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Subject[PATCH] UP spinlock debugging
Hi Linus,

the attached patch adds support for spinlock debugging with uniprocessor
kernels:

* new config option CONFIG_DEBUG_SPINLOCK_UP
* CONFIG_DEBUG_SPINLOCK only works on SMP, SMP added to config string
* support for directly including <asm/spinlock.h> removed from
<linux/spinlock.h>
Doesn't work anyway, probably the '!defined(spin_lock_init)'
was overlooked.
* DEBUG_SPINLOCKS==2 macros indented
* spin_lock saves the current owner into the spinlock structure,
file name+line printed on deadlock.
* stricter spin_trylock and spin_is_locked.

Patch against 2.4.10, tested with 2.4.10 i386

Could you apply it to the next -pre kernel?

--
Manfred
<<<<<<<<<<<<<<
// Kernel Version:
// VERSION = 2
// PATCHLEVEL = 4
// SUBLEVEL = 10
// EXTRAVERSION =
--- 2.4/arch/i386/config.in Sun Sep 23 21:20:24 2001
+++ build-2.4/arch/i386/config.in Sun Sep 30 16:10:06 2001
@@ -396,7 +396,12 @@
bool ' Debug memory allocations' CONFIG_DEBUG_SLAB
bool ' Memory mapped I/O debugging' CONFIG_DEBUG_IOVIRT
bool ' Magic SysRq key' CONFIG_MAGIC_SYSRQ
- bool ' Spinlock debugging' CONFIG_DEBUG_SPINLOCK
+ if [ "$CONFIG_SMP" = "y" ]; then
+ bool ' Spinlock debugging (SMP)' CONFIG_DEBUG_SPINLOCK
+ fi
+ if [ "$CONFIG_SMP" = "n" ]; then
+ bool ' Spinlock debugging (UP)' CONFIG_DEBUG_SPINLOCK_UP
+ fi
bool ' Verbose BUG() reporting (adds 70K)' CONFIG_DEBUG_BUGVERBOSE
fi

--- 2.4/include/linux/spinlock.h Sat Jul 21 22:09:10 2001
+++ build-2.4/include/linux/spinlock.h Sun Sep 30 16:58:22 2001
@@ -33,12 +33,13 @@

#ifdef CONFIG_SMP
#include <asm/spinlock.h>
+#else

-#elif !defined(spin_lock_init) /* !SMP and spin_lock_init not previously
- defined (e.g. by including asm/spinlock.h */
-
-#define DEBUG_SPINLOCKS 0 /* 0 == no debugging, 1 == maintain lock state, 2 == full debug */
-
+#ifdef CONFIG_DEBUG_SPINLOCK_UP
+#define DEBUG_SPINLOCKS 2 /* 0 == no debugging, 1 == maintain lock state, 2 == full debug */
+#else
+#define DEBUG_SPINLOCKS 0
+#endif
#if (DEBUG_SPINLOCKS < 1)

#define atomic_dec_and_lock(atomic,lock) atomic_dec_and_test(atomic)
@@ -84,18 +85,81 @@
volatile unsigned long lock;
volatile unsigned int babble;
const char *module;
+ char *owner;
+ int oline;
} spinlock_t;
-#define SPIN_LOCK_UNLOCKED (spinlock_t) { 0, 25, __BASE_FILE__ }
+#define SPIN_LOCK_UNLOCKED (spinlock_t) { 0, 10, __BASE_FILE__ , NULL, 0}

#include <linux/kernel.h>

-#define spin_lock_init(x) do { (x)->lock = 0; } while (0)
-#define spin_is_locked(lock) (test_bit(0,(lock)))
-#define spin_trylock(lock) (!test_and_set_bit(0,(lock)))
-
-#define spin_lock(x) do {unsigned long __spinflags; save_flags(__spinflags); cli(); if ((x)->lock&&(x)->babble) {printk("%s:%d: spin_lock(%s:%p) already locked\n", __BASE_FILE__,__LINE__, (x)->module, (x));(x)->babble--;} (x)->lock = 1; restore_flags(__spinflags);} while (0)
-#define spin_unlock_wait(x) do {unsigned long __spinflags; save_flags(__spinflags); cli(); if ((x)->lock&&(x)->babble) {printk("%s:%d: spin_unlock_wait(%s:%p) deadlock\n", __BASE_FILE__,__LINE__, (x)->module, (x));(x)->babble--;} restore_flags(__spinflags);} while (0)
-#define spin_unlock(x) do {unsigned long __spinflags; save_flags(__spinflags); cli(); if (!(x)->lock&&(x)->babble) {printk("%s:%d: spin_unlock(%s:%p) not locked\n", __BASE_FILE__,__LINE__, (x)->module, (x));(x)->babble--;} (x)->lock = 0; restore_flags(__spinflags);} while (0)
+#define spin_lock_init(x) \
+ do { \
+ (x)->lock = 0; \
+ (x)->babble = 5; \
+ (x)->module = __BASE_FILE__; \
+ (x)->owner = NULL; \
+ (x)->oline = 0; \
+ } while (0)
+/* without debugging, spin_is_locked on UP always says
+ * FALSE. --> printk if already locked. */
+#define spin_is_locked(x) \
+ ({ \
+ if ((x)->lock&&(x)->babble) { \
+ printk("%s:%d: spin_is_locked(%s:%p) already locked by %s/%d\n", \
+ __BASE_FILE__,__LINE__, (x)->module, \
+ (x), (x)->owner, (x)->oline); \
+ (x)->babble--; \
+ } \
+ 0; \
+ })
+
+/* without debugging, spin_trylock on UP always says
+ * TRUE. --> printk if already locked. */
+#define spin_trylock(x) \
+ ({ \
+ if ((x)->lock&&(x)->babble) { \
+ printk("%s:%d: spin_trylock(%s:%p) already locked by %s/%d\n", \
+ __BASE_FILE__,__LINE__, (x)->module, \
+ (x), (x)->owner, (x)->oline); \
+ (x)->babble--; \
+ } \
+ (x)->lock = 1; \
+ (x)->owner = __BASE_FILE__; \
+ (x)->oline = __LINE__; \
+ 1; \
+ })
+
+#define spin_lock(x) \
+ do { \
+ if ((x)->lock&&(x)->babble) { \
+ printk("%s:%d: spin_lock(%s:%p) already locked by %s/%d\n", \
+ __BASE_FILE__,__LINE__, (x)->module, \
+ (x), (x)->owner, (x)->oline); \
+ (x)->babble--; \
+ } \
+ (x)->lock = 1; \
+ (x)->owner = __BASE_FILE__; \
+ (x)->oline = __LINE__; \
+ } while (0)
+
+#define spin_unlock_wait(x) \
+ do { \
+ if ((x)->lock&&(x)->babble) { \
+ printk("%s:%d: spin_unlock_wait(%s:%p) owned by %s/%d\n", \
+ __BASE_FILE__,__LINE__, (x)->module, (x), \
+ (x)->owner, (x)->oline); \
+ (x)->babble--; \
+ }\
+ } while (0)
+#define spin_unlock(x) \
+ do { \
+ if (!(x)->lock&&(x)->babble) { \
+ printk("%s:%d: spin_unlock(%s:%p) not locked\n", \
+ __BASE_FILE__,__LINE__, (x)->module, (x));\
+ (x)->babble--; \
+ } \
+ (x)->lock = 0; \
+ } while (0)

#endif /* DEBUG_SPINLOCKS */

--- 2.4/kernel/ksyms.c Sun Sep 23 21:20:55 2001
+++ build-2.4/kernel/ksyms.c Sun Sep 30 17:07:53 2001
@@ -376,10 +376,12 @@
EXPORT_SYMBOL(tq_timer);
EXPORT_SYMBOL(tq_immediate);

-#ifdef CONFIG_SMP
+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK_UP)
/* Various random spinlocks we want to export */
EXPORT_SYMBOL(tqueue_lock);
+#endif

+#ifdef CONFIG_SMP
/* Big-Reader lock implementation */
EXPORT_SYMBOL(__brlock_array);
#ifndef __BRLOCK_USE_ATOMICS
-
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