locking/lockdep: Implement the 'crossrelease' feature

Lockdep is a runtime locking correctness validator that detects and
reports a deadlock or its possibility by checking dependencies between
locks. It's useful since it does not report just an actual deadlock but
also the possibility of a deadlock that has not actually happened yet.
That enables problems to be fixed before they affect real systems.

However, this facility is only applicable to typical locks, such as
spinlocks and mutexes, which are normally released within the context in
which they were acquired. However, synchronization primitives like page
locks or completions, which are allowed to be released in any context,
also create dependencies and can cause a deadlock.

So lockdep should track these locks to do a better job. The 'crossrelease'
implementation makes these primitives also be tracked.

Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: akpm@linux-foundation.org
Cc: boqun.feng@gmail.com
Cc: kernel-team@lge.com
Cc: kirill@shutemov.name
Cc: npiggin@gmail.com
Cc: walken@google.com
Cc: willy@infradead.org
Link: http://lkml.kernel.org/r/1502089981-21272-6-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 103 insertions, 7 deletions

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 0a4c02c2d7a2..e1e0fcd99613 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -155,6 +155,12 @@ struct lockdep_map {
         int                             cpu;
         unsigned long                   ip;
 #endif
+#ifdef CONFIG_LOCKDEP_CROSSRELEASE
+        /*
+         * Whether it's a crosslock.
+         */
+        int                             cross;
+#endif
 };
 
 static inline void lockdep_copy_map(struct lockdep_map *to,
@@ -258,8 +264,62 @@ struct held_lock {
         unsigned int hardirqs_off:1;
         unsigned int references:12;                                     /* 32 bits */
         unsigned int pin_count;
+#ifdef CONFIG_LOCKDEP_CROSSRELEASE
+        /*
+         * Generation id.
+         *
+         * A value of cross_gen_id will be stored when holding this,
+         * which is globally increased whenever each crosslock is held.
+         */
+        unsigned int gen_id;
+#endif
+};
+
+#ifdef CONFIG_LOCKDEP_CROSSRELEASE
+#define MAX_XHLOCK_TRACE_ENTRIES 5
+
+/*
+ * This is for keeping locks waiting for commit so that true dependencies
+ * can be added at commit step.
+ */
+struct hist_lock {
+        /*
+         * Seperate stack_trace data. This will be used at commit step.
+         */
+        struct stack_trace      trace;
+        unsigned long           trace_entries[MAX_XHLOCK_TRACE_ENTRIES];
+
+        /*
+         * Seperate hlock instance. This will be used at commit step.
+         *
+         * TODO: Use a smaller data structure containing only necessary
+         * data. However, we should make lockdep code able to handle the
+         * smaller one first.
+         */
+        struct held_lock        hlock;
+};
+
+/*
+ * To initialize a lock as crosslock, lockdep_init_map_crosslock() should
+ * be called instead of lockdep_init_map().
+ */
+struct cross_lock {
+        /*
+         * Seperate hlock instance. This will be used at commit step.
+         *
+         * TODO: Use a smaller data structure containing only necessary
+         * data. However, we should make lockdep code able to handle the
+         * smaller one first.
+         */
+        struct held_lock        hlock;
 };
 
+struct lockdep_map_cross {
+        struct lockdep_map map;
+        struct cross_lock xlock;
+};
+#endif
+
 /*
  * Initialization, self-test and debugging-output methods:
  */
@@ -282,13 +342,6 @@ extern void lockdep_init_map(struct lockdep_map *lock, const char *name,
                              struct lock_class_key *key, int subclass);
 
 /*
- * To initialize a lockdep_map statically use this macro.
- * Note that _name must not be NULL.
- */
-#define STATIC_LOCKDEP_MAP_INIT(_name, _key) \
-        { .name = (_name), .key = (void *)(_key), }
-
-/*
  * Reinitialize a lock key - for cases where there is special locking or
  * special initialization of locks so that the validator gets the scope
  * of dependencies wrong: they are either too broad (they need a class-split)
@@ -460,6 +513,49 @@ struct pin_cookie { };
 
 #endif /* !LOCKDEP */
 
+enum xhlock_context_t {
+        XHLOCK_HARD,
+        XHLOCK_SOFT,
+        XHLOCK_PROC,
+        XHLOCK_CTX_NR,
+};
+
+#ifdef CONFIG_LOCKDEP_CROSSRELEASE
+extern void lockdep_init_map_crosslock(struct lockdep_map *lock,
+                                       const char *name,
+                                       struct lock_class_key *key,
+                                       int subclass);
+extern void lock_commit_crosslock(struct lockdep_map *lock);
+
+#define STATIC_CROSS_LOCKDEP_MAP_INIT(_name, _key) \
+        { .map.name = (_name), .map.key = (void *)(_key), \
+          .map.cross = 1, }
+
+/*
+ * To initialize a lockdep_map statically use this macro.
+ * Note that _name must not be NULL.
+ */
+#define STATIC_LOCKDEP_MAP_INIT(_name, _key) \
+        { .name = (_name), .key = (void *)(_key), .cross = 0, }
+
+extern void crossrelease_hist_start(enum xhlock_context_t c);
+extern void crossrelease_hist_end(enum xhlock_context_t c);
+extern void lockdep_init_task(struct task_struct *task);
+extern void lockdep_free_task(struct task_struct *task);
+#else
+/*
+ * To initialize a lockdep_map statically use this macro.
+ * Note that _name must not be NULL.
+ */
+#define STATIC_LOCKDEP_MAP_INIT(_name, _key) \
+        { .name = (_name), .key = (void *)(_key), }
+
+static inline void crossrelease_hist_start(enum xhlock_context_t c) {}
+static inline void crossrelease_hist_end(enum xhlock_context_t c) {}
+static inline void lockdep_init_task(struct task_struct *task) {}
+static inline void lockdep_free_task(struct task_struct *task) {}
+#endif
+
 #ifdef CONFIG_LOCK_STAT
 
 extern void lock_contended(struct lockdep_map *lock, unsigned long ip);