Commit 639a2b25 authored by Stephen Hemminger's avatar Stephen Hemminger Committed by Linus Torvalds

[PATCH] monotonic seqlock for cyclone timer

Replace read/write lock used for cyclone timer monotonic_lock with seqlock.
Similar to locking used on xtime and monotonic_lock in timers/timer_tsc.c
parent 70f6d49e
......@@ -35,7 +35,7 @@ static u32* volatile cyclone_timer; /* Cyclone MPMC0 register */
static u32 last_cyclone_low;
static u32 last_cyclone_high;
static unsigned long long monotonic_base;
static rwlock_t monotonic_lock = RW_LOCK_UNLOCKED;
static seqlock_t monotonic_lock = SEQLOCK_UNLOCKED;
/* helper macro to atomically read both cyclone counter registers */
#define read_cyclone_counter(low,high) \
......@@ -51,7 +51,7 @@ static void mark_offset_cyclone(void)
int count;
unsigned long long this_offset, last_offset;
write_lock(&monotonic_lock);
write_seqlock(&monotonic_lock);
last_offset = ((unsigned long long)last_cyclone_high<<32)|last_cyclone_low;
spin_lock(&i8253_lock);
......@@ -76,7 +76,7 @@ static void mark_offset_cyclone(void)
/* update the monotonic base value */
this_offset = ((unsigned long long)last_cyclone_high<<32)|last_cyclone_low;
monotonic_base += (this_offset - last_offset) & CYCLONE_TIMER_MASK;
write_unlock(&monotonic_lock);
write_sequnlock(&monotonic_lock);
/* calculate delay_at_last_interrupt */
count = ((LATCH-1) - count) * TICK_SIZE;
......@@ -117,12 +117,15 @@ static unsigned long long monotonic_clock_cyclone(void)
u32 now_low, now_high;
unsigned long long last_offset, this_offset, base;
unsigned long long ret;
unsigned seq;
/* atomically read monotonic base & last_offset */
read_lock_irq(&monotonic_lock);
do {
seq = read_seqbegin(&monotonic_lock);
last_offset = ((unsigned long long)last_cyclone_high<<32)|last_cyclone_low;
base = monotonic_base;
read_unlock_irq(&monotonic_lock);
} while (read_seqretry(&monotonic_lock, seq));
/* Read the cyclone counter */
read_cyclone_counter(now_low,now_high);
......
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