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authorBoqun Feng <boqun.feng@gmail.com>2023-01-13 09:59:54 +0300
committerBoqun Feng <boqun.feng@gmail.com>2023-03-27 21:15:59 +0300
commitf0f44752f5f61ee4e3bd88ae033fdb888320aafe (patch)
tree0cbab17b4ff02f74ba556e295f1763bef09a2498 /include/linux/srcu.h
parent2f1f043e7bea3fbf4c1869df2f7a0312bc8ca2bf (diff)
downloadlinux-f0f44752f5f61ee4e3bd88ae033fdb888320aafe.tar.xz
rcu: Annotate SRCU's update-side lockdep dependencies
Although all flavors of RCU readers are annotated correctly with lockdep as recursive read locks, they do not set the lock_acquire 'check' parameter. This means that RCU read locks are not added to the lockdep dependency graph, which in turn means that lockdep cannot detect RCU-based deadlocks. This is not a problem for RCU flavors having atomic read-side critical sections because context-based annotations can catch these deadlocks, see for example the RCU_LOCKDEP_WARN() statement in synchronize_rcu(). But context-based annotations are not helpful for sleepable RCU, especially given that it is perfectly legal to do synchronize_srcu(&srcu1) within an srcu_read_lock(&srcu2). However, we can detect SRCU-based by: (1) Making srcu_read_lock() a 'check'ed recursive read lock and (2) Making synchronize_srcu() a empty write lock critical section. Even better, with the newly introduced lock_sync(), we can avoid false positives about irq-unsafe/safe. This commit therefore makes it so. Note that NMI-safe SRCU read side critical sections are currently not annotated, but might be annotated in the future. Signed-off-by: Boqun Feng <boqun.feng@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> [ boqun: Add comments for annotation per Waiman's suggestion ] [ boqun: Fix comment warning reported by Stephen Rothwell ] Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Diffstat (limited to 'include/linux/srcu.h')
-rw-r--r--include/linux/srcu.h34
1 files changed, 32 insertions, 2 deletions
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 74796cd7e7a9..41c4b26fb1c1 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -102,6 +102,32 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
return lock_is_held(&ssp->dep_map);
}
+/*
+ * Annotations provide deadlock detection for SRCU.
+ *
+ * Similar to other lockdep annotations, except there is an additional
+ * srcu_lock_sync(), which is basically an empty *write*-side critical section,
+ * see lock_sync() for more information.
+ */
+
+/* Annotates a srcu_read_lock() */
+static inline void srcu_lock_acquire(struct lockdep_map *map)
+{
+ lock_map_acquire_read(map);
+}
+
+/* Annotates a srcu_read_lock() */
+static inline void srcu_lock_release(struct lockdep_map *map)
+{
+ lock_map_release(map);
+}
+
+/* Annotates a synchronize_srcu() */
+static inline void srcu_lock_sync(struct lockdep_map *map)
+{
+ lock_map_sync(map);
+}
+
#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
@@ -109,6 +135,10 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
return 1;
}
+#define srcu_lock_acquire(m) do { } while (0)
+#define srcu_lock_release(m) do { } while (0)
+#define srcu_lock_sync(m) do { } while (0)
+
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
#define SRCU_NMI_UNKNOWN 0x0
@@ -182,7 +212,7 @@ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
srcu_check_nmi_safety(ssp, false);
retval = __srcu_read_lock(ssp);
- rcu_lock_acquire(&(ssp)->dep_map);
+ srcu_lock_acquire(&(ssp)->dep_map);
return retval;
}
@@ -254,7 +284,7 @@ static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx)
{
WARN_ON_ONCE(idx & ~0x1);
srcu_check_nmi_safety(ssp, false);
- rcu_lock_release(&(ssp)->dep_map);
+ srcu_lock_release(&(ssp)->dep_map);
__srcu_read_unlock(ssp, idx);
}