[PATCH] mutex subsystem, more debugging code

more mutex debugging: check for held locks during memory freeing,
task exit, enable sysrq printouts, etc.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@infradead.org>

7 files changed, 37 insertions, 0 deletions

diff --git a/arch/i386/mm/pageattr.c b/arch/i386/mm/pageattr.c
index c30a16df6440..e8a53552b13d 100644
--- a/arch/i386/mm/pageattr.c
+++ b/arch/i386/mm/pageattr.c
@@ -222,6 +222,10 @@ void kernel_map_pages(struct page *page, int numpages, int enable)
 {
         if (PageHighMem(page))
                 return;
+        if (!enable)
+                mutex_debug_check_no_locks_freed(page_address(page),
+                                                 page_address(page+numpages));
+
         /* the return value is ignored - the calls cannot fail,
          * large pages are disabled at boot time.
          */
diff --git a/drivers/char/sysrq.c b/drivers/char/sysrq.c
index 145275ebdd7e..5765f672e853 100644
--- a/drivers/char/sysrq.c
+++ b/drivers/char/sysrq.c
@@ -153,6 +153,21 @@ static struct sysrq_key_op sysrq_mountro_op = {
 
 /* END SYNC SYSRQ HANDLERS BLOCK */
 
+#ifdef CONFIG_DEBUG_MUTEXES
+
+static void
+sysrq_handle_showlocks(int key, struct pt_regs *pt_regs, struct tty_struct *tty)
+{
+        mutex_debug_show_all_locks();
+}
+
+static struct sysrq_key_op sysrq_showlocks_op = {
+        .handler        = sysrq_handle_showlocks,
+        .help_msg       = "show-all-locks(D)",
+        .action_msg     = "Show Locks Held",
+};
+
+#endif
 
 /* SHOW SYSRQ HANDLERS BLOCK */
 
@@ -294,7 +309,11 @@ static struct sysrq_key_op *sysrq_key_table[SYSRQ_KEY_TABLE_LENGTH] = {
 #else
 /* c */ NULL,
 #endif
+#ifdef CONFIG_DEBUG_MUTEXES
+/* d */ &sysrq_showlocks_op,
+#else
 /* d */ NULL,
+#endif
 /* e */ &sysrq_term_op,
 /* f */ &sysrq_moom_op,
 /* g */ NULL,
diff --git a/include/linux/mm.h b/include/linux/mm.h
index df80e63903b5..3f1fafc0245e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -13,6 +13,7 @@
 #include <linux/rbtree.h>
 #include <linux/prio_tree.h>
 #include <linux/fs.h>
+#include <linux/mutex.h>
 
 struct mempolicy;
 struct anon_vma;
@@ -1024,6 +1025,9 @@ static inline void vm_stat_account(struct mm_struct *mm,
 static inline void
 kernel_map_pages(struct page *page, int numpages, int enable)
 {
+        if (!PageHighMem(page) && !enable)
+                mutex_debug_check_no_locks_freed(page_address(page),
+                                                 page_address(page + numpages));
 }
 #endif
 
diff --git a/kernel/exit.c b/kernel/exit.c
index caceabf3f230..309a46fa16f8 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -29,6 +29,7 @@
 #include <linux/syscalls.h>
 #include <linux/signal.h>
 #include <linux/cn_proc.h>
+#include <linux/mutex.h>
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -869,6 +870,10 @@ fastcall NORET_TYPE void do_exit(long code)
         mpol_free(tsk->mempolicy);
         tsk->mempolicy = NULL;
 #endif
+        /*
+         * If DEBUG_MUTEXES is on, make sure we are holding no locks:
+         */
+        mutex_debug_check_no_locks_held(tsk);
 
         /* PF_DEAD causes final put_task_struct after we schedule. */
         preempt_disable();
diff --git a/kernel/sched.c b/kernel/sched.c
index 92733091154c..34a945bcc022 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4386,6 +4386,7 @@ void show_state(void)
         } while_each_thread(g, p);
 
         read_unlock(&tasklist_lock);
+        mutex_debug_show_all_locks();
 }
 
 /**
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e0e84924171b..a5e6891f7bb6 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -415,6 +415,9 @@ static void __free_pages_ok(struct page *page, unsigned int order)
         int reserved = 0;
 
         arch_free_page(page, order);
+        if (!PageHighMem(page))
+                mutex_debug_check_no_locks_freed(page_address(page),
+                        page_address(page+(1<<order)));
 
 #ifndef CONFIG_MMU
         for (i = 1 ; i < (1 << order) ; ++i)
diff --git a/mm/slab.c b/mm/slab.c
index 1c46c6383552..33aab345cd4a 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3071,6 +3071,7 @@ void kfree(const void *objp)
         local_irq_save(flags);
         kfree_debugcheck(objp);
         c = page_get_cache(virt_to_page(objp));
+        mutex_debug_check_no_locks_freed(objp, objp+obj_reallen(c));
         __cache_free(c, (void *)objp);
         local_irq_restore(flags);
 }