modules: use raw_cpu_write for initialization of per cpu refcount.

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:

  __this_cpu_write operation in preemptible [00000000] code: modprobe/286
  caller is __this_cpu_preempt_check+0x38/0x60
  CPU: 3 PID: 286 Comm: modprobe Tainted: GF            3.12.0-rc4+ #187
  Call Trace:
    dump_stack+0x4e/0x82
    check_preemption_disabled+0xec/0x110
    __this_cpu_preempt_check+0x38/0x60
    load_module+0xcfd/0x2650
    SyS_init_module+0xa6/0xd0
    tracesys+0xe1/0xe6

Signed-off-by: Christoph Lameter <cl@linux.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/module.c b/kernel/module.c
index 29f7790eaa147a1b0fc7ec223c5356f44caab346..11869408f79b86abe33e5194d0f5c705b44e9d81 100644 (file)
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -640,7 +640,7 @@ static int module_unload_init(struct module *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);
 
        return 0;
 }