From 808d0387eb7df3f83352ca41f8c943cb3ed61246 Mon Sep 17 00:00:00 2001 From: Colin Cross Date: Wed, 7 Mar 2012 17:34:35 -0800 Subject: [PATCH] staging: android: persistent_ram: make persistent_ram_write atomic Allow persistent_ram_write to be called on multiple cpus at the same time, as long as ecc is not in use. Uses atomics for the buffer->start and buffer->size counters. [jstultz: Fix up some pr_info casting issues on 64bit] CC: Greg KH CC: Android Kernel Team Signed-off-by: Colin Cross Signed-off-by: John Stultz Signed-off-by: Greg Kroah-Hartman --- drivers/staging/android/persistent_ram.c | 140 ++++++++++++++++++++++--------- 1 file changed, 101 insertions(+), 39 deletions(-) diff --git a/drivers/staging/android/persistent_ram.c b/drivers/staging/android/persistent_ram.c index 81950e6..3eb2fb4 100644 --- a/drivers/staging/android/persistent_ram.c +++ b/drivers/staging/android/persistent_ram.c @@ -27,8 +27,8 @@ struct persistent_ram_buffer { uint32_t sig; - uint32_t start; - uint32_t size; + atomic_t start; + atomic_t size; uint8_t data[0]; }; @@ -36,6 +36,66 @@ struct persistent_ram_buffer { static __initdata LIST_HEAD(persistent_ram_list); +static inline size_t buffer_size(struct persistent_ram_zone *prz) +{ + return atomic_read(&prz->buffer->size); +} + +static inline size_t buffer_start(struct persistent_ram_zone *prz) +{ + return atomic_read(&prz->buffer->start); +} + +/* 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) +{ + int old; + int new; + + do { + old = atomic_read(&prz->buffer->start); + new = old + a; + while (unlikely(new > prz->buffer_size)) + new -= prz->buffer_size; + } while (atomic_cmpxchg(&prz->buffer->start, old, new) != old); + + return old; +} + +/* increase the size counter until it hits the max size */ +static inline void buffer_size_add(struct persistent_ram_zone *prz, size_t a) +{ + size_t old; + size_t new; + + if (atomic_read(&prz->buffer->size) == prz->buffer_size) + return; + + do { + old = atomic_read(&prz->buffer->size); + new = old + a; + if (new > prz->buffer_size) + new = prz->buffer_size; + } while (atomic_cmpxchg(&prz->buffer->size, old, new) != old); +} + +/* increase the size counter, retuning an error if it hits the max size */ +static inline ssize_t buffer_size_add_clamp(struct persistent_ram_zone *prz, + size_t a) +{ + size_t old; + size_t new; + + do { + old = atomic_read(&prz->buffer->size); + new = old + a; + if (new > prz->buffer_size) + return -ENOMEM; + } while (atomic_cmpxchg(&prz->buffer->size, old, new) != old); + + return 0; +} + static void persistent_ram_encode_rs8(struct persistent_ram_zone *prz, uint8_t *data, size_t len, uint8_t *ecc) { @@ -62,7 +122,7 @@ static int persistent_ram_decode_rs8(struct persistent_ram_zone *prz, } static void persistent_ram_update_ecc(struct persistent_ram_zone *prz, - unsigned int count) + unsigned int start, unsigned int count) { struct persistent_ram_buffer *buffer = prz->buffer; uint8_t *buffer_end = buffer->data + prz->buffer_size; @@ -75,16 +135,16 @@ static void persistent_ram_update_ecc(struct persistent_ram_zone *prz, if (!prz->ecc) return; - block = buffer->data + (buffer->start & ~(ecc_block_size - 1)); - par = prz->par_buffer + - (buffer->start / ecc_block_size) * prz->ecc_size; + block = buffer->data + (start & ~(ecc_block_size - 1)); + par = prz->par_buffer + (start / ecc_block_size) * prz->ecc_size; + do { if (block + ecc_block_size > buffer_end) size = buffer_end - block; persistent_ram_encode_rs8(prz, block, size, par); block += ecc_block_size; par += ecc_size; - } while (block < buffer->data + buffer->start + count); + } while (block < buffer->data + start + count); } static void persistent_ram_update_header_ecc(struct persistent_ram_zone *prz) @@ -109,7 +169,7 @@ static void persistent_ram_ecc_old(struct