Messages in this thread Patch in this message | | | Date | Sat, 28 Aug 2021 01:21:46 +0800 | From | Boqun Feng <> | Subject | Re: [patch V5 32/72] locking/rtmutex: Provide the spin/rwlock core lock function |
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On Sun, Aug 15, 2021 at 11:28:25PM +0200, Thomas Gleixner wrote: > From: Thomas Gleixner <tglx@linutronix.de> > > A simplified version of the rtmutex slowlock function which neither handles > signals nor timeouts and is careful about preserving the state of the > blocked task across the lock operation. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > --- > kernel/locking/rtmutex.c | 60 ++++++++++++++++++++++++++++++++++++++++ > kernel/locking/rtmutex_common.h | 2 - > 2 files changed, 61 insertions(+), 1 deletion(-) > --- > --- a/kernel/locking/rtmutex.c > +++ b/kernel/locking/rtmutex.c > @@ -1416,3 +1416,63 @@ static __always_inline int __rt_mutex_lo > return rt_mutex_slowlock(lock, state); > } > #endif /* RT_MUTEX_BUILD_MUTEX */ > + > +#ifdef RT_MUTEX_BUILD_SPINLOCKS > +/* > + * Functions required for spin/rw_lock substitution on RT kernels > + */ > + > +/** > + * rtlock_slowlock_locked - Slow path lock acquisition for RT locks > + * @lock: The underlying rt mutex > + */ > +static void __sched rtlock_slowlock_locked(struct rt_mutex_base *lock) > +{ > + struct rt_mutex_waiter waiter; > + > + lockdep_assert_held(&lock->wait_lock); > + > + if (try_to_take_rt_mutex(lock, current, NULL)) > + return; > + > + rt_mutex_init_rtlock_waiter(&waiter); > + > + /* Save current state and set state to TASK_RTLOCK_WAIT */ > + current_save_and_set_rtlock_wait_state(); > + > + task_blocks_on_rt_mutex(lock, &waiter, current, RT_MUTEX_MIN_CHAINWALK); > + > + for (;;) { > + /* Try to acquire the lock again. */ > + if (try_to_take_rt_mutex(lock, current, &waiter)) > + break; > + > + raw_spin_unlock_irq(&lock->wait_lock); > + > + schedule_rtlock(); > + > + raw_spin_lock_irq(&lock->wait_lock); > + set_current_state(TASK_RTLOCK_WAIT); > + } > + > + /* Restore the task state */ > + current_restore_rtlock_saved_state(); > + > + /* > + * try_to_take_rt_mutex() sets the waiter bit unconditionally. We > + * might have to fix that up: > + */ > + fixup_rt_mutex_waiters(lock); > + debug_rt_mutex_free_waiter(&waiter); > +} > + > +static __always_inline void __sched rtlock_slowlock(struct rt_mutex_base *lock) > +{ > + unsigned long flags; > + > + raw_spin_lock_irqsave(&lock->wait_lock, flags); > + rtlock_slowlock_locked(lock); > + raw_spin_unlock_irqrestore(&lock->wait_lock, flags);
Just out of curiosity, could we use raw_spin_{un,}lock_irq() here instead of *_irq{save,restore}()? Because rtlock_slowlock() might sleep, and we cannot call it with irq-off.
Regards, Boqun
> +} > + > +#endif /* RT_MUTEX_BUILD_SPINLOCKS */ > --- a/kernel/locking/rtmutex_common.h > +++ b/kernel/locking/rtmutex_common.h > @@ -181,7 +181,7 @@ static inline void rt_mutex_init_waiter( > waiter->task = NULL; > } > > -static inline void rtlock_init_rtmutex_waiter(struct rt_mutex_waiter *waiter) > +static inline void rt_mutex_init_rtlock_waiter(struct rt_mutex_waiter *waiter) > { > rt_mutex_init_waiter(waiter); > waiter->wake_state = TASK_RTLOCK_WAIT; >
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