lkml.org 
[lkml]   [2012]   [Mar]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 08/11] android: persistent_ram: make persistent_ram_write atomic
    Date
    From: Colin Cross <ccross@android.com>

    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 <gregkh@linuxfoundation.org>
    CC: Android Kernel Team <kernel-team@android.com>
    Signed-off-by: Colin Cross <ccross@android.com>
    Signed-off-by: John Stultz <john.stultz@linaro.org>
    ---
    drivers/staging/android/persistent_ram.c | 140 +++++++++++++++++++++--------
    1 files 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;
    }
    --
    1.7.3.2.146.gca209


    \
     
     \ /
      Last update: 2012-03-08 02:39    [W:0.035 / U:31.108 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site