Fix mtx_legal2block. The only time that it is bad to block on a mutex is

if we hold a spin mutex, since we can trivially get into deadlocks if we
start switching out of processes that hold spinlocks.  Checking to see if
interrupts were disabled was a sort of cheap way of doing this since most
of the time interrupts were only disabled when holding a spin lock.  At
least on the i386.  To fix this properly, use a per-process counter
p_spinlocks that counts the number of spin locks currently held, and
instead of checking to see if interrupts are disabled in the witness code,
check to see if we hold any spin locks.  Since child processes always
start up with the sched lock magically held in fork_exit(), we initialize
p_spinlocks to 1 for child processes.  Note that proc0 doesn't go through
fork_exit(), so it starts with no spin locks held.

Consulting from:	cp

1 files changed, 0 insertions, 1 deletions

diff --git a/sys/i386/include/mutex.h b/sys/i386/include/mutex.h
index a5f88de..4184cde 100644
--- a/sys/i386/include/mutex.h
+++ b/sys/i386/include/mutex.h
@@ -40,7 +40,6 @@
 /* Global locks */
 extern struct mtx	clock_lock;
 
-#define	mtx_legal2block()	(read_eflags() & PSL_I)
 #define	mtx_intr_enable(mutex)	(mutex)->mtx_saveintr |= PSL_I
 
 /*