persistent_ram_zone *prz) block = buffer->data; par = prz->par_buffer; - while (block < buffer->data + buffer->size) { + while (block < buffer->data + buffer_size(prz)) { int numerr; int size = prz->ecc_block_size; if (block + size > buffer->data + prz->buffer_size) @@ -199,34 +259,33 @@ ssize_t persistent_ram_ecc_string(struct persistent_ram_zone *prz, } static void persistent_ram_update(struct persistent_ram_zone *prz, - const void *s, unsigned int count) + const void *s, unsigned int start, unsigned int count) { struct persistent_ram_buffer *buffer = prz->buffer; - memcpy(buffer->data + buffer->start, s, count); - persistent_ram_update_ecc(prz, count); + memcpy(buffer->data + start, s, count); + persistent_ram_update_ecc(prz, start, count); } static void __init persistent_ram_save_old(struct persistent_ram_zone *prz) { struct persistent_ram_buffer *buffer = prz->buffer; - size_t old_log_size = buffer->size; + size_t size = buffer_size(prz); + size_t start = buffer_start(prz); char *dest; persistent_ram_ecc_old(prz); - dest = kmalloc(old_log_size, GFP_KERNEL); + dest = kmalloc(size, GFP_KERNEL); if (dest == NULL) { pr_err("persistent_ram: failed to allocate buffer\n"); return; } prz->old_log = dest; - prz->old_log_size = old_log_size; - memcpy(prz->old_log, - &buffer->data[buffer->start], buffer->size - buffer->start); - memcpy(prz->old_log + buffer->size - buffer->start, - &buffer->data[0], buffer->start); + prz->old_log_size = size; + memcpy(prz->old_log, &buffer->data[start], size - start); + memcpy(prz->old_log + size - start, &buffer->data[0], start); } int persistent_ram_write(struct persistent_ram_zone *prz, @@ -234,25 +293,26 @@ int persistent_ram_write(struct persistent_ram_zone *prz, { int rem; int c = count; - struct persistent_ram_buffer *buffer = prz->buffer; + size_t start; - if (c > prz->buffer_size) { + if (unlikely(c > prz->buffer_size)) { s += c - prz->buffer_size; c = prz->buffer_size; } - rem = prz->buffer_size - buffer->start; - if (rem < c) { - persistent_ram_update(prz, s, rem); + + buffer_size_add_clamp(prz, c); + + start = buffer_start_add(prz, c); + + rem = prz->buffer_size - start; + if (unlikely(rem < c)) { + persistent_ram_update(prz, s, start, rem); s += rem; c -= rem; - buffer->start = 0; - buffer->size = prz->buffer_size; + start = 0; } - persistent_ram_update(prz, s, c); + persistent_ram_update(prz, s, start, c); - buffer->start += c; - if (buffer->size < prz->buffer_size) - buffer->size += c; persistent_ram_update_header_ecc(prz); return count; @@ -361,23 +421,25 @@ struct persistent_ram_zone *__persistent_ram_init(struct device *dev, bool ecc) return ERR_PTR(ret); if (prz->buffer->sig == PERSISTENT_RAM_SIG) { - if (prz->buffer->size > prz->buffer_size - || prz->buffer->start > prz->buffer->size) - pr_info("persistent_ram: found existing invalid buffer, size %d, start %d\n", - prz->buffer->size, prz->buffer->start); + if (buffer_size(prz) > prz->buffer_size || + buffer_start(prz) > buffer_size(prz)) + pr_info("persistent_ram: found existing invalid buffer," + " size %ld, start %ld\n", + buffer_size(prz), buffer_start(prz)); else { - pr_info("persistent_ram: found existing buffer, size %d, start %d\n", - prz->buffer->size, prz->buffer->start); + pr_info("persistent_ram: found existing buffer," + " size %ld, start %ld\n", + buffer_size(prz), buffer_start(prz)); persistent_ram_save_old(prz); } } else { - pr_info("persistent_ram: no valid data in buffer (sig = 0x%08x)\n", - prz->buffer->sig); + pr_info("persistent_ram: no valid data in buffer" + " (sig = 0x%08x)\n", prz->buffer->sig); } prz->buffer->sig = PERSISTENT_RAM_SIG; - prz->buffer->start = 0; - prz->buffer->size = 0; + atomic_set(&prz->buffer->start, 0); + atomic_set(&prz->buffer->size, 0); return prz; } -- 2.7.4