again with trylock. The behavior of performing a locking operation on a self-locked default-type mutex is explicitly undefined for pthread_mutex_lock(3). The POSIX specification is still not very clear. It defines pthread_mutex_trylock(3) in terms of pthread_mutex_lock(3) yet does not say what the defined behavior should be for a self-locked pthread_mutex_trylock(3) for any of the various mutex types, so it is ambiguous whether the result is clearly undefined or clearly to return EBUSY. It is a one line change whether or not to make libpthread return EDEADLK in this case, where it seems that most implementations do not. Reference: http://www.opengroup.org/onlinepubs/009695399/functions/pthread_mutex_lock.html --- java/jdk16/files/patch-vm::os_bsd.hpp | 13 +++++++++++++ 1 file changed, 13 insertions(+) create mode 100644 java/jdk16/files/patch-vm::os_bsd.hpp (limited to 'java/jdk16/files') diff --git a/java/jdk16/files/patch-vm::os_bsd.hpp b/java/jdk16/files/patch-vm::os_bsd.hpp new file mode 100644 index 000000000000..cab94f46e4d3 --- /dev/null +++ b/java/jdk16/files/patch-vm::os_bsd.hpp @@ -0,0 +1,13 @@ +$FreeBSD$ + +--- ../../hotspot/src/os/bsd/vm/os_bsd.hpp.orig Wed Oct 20 16:01:08 2004 ++++ ../../hotspot/src/os/bsd/vm/os_bsd.hpp Wed Oct 20 16:01:30 2004 +@@ -353,7 +353,7 @@ + bool trylock() { + verify(); + int status = pthread_mutex_trylock(_mutex); +- if (status == EBUSY) ++ if (status == EBUSY || status == EDEADLK) + return false; + assert(status == 0, "pthread_mutex_trylock"); + #ifndef PRODUCT -- cgit v1.2.3