Added function read_cpu_flags() that returns current cpu flags as a

long.  This is used to check for interrupts being disabled at the time
of a lock() call, if enabled in config.h. The number of times this
happens is then counted in the kinfo structure. These events (recursive
lockings) lead to nasty race conditions.

kernel/const.h

@@ -3,6 +3,7 @@
 #include <ibm/interrupt.h>	/* interrupt numbers and hardware vectors */
 #include <ibm/ports.h>		/* port addresses and magic numbers */
 #include <ibm/bios.h>		/* BIOS addresses, sizes and magic numbers */
+#include <ibm/cpu.h>		/* BIOS addresses, sizes and magic numbers */
 #include <minix/config.h>
 
 /* To translate an address in kernel space to a physical address.  This is
@@ -73,8 +74,14 @@
 #define locktimeend(c)
 #endif
 
+#if ENABLE_K_LOCKCHECK
+#define lockcheck if(!(read_cpu_flags() & X86_FLAG_I)) kinfo.relocking++;
+#else
+#define lockcheck
+#endif
+
 /* Disable/Enable hardware interrupts. */
-#define lock(c, v)	do { intr_disable(); locktimestart(c, v); } while(0)
+#define lock(c, v)	do { lockcheck; intr_disable(); locktimestart(c, v); } while(0)
 #define unlock(c)	do { locktimeend(c); intr_enable(); } while(0)
 
 /* Sizes of memory tables. The boot monitor distinguishes three memory areas, 

kernel/klib386.s

@@ -32,6 +32,7 @@
 .define	_idle_task	! task executed when there is no work
 .define	_level0		! call a function at level 0
 .define	_read_tsc	! read the cycle counter (Pentium and up)
+.define	_read_cpu_flags	! read the cpu flags
 
 ! The routines only guarantee to preserve the registers the C compiler
 ! expects to be preserved (ebx, esi, edi, ebp, esp, segment registers, and
@@ -546,3 +547,15 @@ _read_tsc:
 	pop ebp
 	ret
 
+!*===========================================================================*
+!*			      read_flags					     *
+!*===========================================================================*
+! PUBLIC unsigned long read_cpu_flags(void);
+! Read the cycle counter of the CPU. Pentium and up. 
+.align 16
+_read_cpu_flags:
+	pushf
+	mov eax, (esp)
+	popf
+	ret
+

kernel/main.c

@@ -180,6 +180,7 @@ PRIVATE void announce(void)
   /* Check if boot device was loaded with the kernel. */
   if (kinfo.bootdev_base > 0)
       kprintf("Image of /dev/boot loaded. Size: %u KB.\n", kinfo.bootdev_size);
+
 }
 
 

kernel/proto.h

@@ -97,6 +97,7 @@ _PROTOTYPE( void reset, (void)						);
 _PROTOTYPE( void level0, (void (*func)(void))				);
 _PROTOTYPE( void monitor, (void)					);
 _PROTOTYPE( void read_tsc, (unsigned long *high, unsigned long *low)	);
+_PROTOTYPE( unsigned long read_cpu_flags, (void)			);
 
 /* mpx*.s */
 _PROTOTYPE( void idle_task, (void)					);