Commit 0405a5ce authored by Rob Herring's avatar Rob Herring Committed by Tony Luck
Browse files

pstore/ram: avoid atomic accesses for ioremapped regions 



For persistent RAM outside of main memory, the memory may have limitations
on supported accesses. For internal RAM on highbank platform exclusive
accesses are not supported and will hang the system. So atomic_cmpxchg
cannot be used. This commit uses spinlock protection for buffer size and
start updates on ioremapped regions instead.

Signed-off-by: default avatarRob Herring <rob.herring@calxeda.com>
Acked-by: default avatarAnton Vorontsov <anton@enomsg.org>
Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
parent 77418921

fs/pstore/ram_core.c

+52 −2
Original line number Diff line number Diff line
@@ -46,7 +46,7 @@ static inline size_t buffer_start(struct persistent_ram_zone *prz) 
}



/* increase and wrap the start pointer, returning the old value */

static inline size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a)

static size_t buffer_start_add_atomic(struct persistent_ram_zone *prz, size_t a)

{

	int old;

	int new;
@@ -62,7 +62,7 @@ static inline size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a) 
}



/* increase the size counter until it hits the max size */

static inline void buffer_size_add(struct persistent_ram_zone *prz, size_t a)

static void buffer_size_add_atomic(struct persistent_ram_zone *prz, size_t a)

{

	size_t old;

	size_t new;
@@ -78,6 +78,53 @@ static inline void buffer_size_add(struct persistent_ram_zone *prz, size_t a) 
	} while (atomic_cmpxchg(&prz->buffer->size, old, new) != old);

}



static DEFINE_RAW_SPINLOCK(buffer_lock);



/* increase and wrap the start pointer, returning the old value */

static size_t buffer_start_add_locked(struct persistent_ram_zone *prz, size_t a)

{

	int old;

	int new;

	unsigned long flags;



	raw_spin_lock_irqsave(&buffer_lock, flags);



	old = atomic_read(&prz->buffer->start);

	new = old + a;

	while (unlikely(new > prz->buffer_size))

		new -= prz->buffer_size;

	atomic_set(&prz->buffer->start, new);



	raw_spin_unlock_irqrestore(&buffer_lock, flags);



	return old;

}



/* increase the size counter until it hits the max size */

static void buffer_size_add_locked(struct persistent_ram_zone *prz, size_t a)

{

	size_t old;

	size_t new;

	unsigned long flags;



	raw_spin_lock_irqsave(&buffer_lock, flags);



	old = atomic_read(&prz->buffer->size);

	if (old == prz->buffer_size)

		goto exit;



	new = old + a;

	if (new > prz->buffer_size)

		new = prz->buffer_size;

	atomic_set(&prz->buffer->size, new);



exit:

	raw_spin_unlock_irqrestore(&buffer_lock, flags);

}



static size_t (*buffer_start_add)(struct persistent_ram_zone *, size_t) = buffer_start_add_atomic;

static void (*buffer_size_add)(struct persistent_ram_zone *, size_t) = buffer_size_add_atomic;



static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz,

	uint8_t *data, size_t len, uint8_t *ecc)

{
@@ -372,6 +419,9 @@ static void *persistent_ram_iomap(phys_addr_t start, size_t size) 
		return NULL;

	}



	buffer_start_add = buffer_start_add_locked;

	buffer_size_add = buffer_size_add_locked;



	return ioremap(start, size);

}

CRA Git | Maintained and supported by SUSTech CRA and CCSE