Commit 08f141d3 authored Apr 07, 2014 by Christoph Lameter Committed by Linus Torvalds Apr 07, 2014

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>

parent dc322a99

kernel/module.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}

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