Module Name: src
Committed By: riastradh
Date: Sun Dec 19 01:21:30 UTC 2021
Modified Files:
src/sys/external/bsd/drm2/include/linux: seqlock.h
Log Message:
Revamp seqlock. Fix some stupid bugs. Add seqcount.
To generate a diff of this commit:
cvs rdiff -u -r1.2 -r1.3 src/sys/external/bsd/drm2/include/linux/seqlock.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/external/bsd/drm2/include/linux/seqlock.h
diff -u src/sys/external/bsd/drm2/include/linux/seqlock.h:1.2 src/sys/external/bsd/drm2/include/linux/seqlock.h:1.3
--- src/sys/external/bsd/drm2/include/linux/seqlock.h:1.2 Sun Dec 19 00:47:40 2021
+++ src/sys/external/bsd/drm2/include/linux/seqlock.h Sun Dec 19 01:21:30 2021
@@ -1,4 +1,4 @@
-/* $NetBSD: seqlock.h,v 1.2 2021/12/19 00:47:40 riastradh Exp $ */
+/* $NetBSD: seqlock.h,v 1.3 2021/12/19 01:21:30 riastradh Exp $ */
/*-
* Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -38,8 +38,88 @@
#include <lib/libkern/libkern.h>
+struct seqcount {
+ unsigned sqc_gen;
+};
+
+typedef struct seqcount seqcount_t;
+
+static inline void
+seqcount_init(struct seqcount *seqcount)
+{
+
+ seqcount->sqc_gen = 0;
+}
+
+static inline void
+seqcount_destroy(struct seqcount *seqcount)
+{
+
+ KASSERT((seqcount->sqc_gen & 1) == 0);
+ seqcount->sqc_gen = -1;
+}
+
+static inline void
+write_seqcount_begin(struct seqcount *seqcount)
+{
+
+ KASSERT((seqcount->sqc_gen & 1) == 0);
+ seqcount->sqc_gen |= 1;
+ membar_producer();
+}
+
+static inline void
+write_seqcount_end(struct seqcount *seqcount)
+{
+
+ KASSERT((seqcount->sqc_gen & 1) == 1);
+ membar_producer();
+ seqcount->sqc_gen |= 1; /* paranoia */
+ seqcount->sqc_gen++;
+}
+
+static inline unsigned
+__read_seqcount_begin(struct seqcount *seqcount)
+{
+ unsigned gen;
+
+ while (__predict_false((gen = seqcount->sqc_gen) & 1))
+ SPINLOCK_BACKOFF_HOOK;
+ __insn_barrier();
+
+ return gen;
+}
+
+static inline bool
+__read_seqcount_retry(struct seqcount *seqcount, unsigned gen)
+{
+
+ __insn_barrier();
+ return __predict_false(seqcount->sqc_gen != gen);
+}
+
+static inline unsigned
+read_seqcount_begin(struct seqcount *seqcount)
+{
+ unsigned gen;
+
+ gen = __read_seqcount_begin(seqcount);
+ membar_consumer();
+
+ return gen;
+}
+
+static inline bool
+read_seqcount_retry(struct seqcount *seqcount, unsigned gen)
+{
+
+ membar_consumer();
+ return __read_seqcount_retry(seqcount, gen);
+}
+
struct seqlock {
- uint64_t sql_gen;
+ kmutex_t sql_lock;
+ struct seqcount sql_count;
};
typedef struct seqlock seqlock_t;
@@ -48,26 +128,32 @@ static inline void
seqlock_init(struct seqlock *seqlock)
{
- seqlock->sql_gen = 0;
+ mutex_init(&seqlock->sql_lock, MUTEX_DEFAULT, IPL_VM);
+ seqcount_init(&seqlock->sql_count);
+}
+
+static inline void
+seqlock_destroy(struct seqlock *seqlock)
+{
+
+ seqcount_destroy(&seqlock->sql_count);
+ mutex_destroy(&seqlock->sql_lock);
}
static inline void
write_seqlock(struct seqlock *seqlock)
{
- KASSERT((seqlock->sql_gen & 1) == 0);
- seqlock->sql_gen |= 1;
- membar_producer();
+ mutex_spin_enter(&seqlock->sql_lock);
+ write_seqcount_begin(&seqlock->sql_count);
}
static inline void
write_sequnlock(struct seqlock *seqlock)
{
- KASSERT((seqlock->sql_gen & 1) == 1);
- membar_producer();
- seqlock->sql_gen |= 1; /* paraonia */
- seqlock->sql_gen++;
+ write_seqcount_end(&seqlock->sql_count);
+ mutex_spin_exit(&seqlock->sql_lock);
}
#define write_seqlock_irqsave(SEQLOCK, FLAGS) do { \
@@ -76,27 +162,22 @@ write_sequnlock(struct seqlock *seqlock)
} while (0)
#define write_sequnlock_irqrestore(SEQLOCK, FLAGS) do { \
- write_seqlock(SEQLOCK); \
+ write_sequnlock(SEQLOCK); \
splx((int)(FLAGS)); \
} while (0)
-static inline uint64_t
+static inline unsigned
read_seqbegin(struct seqlock *seqlock)
{
- uint64_t gen;
- while ((gen = seqlock->sql_gen) & 1)
- SPINLOCK_BACKOFF_HOOK;
- membar_consumer();
-
- return gen;
+ return read_seqcount_begin(&seqlock->sql_count);
}
static inline bool
-read_seqretry(struct seqlock *seqlock, uint64_t gen)
+read_seqretry(struct seqlock *seqlock, unsigned gen)
{
- return gen != seqlock->sql_gen;
+ return read_seqcount_retry(&seqlock->sql_count, gen);
}
#endif /* _LINUX_SEQLOCK_H_ */
