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author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2023-11-30 16:27:29 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-01-26 02:35:49 +0300 |
commit | ac0de86fa7f51d19956950e45d0a62a3d193cd08 (patch) | |
tree | b76ee3bec3b96cc87c8149da4420d303a0308e69 | |
parent | fa1a1bad0f1c913531c325cba2a5a8faaa4e6a50 (diff) | |
download | linux-ac0de86fa7f51d19956950e45d0a62a3d193cd08.tar.xz |
srcu: Use try-lock lockdep annotation for NMI-safe access.
[ Upstream commit 3c6b0c1c28184038d90dffe8eb542bedcb8ccf98 ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
-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 5e5f920ade90..44aab5c0bd2c 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -303,6 +303,11 @@ 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_); @@ -317,6 +322,7 @@ 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; } |