[tip:locking/core] locking/lockdep: Add a function building a chain between two classes

[tip-bot for Byungchul Park]

Commit-ID:  49347a986ab45eb1dafbf25170647c890f8ff192
Gitweb: http://git.kernel.org/tip/49347a986ab45eb1dafbf25170647c890f8ff192
Author: Byungchul Park 
AuthorDate: Mon, 7 Aug 2017 16:12:49 +0900
Committer:  Ingo Molnar 
CommitDate: Thu, 10 Aug 2017 12:29:05 +0200

locking/lockdep: Add a function building a chain between two classes

Crossrelease needs to build a chain between two classes regardless of
their contexts. However, add_chain_cache() cannot be used for that
purpose since it assumes that it's called in the acquisition context
of the hlock. So this patch introduces a new function doing it.

Signed-off-by: Byungchul Park 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: a...@linux-foundation.org
Cc: boqun.f...@gmail.com
Cc: kernel-t...@lge.com
Cc: kir...@shutemov.name
Cc: npig...@gmail.com
Cc: wal...@google.com
Cc: wi...@infradead.org
Link: 
http://lkml.kernel.org/r/1502089981-21272-3-git-send-email-byungchul.p...@lge.com
Signed-off-by: Ingo Molnar 
---
 kernel/locking/lockdep.c | 70 
 1 file changed, 70 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index e029f2f..bdf6b31 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2151,6 +2151,76 @@ static int check_no_collision(struct task_struct *curr,
 }
 
 /*
+ * This is for building a chain between just two different classes,
+ * instead of adding a new hlock upon current, which is done by
+ * add_chain_cache().
+ *
+ * This can be called in any context with two classes, while
+ * add_chain_cache() must be done within the lock owener's context
+ * since it uses hlock which might be racy in another context.
+ */
+static inline int add_chain_cache_classes(unsigned int prev,
+ unsigned int next,
+ unsigned int irq_context,
+ u64 chain_key)
+{
+   struct hlist_head *hash_head = chainhashentry(chain_key);
+   struct lock_chain *chain;
+
+   /*
+* Allocate a new chain entry from the static array, and add
+* it to the hash:
+*/
+
+   /*
+* We might need to take the graph lock, ensure we've got IRQs
+* disabled to make this an IRQ-safe lock.. for recursion reasons
+* lockdep won't complain about its own locking errors.
+*/
+   if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+   return 0;
+
+   if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
+   if (!debug_locks_off_graph_unlock())
+   return 0;
+
+   print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
+   dump_stack();
+   return 0;
+   }
+
+   chain = lock_chains + nr_lock_chains++;
+   chain->chain_key = chain_key;
+   chain->irq_context = irq_context;
+   chain->depth = 2;
+   if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) 
{
+   chain->base = nr_chain_hlocks;
+   nr_chain_hlocks += chain->depth;
+   chain_hlocks[chain->base] = prev - 1;
+   chain_hlocks[chain->base + 1] = next -1;
+   }
+#ifdef CONFIG_DEBUG_LOCKDEP
+   /*
+* Important for check_no_collision().
+*/
+   else {
+   if (!debug_locks_off_graph_unlock())
+   return 0;
+
+   print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
+   dump_stack();
+   return 0;
+   }
+#endif
+
+   hlist_add_head_rcu(>entry, hash_head);
+   debug_atomic_inc(chain_lookup_misses);
+   inc_chains();
+
+   return 1;
+}
+
+/*
  * Adds a dependency chain into chain hashtable. And must be called with
  * graph_lock held.
  *

[tip:locking/core] locking/lockdep: Add a function building a chain between two classes

[tip-bot for Byungchul Park]

Commit-ID:  49347a986ab45eb1dafbf25170647c890f8ff192
Gitweb: http://git.kernel.org/tip/49347a986ab45eb1dafbf25170647c890f8ff192
Author: Byungchul Park 
AuthorDate: Mon, 7 Aug 2017 16:12:49 +0900
Committer:  Ingo Molnar 
CommitDate: Thu, 10 Aug 2017 12:29:05 +0200

locking/lockdep: Add a function building a chain between two classes

Crossrelease needs to build a chain between two classes regardless of
their contexts. However, add_chain_cache() cannot be used for that
purpose since it assumes that it's called in the acquisition context
of the hlock. So this patch introduces a new function doing it.

Signed-off-by: Byungchul Park 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: a...@linux-foundation.org
Cc: boqun.f...@gmail.com
Cc: kernel-t...@lge.com
Cc: kir...@shutemov.name
Cc: npig...@gmail.com
Cc: wal...@google.com
Cc: wi...@infradead.org
Link: 
http://lkml.kernel.org/r/1502089981-21272-3-git-send-email-byungchul.p...@lge.com
Signed-off-by: Ingo Molnar 
---
 kernel/locking/lockdep.c | 70 
 1 file changed, 70 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index e029f2f..bdf6b31 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2151,6 +2151,76 @@ static int check_no_collision(struct task_struct *curr,
 }
 
 /*
+ * This is for building a chain between just two different classes,
+ * instead of adding a new hlock upon current, which is done by
+ * add_chain_cache().
+ *
+ * This can be called in any context with two classes, while
+ * add_chain_cache() must be done within the lock owener's context
+ * since it uses hlock which might be racy in another context.
+ */
+static inline int add_chain_cache_classes(unsigned int prev,
+ unsigned int next,
+ unsigned int irq_context,
+ u64 chain_key)
+{
+   struct hlist_head *hash_head = chainhashentry(chain_key);
+   struct lock_chain *chain;
+
+   /*
+* Allocate a new chain entry from the static array, and add
+* it to the hash:
+*/
+
+   /*
+* We might need to take the graph lock, ensure we've got IRQs
+* disabled to make this an IRQ-safe lock.. for recursion reasons
+* lockdep won't complain about its own locking errors.
+*/
+   if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+   return 0;
+
+   if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
+   if (!debug_locks_off_graph_unlock())
+   return 0;
+
+   print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
+   dump_stack();
+   return 0;
+   }
+
+   chain = lock_chains + nr_lock_chains++;
+   chain->chain_key = chain_key;
+   chain->irq_context = irq_context;
+   chain->depth = 2;
+   if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) 
{
+   chain->base = nr_chain_hlocks;
+   nr_chain_hlocks += chain->depth;
+   chain_hlocks[chain->base] = prev - 1;
+   chain_hlocks[chain->base + 1] = next -1;
+   }
+#ifdef CONFIG_DEBUG_LOCKDEP
+   /*
+* Important for check_no_collision().
+*/
+   else {
+   if (!debug_locks_off_graph_unlock())
+   return 0;
+
+   print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
+   dump_stack();
+   return 0;
+   }
+#endif
+
+   hlist_add_head_rcu(>entry, hash_head);
+   debug_atomic_inc(chain_lookup_misses);
+   inc_chains();
+
+   return 1;
+}
+
+/*
  * Adds a dependency chain into chain hashtable. And must be called with
  * graph_lock held.
  *