On 1/7/25 8:59 AM, Kumar Kartikeya Dwivedi wrote:
Introduce helper macros that wrap around the rqspinlock slow path and
provide an interface analogous to the raw_spin_lock API. Note that
in case of error conditions, preemption and IRQ disabling is
automatically unrolled before returning the error back to the caller.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
---
include/asm-generic/rqspinlock.h | 58 ++++++++++++++++++++++++++++++++
1 file changed, 58 insertions(+)
diff --git a/include/asm-generic/rqspinlock.h b/include/asm-generic/rqspinlock.h
index dc436ab01471..53be8426373c 100644
--- a/include/asm-generic/rqspinlock.h
+++ b/include/asm-generic/rqspinlock.h
@@ -12,8 +12,10 @@
#include <linux/types.h>
#include <vdso/time64.h>
#include <linux/percpu.h>
+#include <asm/qspinlock.h>
struct qspinlock;
+typedef struct qspinlock rqspinlock_t;
extern int resilient_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val, u64 timeout);
@@ -82,4 +84,60 @@ static __always_inline void release_held_lock_entry(void)
this_cpu_dec(rqspinlock_held_locks.cnt);
}
+/**
+ * res_spin_lock - acquire a queued spinlock
+ * @lock: Pointer to queued spinlock structure
+ */
+static __always_inline int res_spin_lock(rqspinlock_t *lock)
+{
+ int val = 0;
+
+ if (likely(atomic_try_cmpxchg_acquire(&lock->val, &val, _Q_LOCKED_VAL))) {
+ grab_held_lock_entry(lock);
+ return 0;
+ }
+ return resilient_queued_spin_lock_slowpath(lock, val, RES_DEF_TIMEOUT);
+}
+
+static __always_inline void res_spin_unlock(rqspinlock_t *lock)
+{
+ struct rqspinlock_held *rqh = this_cpu_ptr(&rqspinlock_held_locks);
+
+ if (unlikely(rqh->cnt > RES_NR_HELD))
+ goto unlock;
+ WRITE_ONCE(rqh->locks[rqh->cnt - 1], NULL);
+ /*
+ * Release barrier, ensuring ordering. See release_held_lock_entry.
+ */
+unlock:
+ queued_spin_unlock(lock);
+ this_cpu_dec(rqspinlock_held_locks.cnt);
+}
+
+#define raw_res_spin_lock_init(lock) ({ *(lock) = (struct qspinlock)__ARCH_SPIN_LOCK_UNLOCKED; })
+
+#define raw_res_spin_lock(lock) \
+ ({ \
+ int __ret; \
+ preempt_disable(); \
+ __ret = res_spin_lock(lock); \
+ if (__ret) \
+ preempt_enable(); \
+ __ret; \
+ })
+
+#define raw_res_spin_unlock(lock) ({ res_spin_unlock(lock); preempt_enable(); })
+
+#define raw_res_spin_lock_irqsave(lock, flags) \
+ ({ \
+ int __ret; \
+ local_irq_save(flags); \
+ __ret = raw_res_spin_lock(lock); \
+ if (__ret) \
+ local_irq_restore(flags); \
+ __ret; \
+ })
+
+#define raw_res_spin_unlock_irqrestore(lock, flags) ({ raw_res_spin_unlock(lock); local_irq_restore(flags); })
+
#endif /* __ASM_GENERIC_RQSPINLOCK_H */
Lockdep calls aren't included in the helper functions. That means all
the *res_spin_lock*() calls will be outside the purview of lockdep. That
also means a multi-CPU circular locking dependency involving a mixture
of qspinlocks and rqspinlocks may not be detectable.
Cheers,
Longman
