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    SubjectRe: [PATCH] fix error handling in load_module()
    * Rusty Russell <rusty@rustcorp.com.au> [2009-09-22 14:35:21]:

    > On Tue, 22 Sep 2009 12:11:21 am Tejun Heo wrote:
    > > Hello, Andrew.
    > >
    > > Andrew Morton wrote:
    > > > My reverse engineering of the secret, undocumented percpu_modfree()
    > > > indicates that its mad inventor intended that percpu_modfree(NULL) be a
    > > > valid thing to do.
    > > >
    > > > It calls free_percpu(), all implementations of which appear to secretly
    > > > support free_percpu(NULL).
    > >
    > > Eh... unfortunately, the original percpu_modfree() implementation
    > > didn't seem to support it.
    >
    > OK, I'll Andrew's fix for Tejun, and after his (spot-on!) comment about
    > percpu_modfree never taking NULL, I've fixed the one caller to match
    > the other two:
    >
    > Subject: module: don't call percpu_modfree on NULL pointer.
    >
    > The general one handles NULL, the static obsolescent
    > (CONFIG_HAVE_LEGACY_PER_CPU_AREA) one in module.c doesn't; Eric's
    > commit 720eba31 assumed it did, and various frobbings since then kept
    > that assumption.
    >
    > All other callers in module.c all protect it with an if; this effectively
    > does the same as free_init is only goto if we fail percpu_modalloc().

    Thanks, the patch fixes the issue.

    > Reported-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
    > Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
    > Cc: Eric Dumazet <dada1@cosmosbay.com>
    > Cc: Masami Hiramatsu <mhiramat@redhat.com>
    > Cc: Américo Wang <xiyou.wangcong@gmail.com>
    >
    > diff --git a/kernel/module.c b/kernel/module.c
    > --- a/kernel/module.c
    > +++ b/kernel/module.c
    > @@ -2522,8 +2522,8 @@ static noinline struct module *load_modu
    > free_unload:
    > module_unload_free(mod);
    > #if defined(CONFIG_MODULE_UNLOAD) && defined(CONFIG_SMP)
    > + percpu_modfree(mod->refptr);
    > free_init:
    > - percpu_modfree(mod->refptr);
    > #endif
    > module_free(mod, mod->module_init);
    > free_core:
    > --
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    Kamalesh
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