Re: rcu-torture: Internal error: Oops: 96000006
From: "Paul E. McKenney" <paulmck@kernel.org>
Date: 2021-01-22 15:39:42
Also in:
linux-next, lkml, rcu
On Fri, Jan 22, 2021 at 03:21:07PM +0530, Naresh Kamboju wrote:
On Fri, 22 Jan 2021 at 03:13, Paul E. McKenney [off-list ref] wrote:quoted
On Thu, Jan 21, 2021 at 09:31:10PM +0000, Will Deacon wrote:quoted
On Thu, Jan 21, 2021 at 10:55:21AM -0800, Paul E. McKenney wrote:quoted
On Thu, Jan 21, 2021 at 10:37:21PM +0530, Naresh Kamboju wrote:quoted
While running rcu-torture test on qemu_arm64 and arm64 Juno-r2 device the following kernel crash noticed. This started happening from Linux next next-20210111 tag to next-20210121. metadata: git branch: master git repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next git describe: next-20210111 kernel-config: https://builds.tuxbuild.com/1muTTn7AfqcWvH5x2Alxifn7EUH/config output log: [ 621.538050] mem_dump_obj() slab test: rcu_torture_stats = ffff0000c0a3ac40, &rhp = ffff800012debe40, rhp = ffff0000c8cba000, &z = ffff8000091ab8e0 [ 621.546662] mem_dump_obj(ZERO_SIZE_PTR): [ 621.546696] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008[...]quoted
Huh. I am relying on virt_addr_valid() rejecting NULL pointers and things like ZERO_SIZE_PTR, which is defined as ((void *)16). It looks like your configuration rejects NULL as an invalid virtual address, but does not reject ZERO_SIZE_PTR. Is this the intent, given that you are not allowed to dereference a ZERO_SIZE_PTR? Adding the ARM64 guys on CC for their thoughts.Spooky timing, there was a thread _today_ about that: https://lore.kernel.org/r/ecbc7651-82c4-6518-d4a9-dbdbdf833b5b@arm.com (local)Very good, then my workaround (shown below for Naresh's ease of testing) is only a short-term workaround. Yay! ;-)Paul, thanks for your (short-term workaround) patch. I have applied your patch and tested rcu-torture test on qemu_arm64 and the reported issues has been fixed.
May I add your Tested-by? And before I forget again, good to see the rcutorture testing on a non-x86 platform! Thanx, Paul _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel