Changeset 90c8b8d in mainline for kernel/generic/src/synch/spinlock.c

Timestamp:

2009-08-21T14:08:20Z (15 years ago)

Author:

Martin Decky <martin@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

a71c158

Parents:

af8e565

Message:

extend the spinlock interface (static spinlocks, statically declared spinlocks with user-defined name)
ignore deadlock detection on all spinlocks whose name begins with "*" (this is more generic than a hardwired list of spinlocks to ignore)
printf_lock is not required to be public anymore

File:

• kernel/generic/src/synch/spinlock.c (modified) (5 diffs)

kernel/generic/src/synch/spinlock.c

@@ -45 +45 @@
 #include <symtab.h>
 
-#ifdef CONFIG_FB
-#include <genarch/fb/fb.h>
-#endif
-
 #ifdef CONFIG_SMP
 
 /** Initialize spinlock
  *
- * Initialize spinlock.
+ * @param sl Pointer to spinlock_t structure.
  *
- * @param sl Pointer to spinlock_t structure.
  */
-void spinlock_initialize(spinlock_t *sl, char *name)
+void spinlock_initialize(spinlock_t *lock, char *name)
 {
-        atomic_set(&sl->val, 0);
+        atomic_set(&lock->val, 0);
 #ifdef CONFIG_DEBUG_SPINLOCK
-        sl->name = name;
-#endif  
+        lock->name = name;
+#endif
 }
+
+#ifdef CONFIG_DEBUG_SPINLOCK
 
 /** Lock spinlock
@@ -71 +68 @@
  * possible occurence of deadlock.
  *
- * @param sl Pointer to spinlock_t structure.
+ * @param lock Pointer to spinlock_t structure.
+ *
  */
-#ifdef CONFIG_DEBUG_SPINLOCK
-void spinlock_lock_debug(spinlock_t *sl)
+void spinlock_lock_debug(spinlock_t *lock)
 {
         size_t i = 0;
         bool deadlock_reported = false;
-
+        
         preemption_disable();
-        while (test_and_set(&sl->val)) {
-
+        while (test_and_set(&lock->val)) {
                 /*
-                 * We need to be careful about printf_lock and fb_lock.
-                 * Both of them are used to report deadlocks via
-                 * printf() and fb_putchar().
+                 * We need to be careful about particular locks
+                 * which are directly used to report deadlocks
+                 * via printf() (and recursively other functions).
+                 * This conserns especially printf_lock and the
+                 * framebuffer lock.
                  *
+                 * Any lock whose name is prefixed by "*" will be
+                 * ignored by this deadlock detection routine
+                 * as this might cause an infinite recursion.
                  * We trust our code that there is no possible deadlock
-                 * caused by these two locks (except when an exception
-                 * is triggered for instance by printf() or fb_putchar()).
-                 * However, we encountered false positives caused by very
-                 * slow VESA framebuffer interaction (especially when
+                 * caused by these locks (except when an exception
+                 * is triggered for instance by printf()).
+                 *
+                 * We encountered false positives caused by very
+                 * slow framebuffer interaction (especially when
                  * run in a simulator) that caused problems with both
-                 * printf_lock and fb_lock.
+                 * printf_lock and the framebuffer lock.
                  *
-                 * Possible deadlocks on both printf_lock and fb_lock
-                 * are therefore not reported as they would cause an
-                 * infinite recursion.
                  */
-                if (sl == &printf_lock)
+                if (lock->name[0] == '*')
                         continue;
-#ifdef CONFIG_FB
-                if (sl == &fb_lock)
-                        continue;
-#endif
+                
                 if (i++ > DEADLOCK_THRESHOLD) {
                         printf("cpu%u: looping on spinlock %" PRIp ":%s, "
-                            "caller=%" PRIp "(%s)\n", CPU->id, sl, sl->name,
+                            "caller=%" PRIp "(%s)\n", CPU->id, lock, lock->name,
                             CALLER, symtab_fmt_name_lookup(CALLER));
                         
@@ -114 +110 @@
                 }
         }
-
+        
         if (deadlock_reported)
                 printf("cpu%u: not deadlocked\n", CPU->id);
-
+        
         /*
          * Prevent critical section code from bleeding out this way up.
@@ -123 +119 @@
         CS_ENTER_BARRIER();
 }
+
 #endif
 
@@ -131 +128 @@
  * signal failure.
  *
- * @param sl Pointer to spinlock_t structure.
+ * @param lock Pointer to spinlock_t structure.
  *
  * @return Zero on failure, non-zero otherwise.
+ *
  */
-int spinlock_trylock(spinlock_t *sl)
+int spinlock_trylock(spinlock_t *lock)
 {
-        int rc;
+        preemption_disable();
+        int rc = !test_and_set(&lock->val);
         
-        preemption_disable();
-        rc = !test_and_set(&sl->val);
-
         /*
          * Prevent critical section code from bleeding out this way up.
          */
         CS_ENTER_BARRIER();
-
+        
         if (!rc)
                 preemption_enable();