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Date: Sat, 25 Feb 2017 22:39:50 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Fengguang Wu <fengguang.wu@...el.com>
Cc: LKP <lkp@...org>, netdev@...r.kernel.org,
Thomas Graf <tgraf@...g.ch>
Subject: Re: [rhashtable] 5d60de5ff1 [ INFO: suspicious RCU usage. ]
On Sat, Feb 18, 2017 at 01:23:31PM +0800, Fengguang Wu wrote:
> Greetings,
>
> 0day kernel testing robot got the below dmesg and the first bad commit is
>
> https://github.com/0day-ci/linux Herbert-Xu/rhashtable-Handle-table-allocation-failure-during-insertion/20170212-030221
>
> commit 5d60de5ff12fb1e966c863bcb41c1e2bdde66c50
> Author: Herbert Xu <herbert@...dor.apana.org.au>
> AuthorDate: Sat Feb 11 19:26:47 2017 +0800
> Commit: 0day robot <fengguang.wu@...el.com>
> CommitDate: Sun Feb 12 03:02:26 2017 +0800
>
> rhashtable: Add nested tables
>
> This patch adds code that handles GFP_ATOMIC kmalloc failure on
> insertion. As we cannot use vmalloc, we solve it by making our
> hash table nested. That is, we allocate single pages at each level
> and reach our desired table size by nesting them.
>
> When a nested table is created, only a single page is allocated
> at the top-level. Lower levels are allocated on demand during
> insertion. Therefore for each insertion to succeed, only two
> (non-consecutive) pages are needed.
>
> After a nested table is created, a rehash will be scheduled in
> order to switch to a vmalloced table as soon as possible. Also,
> the rehash code will never rehash into a nested table. If we
> detect a nested table during a rehash, the rehash will be aborted
> and a new rehash will be scheduled.
>
> Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
>
> +------------------------------------------------------------------+------------+------------+------------------+
> | | eadcee1e3a | 5d60de5ff1 | v4.10-rc8_021716 |
> +------------------------------------------------------------------+------------+------------+------------------+
> | boot_successes | 0 | 0 | 9 |
> | boot_failures | 177 | 48 | 82 |
> | Kernel_panic-not_syncing:softlockup:hung_tasks | 177 | 48 | 14 |
> | INFO:suspicious_RCU_usage | 0 | 39 | 64 |
> | BUG:KASAN:user-memory-access_on_address | 0 | 0 | 16 |
> | BUG:unable_to_handle_kernel | 0 | 0 | 18 |
> | Oops | 0 | 0 | 18 |
> | Kernel_panic-not_syncing:Fatal_exception | 0 | 0 | 18 |
> | BUG:kernel_hang_in_test_stage | 0 | 0 | 19 |
> | WARNING:at_kernel/sched/sched.h:#set_next_entity | 0 | 0 | 15 |
> | INFO:possible_circular_locking_dependency_detected | 0 | 0 | 4 |
> | WARNING:at_include/linux/cpumask.h:#find_get_context | 0 | 0 | 2 |
> | invoked_oom-killer:gfp_mask=0x | 0 | 0 | 4 |
> | Mem-Info | 0 | 0 | 4 |
> | Kernel_panic-not_syncing:Out_of_memory_and_no_killable_processes | 0 | 0 | 4 |
> | Kernel_panic-not_syncing:Attempted_to_kill_init!exitcode= | 0 | 0 | 7 |
> +------------------------------------------------------------------+------------+------------+------------------+
>
> [ 9.022401] Testing concurrent rhashtable access from 10 threads
> [ 15.800003]
> [ 15.801145] ===============================
> [ 15.801802] [ INFO: suspicious RCU usage. ]
> [ 15.802476] 4.10.0-rc7-00090-g5d60de5 #1 Not tainted
> [ 15.803235] -------------------------------
> [ 15.803866] lib/rhashtable.c:1126 suspicious rcu_dereference_protected() usage!
Sorry, I chose the wrong annotation to fix the previous report.
This patch should fix it completely.
---8<---
Subject: rhashtable: Fix RCU dereference annotation in rht_bucket_nested
The current annotation is wrong as it says that we're only called
under spinlock. In fact it should be marked as under either
spinlock or RCU read lock.
Fixes: da20420f83ea ("rhashtable: Add nested tables")
Reported-by: Fengguang Wu <fengguang.wu@...el.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
---
lib/rhashtable.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index fac1a78..c5b9b93 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -1121,12 +1121,13 @@ struct rhash_head __rcu **rht_bucket_nested(const struct bucket_table *tbl,
union nested_table *ntbl;
ntbl = (union nested_table *)rcu_dereference_raw(tbl->buckets[0]);
- ntbl = rht_dereference_bucket(ntbl[index].table, tbl, hash);
+ ntbl = rht_dereference_bucket_rcu(ntbl[index].table, tbl, hash);
subhash >>= tbl->nest;
while (ntbl && size > (1 << shift)) {
index = subhash & ((1 << shift) - 1);
- ntbl = rht_dereference_bucket(ntbl[index].table, tbl, hash);
+ ntbl = rht_dereference_bucket_rcu(ntbl[index].table,
+ tbl, hash);
size >>= shift;
subhash >>= shift;
}
--
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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