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Subject[RESEND PATCH] slab: skip kmemleak_object in leaks_show()
Date
Running tests on a debug kernel will usually generate a large number of
kmemleak objects.

# grep kmemleak /proc/slabinfo
kmemleak_object 2243606 3436210 ...

As the result, reading /proc/slab_allocators could easily loop forever
while processing the kmemleak_object cache and any additional freeing or
allocating objects will trigger a reprocessing. To make a situation
worse, soft-lockups could easily happen in this sitatuion which will
call printk() to allocate more kmemleak objects to guarantee a livelock.

Since kmemleak_object has a single call site (create_object()), there
isn't much new information compared with slabinfo. Just skip it.

Signed-off-by: Qian Cai <cai@lca.pw>
---
mm/slab.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/mm/slab.c b/mm/slab.c
index 20f318f4f56e..85d1d223f879 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4285,6 +4285,15 @@ static int leaks_show(struct seq_file *m, void *p)
if (!(cachep->flags & SLAB_RED_ZONE))
return 0;

+ /*
+ * /proc/slabinfo has the same information, so skip kmemleak here due to
+ * a high volume and its RCU free could make cachep->store_user_clean
+ * dirty all the time.
+ */
+ if (IS_ENABLED(CONFIG_DEBUG_KMEMLEAK) &&
+ !strcmp("kmemleak_object", cachep->name))
+ return 0;
+
/*
* Set store_user_clean and start to grab stored user information
* for all objects on this cache. If some alloc/free requests comes
--
2.20.1 (Apple Git-117)
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