From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Date: Sun, 22 Mar 2015 23:35:49 +0000 Subject: Re: 4.0.0-rc4: panic in free_block Message-Id: <550F51D5.2010804@oracle.com> List-Id: References: <20150322.133603.471287558426791155.davem@davemloft.net> <20150322.182311.109269221031797359.davem@davemloft.net> In-Reply-To: <20150322.182311.109269221031797359.davem@davemloft.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: David Miller , torvalds@linux-foundation.org Cc: sparclinux@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Bob Picco On 3/22/15 4:23 PM, David Miller wrote: >> I don't even know which version of memcpy ends up being used on M7. >> Some of them do things like use VIS. I can follow some regular sparc >> asm, there's no way I'm even *looking* at that. Is it really ok to use >> VIS registers in random contexts? > > Yes, using VIS how we do is alright, and in fact I did an audit of > this about 1 year ago. This is another one of those "if this is > wrong, so much stuff would break" > > The only thing funny some of these routines do is fetch 2 64-byte > blocks of data ahead in the inner loops, but that should be fine > right? > > On the M7 we'll use the Niagara-4 memcpy. > > Hmmm... I'll run this silly sparc kernel memmove through the glibc > testsuite and see if it barfs. > I don't know if you caught Bob's message; he has a hack to bypass memcpy and memmove in mm/slab.c use a for loop to move entries. With the hack he is not seeing the problem. This is the hack: +static void move_entries(void *dest, void *src, int nr) +{ + unsigned long *dp = dest; + unsigned long *sp = src; + + for (; nr; nr--, dp++, sp++) + *dp = *sp; +} + and then replace the mempy and memmove calls in transfer_objects, cache_flusharray and drain_array to use move_entries. I just put it on 4.0.0-rc4 and ditto -- problem goes away, so it clearly suggests the memcpy or memmove are the root cause. David