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rcu: Annotate SRCU's update-side lockdep dependencies

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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>
This commit is contained in:
Boqun Feng 2023-01-12 22:59:54 -08:00
parent 2f1f043e7b
commit f0f44752f5
3 changed files with 36 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

34
include/linux/srcu.h
View file

@ -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);
}

2
kernel/rcu/srcutiny.c
View file

@ -197,6 +197,8 @@ void synchronize_srcu(struct srcu_struct *ssp)
{
struct rcu_synchronize rs;
srcu_lock_sync(&ssp->dep_map);
RCU_LOCKDEP_WARN(lockdep_is_held(ssp) ||
lock_is_held(&rcu_bh_lock_map) ||
lock_is_held(&rcu_lock_map) ||

2
kernel/rcu/srcutree.c
View file

@ -1307,6 +1307,8 @@ static void __synchronize_srcu(struct srcu_struct *ssp, bool do_norm)
{
struct rcu_synchronize rcu;
srcu_lock_sync(&ssp->dep_map);
RCU_LOCKDEP_WARN(lockdep_is_held(ssp) ||
lock_is_held(&rcu_bh_lock_map) ||
lock_is_held(&rcu_lock_map) ||