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locking fixes

GIT PULL Merged Ingo Molnar 2 participants 2 messages Jan 18, 2020 Locking primitives

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Ingo Molnar

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Linus,

Please pull the latest locking-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-for-linus

# HEAD: 39e7234f00bc93613c086ae42d852d5f4147120a locking/rwsem: Fix kernel crash when spinning on RWSEM_OWNER_UNKNOWN

Three fixes:

- Fix an rwsem spin-on-owner crash, introduced in v5.4
- Fix a lockdep bug when running out of stack_trace entries, introduced in v5.4
- Docbook fix

Thanks,

Ingo

------------------>
Randy Dunlap (1):
futex: Fix kernel-doc notation warning

Waiman Long (2):
locking/lockdep: Fix buffer overrun problem in stack_trace[] locking/rwsem: Fix kernel crash when spinning on RWSEM_OWNER_UNKNOWN

 kernel/futex.c           | 1 +
 kernel/locking/lockdep.c | 7 +++----
 kernel/locking/rwsem.c   | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)
kernel/futex.c +1 -0
index 03c518e9747e..0cf84c8664f2 100644
@@ -1178,6 +1178,7 @@ static int attach_to_pi_state(u32 __user *uaddr, u32 uval,
 
 /**
  * wait_for_owner_exiting - Block until the owner has exited
+ * @ret: owner's current futex lock status
  * @exiting:	Pointer to the exiting task
  *
  * Caller must hold a refcount on @exiting.
kernel/locking/lockdep.c +3 -4
index 32282e7112d3..32406ef0d6a2 100644
@@ -482,7 +482,7 @@ static struct lock_trace *save_trace(void)
 	struct lock_trace *trace, *t2;
 	struct hlist_head *hash_head;
 	u32 hash;
-	unsigned int max_entries;
+	int max_entries;
 
 	BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
 	BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);

@@ -490,10 +490,8 @@ static struct lock_trace *save_trace(void)
 	trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
 	max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
 		LOCK_TRACE_SIZE_IN_LONGS;
-	trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
 
-	if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES -
-	    LOCK_TRACE_SIZE_IN_LONGS - 1) {
+	if (max_entries <= 0) {
 		if (!debug_locks_off_graph_unlock())
 			return NULL;
 

@@ -502,6 +500,7 @@ static struct lock_trace *save_trace(void)
 
 		return NULL;
 	}
+	trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
 
 	hash = jhash(trace->entries, trace->nr_entries *
 		     sizeof(trace->entries[0]), 0);
kernel/locking/rwsem.c +2 -2
index 44e68761f432..0d9b6be9ecc8 100644
@@ -1226,8 +1226,8 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state)
 		 * In this case, we attempt to acquire the lock again
 		 * without sleeping.
 		 */
-		if ((wstate == WRITER_HANDOFF) &&
-		    (rwsem_spin_on_owner(sem, 0) == OWNER_NULL))
+		if (wstate == WRITER_HANDOFF &&
+		    rwsem_spin_on_owner(sem, RWSEM_NONSPINNABLE) == OWNER_NULL)
 			goto trylock_again;
 
 		/* Block until there are no active lockers. */
merge bot Merged
#1 lore raw
The pull request you sent on Sat, 18 Jan 2020 18:53:09 +0100:

The pull request you sent on Sat, 18 Jan 2020 18:53:09 +0100:

Quoted 1 line

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-for-linus

has been merged into torvalds/linux.git:
https://git.kernel.org/torvalds/c/124b5547ec1e1c935c5cc3dfe9f3c04669ecb5e4

Thank you!

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