From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934248AbcIHVcL (ORCPT ); Thu, 8 Sep 2016 17:32:11 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:60830 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932294AbcIHVcJ (ORCPT ); Thu, 8 Sep 2016 17:32:09 -0400 Date: Thu, 8 Sep 2016 14:32:05 -0700 From: Guenter Roeck To: Sebastian Andrzej Siewior Cc: linux-kernel@vger.kernel.org, Anton Vorontsov , Colin Cross , Kees Cook , Tony Luck Subject: Re: pstore/core: drop cmpxchg based updates Message-ID: <20160908213205.GA4276@roeck-us.net> References: <20160824130935.23110-1-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20160824130935.23110-1-bigeasy@linutronix.de> User-Agent: Mutt/1.5.23 (2014-03-12) X-Authenticated_sender: guenter@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: guenter@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: guenter@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > Cc: Colin Cross > Cc: Kees Cook > Cc: Tony Luck > Signed-off-by: Sebastian Andrzej Siewior > Tested-by: Rabin Vincent 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 > --- > 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