Messages in this thread Patch in this message | | | From | "Zhang, Qiang" <> | Subject | Question on (locking: Make spinlock_t and rwlock_t a RCU section on RT) | Date | Mon, 26 Jul 2021 07:43:33 +0000 |
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Hello, I have some questions about this patch
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Date: Tue, 19 Nov 2019 09:25:04 +0100 Subject: [PATCH] locking: Make spinlock_t and rwlock_t a RCU section on RT
On !RT a locked spinlock_t and rwlock_t disables preemption which implies a RCU read section. There is code that relies on that behaviour.
Add an explicit RCU read section on RT while a sleeping lock (a lock which would disables preemption on !RT) acquired.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- kernel/locking/rtmutex.c | 6 ++++++ kernel/locking/rwlock-rt.c | 6 ++++++ 2 files changed, 12 insertions(+)
--- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -1136,6 +1136,7 @@ void __lockfunc rt_spin_lock(spinlock_t { spin_acquire(&lock->dep_map, 0, 0, _RET_IP_); rt_spin_lock_fastlock(&lock->lock, rt_spin_lock_slowlock); + rcu_read_lock(); migrate_disable(); ...............................
Operation of sleep is not allowed in RCU read critical area, If after acquiring a rt-spinlock , try to acquire another one rt-spinlock, This may cause sleep, and trigger RCU warning.
Is there a problem with my analysis or something I missed? Thanks Qiang
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