linux-kernel - [PATCH] bpf: convert hashtab lock to raw lock

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Date:	Fri, 30 Oct 2015 15:16:26 -0700
From:	Yang Shi <yang.shi@...aro.org>
To:	ast@...nel.org, rostedt@...dmis.org
Cc:	linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
	netdev@...r.kernel.org, linaro-kernel@...ts.linaro.org,
	yang.shi@...aro.org
Subject: [PATCH] bpf: convert hashtab lock to raw lock

When running bpf samples on rt kernel, it reports the below warning:

BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917
in_atomic(): 1, irqs_disabled(): 128, pid: 477, name: ping
Preemption disabled at:[<ffff80000017db58>] kprobe_perf_func+0x30/0x228

CPU: 3 PID: 477 Comm: ping Not tainted 4.1.10-rt8 #4
Hardware name: Freescale Layerscape 2085a RDB Board (DT)
Call trace:
[<ffff80000008a5b0>] dump_backtrace+0x0/0x128
[<ffff80000008a6f8>] show_stack+0x20/0x30
[<ffff8000007da90c>] dump_stack+0x7c/0xa0
[<ffff8000000e4830>] ___might_sleep+0x188/0x1a0
[<ffff8000007e2200>] rt_spin_lock+0x28/0x40
[<ffff80000018bf9c>] htab_map_update_elem+0x124/0x320
[<ffff80000018c718>] bpf_map_update_elem+0x40/0x58
[<ffff800000187658>] __bpf_prog_run+0xd48/0x1640
[<ffff80000017ca6c>] trace_call_bpf+0x8c/0x100
[<ffff80000017db58>] kprobe_perf_func+0x30/0x228
[<ffff80000017dd84>] kprobe_dispatcher+0x34/0x58
[<ffff8000007e399c>] kprobe_handler+0x114/0x250
[<ffff8000007e3bf4>] kprobe_breakpoint_handler+0x1c/0x30
[<ffff800000085b80>] brk_handler+0x88/0x98
[<ffff8000000822f0>] do_debug_exception+0x50/0xb8
Exception stack(0xffff808349687460 to 0xffff808349687580)
7460: 4ca2b600 ffff8083 4a3a7000 ffff8083 49687620 ffff8083 0069c5f8 ffff8000
7480: 00000001 00000000 007e0628 ffff8000 496874b0 ffff8083 007e1de8 ffff8000
74a0: 496874d0 ffff8083 0008e04c ffff8000 00000001 00000000 4ca2b600 ffff8083
74c0: 00ba2e80 ffff8000 49687528 ffff8083 49687510 ffff8083 000e5c70 ffff8000
74e0: 00c22348 ffff8000 00000000 ffff8083 49687510 ffff8083 000e5c74 ffff8000
7500: 4ca2b600 ffff8083 49401800 ffff8083 00000001 00000000 00000000 00000000
7520: 496874d0 ffff8083 00000000 00000000 00000000 00000000 00000000 00000000
7540: 2f2e2d2c 33323130 00000000 00000000 4c944500 ffff8083 00000000 00000000
7560: 00000000 00000000 008751e0 ffff8000 00000001 00000000 124e2d1d 00107b77

Convert hashtab lock to raw lock to avoid such warning.

Signed-off-by: Yang Shi <yang.shi@...aro.org>
---
This patch is applicable to mainline kernel too.

 kernel/bpf/hashtab.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 83c209d..972b76b 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -17,7 +17,7 @@
 struct bpf_htab {
 	struct bpf_map map;
 	struct hlist_head *buckets;
-	spinlock_t lock;
+	raw_spinlock_t lock;
 	u32 count;	/* number of elements in this hashtable */
 	u32 n_buckets;	/* number of hash buckets */
 	u32 elem_size;	/* size of each element in bytes */
@@ -82,7 +82,7 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 	for (i = 0; i < htab->n_buckets; i++)
 		INIT_HLIST_HEAD(&htab->buckets[i]);
 
-	spin_lock_init(&htab->lock);
+	raw_spin_lock_init(&htab->lock);
 	htab->count = 0;
 
 	htab->elem_size = sizeof(struct htab_elem) +
@@ -230,7 +230,7 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 	l_new->hash = htab_map_hash(l_new->key, key_size);
 
 	/* bpf_map_update_elem() can be called in_irq() */
-	spin_lock_irqsave(&htab->lock, flags);
+	raw_spin_lock_irqsave(&htab->lock, flags);
 
 	head = select_bucket(htab, l_new->hash);
 
@@ -266,11 +266,11 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
 	} else {
 		htab->count++;
 	}
-	spin_unlock_irqrestore(&htab->lock, flags);
+	raw_spin_unlock_irqrestore(&htab->lock, flags);
 
 	return 0;
 err:
-	spin_unlock_irqrestore(&htab->lock, flags);
+	raw_spin_unlock_irqrestore(&htab->lock, flags);
 	kfree(l_new);
 	return ret;
 }
@@ -291,7 +291,7 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
 
 	hash = htab_map_hash(key, key_size);
 
-	spin_lock_irqsave(&htab->lock, flags);
+	raw_spin_lock_irqsave(&htab->lock, flags);
 
 	head = select_bucket(htab, hash);
 
@@ -304,7 +304,7 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
 		ret = 0;
 	}
 
-	spin_unlock_irqrestore(&htab->lock, flags);
+	raw_spin_unlock_irqrestore(&htab->lock, flags);
 	return ret;
 }
 
-- 
2.0.2

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