linux-kernel - [PATCH linux-next] ipc: Avoid sleeping inside RCU.

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Date:	Mon, 17 Jun 2013 20:55:04 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	davidlohr.bueso@...com, akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH linux-next] ipc: Avoid sleeping inside RCU.

I got this.

===============================
[ INFO: suspicious RCU usage. ]
3.10.0-rc6-next-20130617 #7 Not tainted
-------------------------------
include/linux/rcupdate.h:475 Illegal context switch in RCU read-side critical section!

other info that might help us debug this:


rcu_scheduler_active = 1, debug_locks = 1
2 locks held by udevd/1909:
 #0:  (&ids->rw_mutex){+.+.+.}, at: [<c038c4b5>] ipcget+0x45/0x70
 #1:  (rcu_read_lock){.+.+..}, at: [<c038df60>] rcu_read_lock+0x0/0x80

stack backtrace:
CPU: 0 PID: 1909 Comm: udevd Not tainted 3.10.0-rc6-next-20130617 #7
Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 08/15/2008
 00000001 da591e94 c0677931 00000001 da591ebc c0199606 c07f690d c07f83fa
 00000001 00000001 c07e7904 00000000 000001a8 c081e5f7 da591ee4 c0176231
 00000246 00000002 00000001 00000000 00000000 000000d0 deee0f0c ffffffe4
Call Trace:
 [<c0677931>] dump_stack+0x4c/0x6b
 [<c0199606>] lockdep_rcu_suspicious+0xc6/0x100
 [<c0176231>] __might_sleep+0xb1/0x200
 [<c04098f1>] idr_preload+0xa1/0xd0
 [<c038b4d2>] ipc_addid+0x52/0x190
 [<c038dfbd>] ? rcu_read_lock+0x5d/0x80
 [<c038e7aa>] newary+0xba/0x1a0
 [<c038c4be>] ipcget+0x4e/0x70
 [<c019d7a2>] ? __lock_release+0x72/0x1b0
 [<c038e6cf>] SyS_semget+0x6f/0x80
 [<c038e6f0>] ? sem_security+0x10/0x10
 [<c038e6e0>] ? SyS_semget+0x80/0x80
 [<c038dd80>] ? SyS_msgctl+0xb0/0xb0
 [<c0392ab3>] SyS_ipc+0xa3/0x250
 [<c0235426>] ? vm_munmap+0x46/0x60
 [<c067c89a>] sysenter_do_call+0x12/0x32
BUG: sleeping function called from invalid context at lib/idr.c:424
in_atomic(): 1, irqs_disabled(): 0, pid: 1909, name: udevd
2 locks held by udevd/1909:
 #0:  (&ids->rw_mutex){+.+.+.}, at: [<c038c4b5>] ipcget+0x45/0x70
 #1:  (rcu_read_lock){.+.+..}, at: [<c038df60>] rcu_read_lock+0x0/0x80
CPU: 0 PID: 1909 Comm: udevd Not tainted 3.10.0-rc6-next-20130617 #7
Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 08/15/2008
 000001a8 da591ebc c0677931 da594260 da591ee4 c01762dd c07e79fc 00000001
 00000000 00000775 da594518 000000d0 deee0f0c ffffffe4 da591ef0 c04098f1
 c08e2b84 da591f10 c038b4d2 da591f10 c038dfbd ffffffff 00000001 c08e2b80
Call Trace:
 [<c0677931>] dump_stack+0x4c/0x6b
 [<c01762dd>] __might_sleep+0x15d/0x200
 [<c04098f1>] idr_preload+0xa1/0xd0
 [<c038b4d2>] ipc_addid+0x52/0x190
 [<c038dfbd>] ? rcu_read_lock+0x5d/0x80
 [<c038e7aa>] newary+0xba/0x1a0
 [<c038c4be>] ipcget+0x4e/0x70
 [<c019d7a2>] ? __lock_release+0x72/0x1b0
 [<c038e6cf>] SyS_semget+0x6f/0x80
 [<c038e6f0>] ? sem_security+0x10/0x10
 [<c038e6e0>] ? SyS_semget+0x80/0x80
 [<c038dd80>] ? SyS_msgctl+0xb0/0xb0
 [<c0392ab3>] SyS_ipc+0xa3/0x250
 [<c0235426>] ? vm_munmap+0x46/0x60
 [<c067c89a>] sysenter_do_call+0x12/0x32

----------
>>From da6fbd77764e01cd611bd488666f349c11e1d4f3 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Date: Mon, 17 Jun 2013 20:49:25 +0900
Subject: [PATCH linux-next] ipc: Avoid sleeping inside RCU.

Commit 4964214b "ipc: move rcu lock out of ipc_addid" moved
idr_preload(GFP_KERNEL) into RCU read-side critical section.

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
---
 ipc/util.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/ipc/util.c b/ipc/util.c
index a746abb..00aca85 100644
--- a/ipc/util.c
+++ b/ipc/util.c
@@ -261,7 +261,7 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size)
 	if (ids->in_use >= size)
 		return -ENOSPC;
 
-	idr_preload(GFP_KERNEL);
+	idr_preload(GFP_ATOMIC);
 
 	spin_lock_init(&new->lock);
 	new->deleted = 0;
-- 
1.7.1
--
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