Messages in this thread | | | Date | Thu, 8 Sep 2016 14:32:05 -0700 | From | Guenter Roeck <> | Subject | Re: pstore/core: drop cmpxchg based updates |
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On Wed, Aug 24, 2016 at 03:09:35PM +0200, Sebastian Andrzej Siewior wrote: > I have here a FPGA behind PCIe which exports SRAM which I use for > pstore. Now it seems that the FPGA no longer supports cmpxchg based > updates and writes back 0xff…ff and returns the same. This leads to > crash during crash rendering pstore useless. > Since I doubt that there is much benefit from using cmpxchg() here, I am > dropping this atomic access and use the spinlock based version. > > Cc: Anton Vorontsov <anton@enomsg.org> > Cc: Colin Cross <ccross@android.com> > Cc: Kees Cook <keescook@chromium.org> > Cc: Tony Luck <tony.luck@intel.com> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > Tested-by: Rabin Vincent <rabinv@axis.com>
Great, one item taken off my task list.
As Rabin suggested, this patch is needed for at least some ARM chips, and should be applied to stable releases.
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
> --- > fs/pstore/ram_core.c | 43 ++----------------------------------------- > 1 file changed, 2 insertions(+), 41 deletions(-) > > diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c > index 76c3f80efdfa..4bae54bb61cd 100644 > --- a/fs/pstore/ram_core.c > +++ b/fs/pstore/ram_core.c > @@ -47,39 +47,6 @@ 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 size_t buffer_start_add_atomic(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 void buffer_size_add_atomic(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); > -} > - > static DEFINE_RAW_SPINLOCK(buffer_lock); > > /* increase and wrap the start pointer, returning the old value */ > @@ -124,9 +91,6 @@ static void buffer_size_add_locked(struct persistent_ram_zone *prz, size_t a) > 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) > { > @@ -338,9 +302,9 @@ int notrace persistent_ram_write(struct persistent_ram_zone *prz, > c = prz->buffer_size; > } > > - buffer_size_add(prz, c); > + buffer_size_add_locked(prz, c); > > - start = buffer_start_add(prz, c); > + start = buffer_start_add_locked(prz, c); > > rem = prz->buffer_size - start; > if (unlikely(rem < c)) { > @@ -426,9 +390,6 @@ 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; > - > if (memtype) > va = ioremap(start, size); > else
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