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SubjectRe: module: Optimize search_module_extables()
+++ Peter Zijlstra [08/02/17 15:48 +0100]:
>
>While looking through the __ex_table stuff I found that we do a linear
>lookup of the module. Also fix up a comment.
>
>Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Applied, thanks.

Hm. A quick scan through module.c still shows a couple of places that use
similar linear lookups, and may benefit from the same __module_address
optimization. But I'll save that for a separate patch..

Jessica

>---
> kernel/module.c | 27 ++++++++++++++-------------
> 1 file changed, 14 insertions(+), 13 deletions(-)
>
>diff --git a/kernel/module.c b/kernel/module.c
>index 3d8f126208e3..7bcdc35dbf95 100644
>--- a/kernel/module.c
>+++ b/kernel/module.c
>@@ -4165,22 +4165,23 @@ const struct exception_table_entry *search_module_extables(unsigned long addr)
> struct module *mod;
>
> preempt_disable();
>- list_for_each_entry_rcu(mod, &modules, list) {
>- if (mod->state == MODULE_STATE_UNFORMED)
>- continue;
>- if (mod->num_exentries == 0)
>- continue;
>+ mod = __module_address(addr);
>+ if (!mod)
>+ goto out;
>
>- e = search_extable(mod->extable,
>- mod->extable + mod->num_exentries - 1,
>- addr);
>- if (e)
>- break;
>- }
>+ if (!mod->num_exentries)
>+ goto out;
>+
>+ e = search_extable(mod->extable,
>+ mod->extable + mod->num_exentries - 1,
>+ addr);
>+out:
> preempt_enable();
>
>- /* Now, if we found one, we are running inside it now, hence
>- we cannot unload the module, hence no refcnt needed. */
>+ /*
>+ * Now, if we found one, we are running inside it now, hence
>+ * we cannot unload the module, hence no refcnt needed.
>+ */
> return e;
> }
>

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