lkml.org 
[lkml]   [2013]   [Oct]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 4/6] Use raw_cpu_write for initialization of per cpu refcount.
On Tue, Oct 15, 2013 at 12:47:26PM -0500, Christoph Lameter wrote:
> The initialization of a structure is not subject to synchronization.
> The use of __this_cpu would trigger a false positive with the
> additional preemption checks for __this_cpu ops.
>
> So simply disable the check through the use of raw_cpu ops.
>
> Trace:
>
> [ 0.668066] __this_cpu_write operation in preemptible [00000000] code: modprobe/286
> [ 0.668108] caller is __this_cpu_preempt_check+0x38/0x60
> [ 0.668111] CPU: 3 PID: 286 Comm: modprobe Tainted: GF 3.12.0-rc4+ #187
> [ 0.668112] Hardware name: FUJITSU CELSIUS W530 Power/D3227-A1, BIOS V4.6.5.4 R1.10.0 for D3227-A1x 09/16/2013
> [ 0.668113] 0000000000000003 ffff8807edda1d18 ffffffff816d5a57 ffff8807edda1fd8
> [ 0.668117] ffff8807edda1d48 ffffffff8137359c ffff8807edda1ef8 ffffffffa0002178
> [ 0.668121] ffffc90000067730 ffff8807edda1e48 ffff8807edda1d88 ffffffff813735f8
> [ 0.668124] Call Trace:
> [ 0.668129] [<ffffffff816d5a57>] dump_stack+0x4e/0x82
> [ 0.668132] [<ffffffff8137359c>] check_preemption_disabled+0xec/0x110
> [ 0.668135] [<ffffffff813735f8>] __this_cpu_preempt_check+0x38/0x60
> [ 0.668139] [<ffffffff810c24fd>] load_module+0xcfd/0x2650
> [ 0.668143] [<ffffffff816dd922>] ? page_fault+0x22/0x30
> [ 0.668146] [<ffffffff810c3ef6>] SyS_init_module+0xa6/0xd0
> [ 0.668150] [<ffffffff816e4fd3>] tracesys+0xe1/0xe6
>
>
>
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> Signed-off-by: Christoph Lameter <cl@linux.com>
>
> Index: linux/kernel/module.c
> ===================================================================
> --- linux.orig/kernel/module.c 2013-09-05 13:43:30.557687773 -0500
> +++ linux/kernel/module.c 2013-10-07 12:33:43.732059759 -0500
> @@ -643,7 +643,7 @@ static int module_unload_init(struct mod
> INIT_LIST_HEAD(&mod->target_list);
>
> /* Hold reference count during initialization. */
> - __this_cpu_write(mod->refptr->incs, 1);
> + raw_cpu_write(mod->refptr->incs, 1);

Just add: Safe to use raw because we're the only user. So we all
instantly know.

> /* Backwards compatibility macros put refcount during init. */
> mod->waiter = current;
>
>


\
 
 \ /
  Last update: 2013-10-16 11:21    [W:0.136 / U:0.532 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site