lkml.org 
[lkml]   [2001]   [Dec]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH] improve spinlock debugging
CONFIG_DEBUG_SPINLOCK only adds spinlock tests for SMP builds. The
attached patch adds runtime checks for uniprocessor builds.

Tested on i386/UP, but it should work on all platforms. It contains
runtime checks for:

- missing initialization
- recursive lock
- double unlock
- incorrect use of spin_is_locked() or spin_trylock() [both function
do not work as expected on uniprocessor builds]
The next step are checks for spinlock ordering mismatches.

Which other runtime checks are possible?
Tests for correct _irq usage are not possible, several drivers use
disable_irq().

--
Manfred// $Header$
// Kernel Version:
// VERSION = 2
// PATCHLEVEL = 5
// SUBLEVEL = 1
// EXTRAVERSION =-pre5
--- 2.5/include/linux/spinlock.h Fri Oct 26 17:03:12 2001
+++ build-2.5/include/linux/spinlock.h Mon Dec 3 19:45:58 2001
@@ -37,12 +37,13 @@

#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
+#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)
@@ -85,22 +86,101 @@

#else /* (DEBUG_SPINLOCKS >= 2) */

+#define SPINLOCK_MAGIC 0x1D244B3C
typedef struct {
+ unsigned long magic;
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) { SPINLOCK_MAGIC, 0, 10, __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)->magic = SPINLOCK_MAGIC; \
+ (x)->lock = 0; \
+ (x)->babble = 5; \
+ (x)->module = __FILE__; \
+ (x)->owner = NULL; \
+ (x)->oline = 0; \
+ } while (0)
+#define CHECK_LOCK(x) \
+ do { \
+ if ((x)->magic != SPINLOCK_MAGIC) { \
+ printk(KERN_ERR "%s:%d: spin_is_locked on uninitialized spinlock %p.\n", \
+ __FILE__, __LINE__, (x)); \
+ } \
+ } while(0)
+/* without debugging, spin_is_locked on UP always says
+ * FALSE. --> printk if already locked. */
+#define spin_is_locked(x) \
+ ({ \
+ CHECK_LOCK(x); \
+ if ((x)->lock&&(x)->babble) { \
+ printk("%s:%d: spin_is_locked(%s:%p) already locked by %s/%d\n", \
+ __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) \
+ ({ \
+ CHECK_LOCK(x); \
+ if ((x)->lock&&(x)->babble) { \
+ printk("%s:%d: spin_trylock(%s:%p) already locked by %s/%d\n", \
+ __FILE__,__LINE__, (x)->module, \
+ (x), (x)->owner, (x)->oline); \
+ (x)->babble--; \
+ } \
+ (x)->lock = 1; \
+ (x)->owner = __FILE__; \
+ (x)->oline = __LINE__; \
+ 1; \
+ })
+
+#define spin_lock(x) \
+ do { \
+ CHECK_LOCK(x); \
+ if ((x)->lock&&(x)->babble) { \
+ printk("%s:%d: spin_lock(%s:%p) already locked by %s/%d\n", \
+ __FILE__,__LINE__, (x)->module, \
+ (x), (x)->owner, (x)->oline); \
+ (x)->babble--; \
+ } \
+ (x)->lock = 1; \
+ (x)->owner = __FILE__; \
+ (x)->oline = __LINE__; \
+ } while (0)
+
+#define spin_unlock_wait(x) \
+ do { \
+ CHECK_LOCK(x); \
+ if ((x)->lock&&(x)->babble) { \
+ printk("%s:%d: spin_unlock_wait(%s:%p) owned by %s/%d\n", \
+ __FILE__,__LINE__, (x)->module, (x), \
+ (x)->owner, (x)->oline); \
+ (x)->babble--; \
+ }\
+ } while (0)
+
+#define spin_unlock(x) \
+ do { \
+ CHECK_LOCK(x); \
+ if (!(x)->lock&&(x)->babble) { \
+ printk("%s:%d: spin_unlock(%s:%p) not locked\n", \
+ __FILE__,__LINE__, (x)->module, (x));\
+ (x)->babble--; \
+ } \
+ (x)->lock = 0; \
+ } while (0)

#endif /* DEBUG_SPINLOCKS */

--- 2.5/kernel/ksyms.c Mon Dec 3 18:30:08 2001
+++ build-2.5/kernel/ksyms.c Mon Dec 3 20:06:49 2001
@@ -381,10 +381,10 @@
EXPORT_SYMBOL(tq_timer);
EXPORT_SYMBOL(tq_immediate);

-#ifdef CONFIG_SMP
/* Various random spinlocks we want to export */
EXPORT_SYMBOL(tqueue_lock);

+#ifdef CONFIG_SMP
/* Big-Reader lock implementation */
EXPORT_SYMBOL(__brlock_array);
#ifndef __BRLOCK_USE_ATOMICS
--- 2.5/Documentation/Configure.help Mon Dec 3 18:30:07 2001
+++ build-2.5/Documentation/Configure.help Mon Dec 3 20:31:40 2001
@@ -23565,8 +23565,10 @@

Spinlock debugging
CONFIG_DEBUG_SPINLOCK
- Say Y here and build SMP to catch missing spinlock initialization
- and certain other kinds of spinlock errors commonly made. This is
+ Say Y here to add additional runtime checks into the spinlock
+ functions. On UP it detects missing initializations and simple
+ deadlocks. On SMP it finds missing initializations and certain other
+ kinds of spinlock errors commonly made, excluding deadlocks. This is
best used in conjunction with the NMI watchdog so that spinlock
deadlocks are also debuggable.


\
 
 \ /
  Last update: 2005-03-22 13:13    [W:0.112 / U:14.552 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site