diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2023-11-30 14:27:29 +0100 |
|---|---|---|
| committer | Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com> | 2023-12-13 19:11:19 +0100 |
| commit | 3c6b0c1c28184038d90dffe8eb542bedcb8ccf98 (patch) | |
| tree | 3df9369bced39f73c0ea81d163c93c3d8c5ca7d9 /include | |
| parent | srcu: Explain why callbacks invocations can't run concurrently (diff) | |
| download | linux-3c6b0c1c28184038d90dffe8eb542bedcb8ccf98.tar.xz linux-3c6b0c1c28184038d90dffe8eb542bedcb8ccf98.zip | |
srcu: Use try-lock lockdep annotation for NMI-safe access.
It is claimed that srcu_read_lock_nmisafe() NMI-safe. However it
triggers a lockdep if used from NMI because lockdep expects a deadlock
since nothing disables NMIs while the lock is acquired.
This is because commit f0f44752f5f61 ("rcu: Annotate SRCU's update-side
lockdep dependencies") annotates synchronize_srcu() as a write lock
usage. This helps to detect a deadlocks such as
srcu_read_lock();
synchronize_srcu();
srcu_read_unlock();
The side effect is that the lock srcu_struct now has a USED usage in normal
contexts, so it conflicts with a USED_READ usage in NMI. But this shouldn't
cause a real deadlock because the write lock usage from synchronize_srcu()
is a fake one and only used for read/write deadlock detection.
Use a try-lock annotation for srcu_read_lock_nmisafe() to avoid lockdep
complains if used from NMI.
Fixes: f0f44752f5f6 ("rcu: Annotate SRCU's update-side lockdep dependencies")
Link: https://lore.kernel.org/r/20230927160231.XRCDDSK4@linutronix.de
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/rcupdate.h | 6 | ||||
| -rw-r--r-- | include/linux/srcu.h | 2 |
2 files changed, 7 insertions, 1 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index f7206b2623c9..31d523c4e089 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -301,6 +301,11 @@ static inline void rcu_lock_acquire(struct lockdep_map *map) lock_acquire(map, 0, 0, 2, 0, NULL, _THIS_IP_); } +static inline void rcu_try_lock_acquire(struct lockdep_map *map) +{ + lock_acquire(map, 0, 1, 2, 0, NULL, _THIS_IP_); +} + static inline void rcu_lock_release(struct lockdep_map *map) { lock_release(map, _THIS_IP_); @@ -315,6 +320,7 @@ int rcu_read_lock_any_held(void); #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ # define rcu_lock_acquire(a) do { } while (0) +# define rcu_try_lock_acquire(a) do { } while (0) # define rcu_lock_release(a) do { } while (0) static inline int rcu_read_lock_held(void) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 127ef3b2e607..236610e4a8fa 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -229,7 +229,7 @@ static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp srcu_check_nmi_safety(ssp, true); retval = __srcu_read_lock_nmisafe(ssp); - rcu_lock_acquire(&ssp->dep_map); + rcu_try_lock_acquire(&ssp->dep_map); return retval; } |