From: Zhang, Yanmin Date: Wed, 14 Aug 2030 07:56:40 +0000 (+0800) Subject: sched: fix the race between walk_tg_tree and sched_create_group X-Git-Tag: v2.6.27-rc4~51^2~2 X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=09f2724a786f76475ef2985cf84f5359c553aade;p=linux-2.6-omap-h63xx.git sched: fix the race between walk_tg_tree and sched_create_group With 2.6.27-rc3, I hit a kernel panic when running volanoMark on my new x86_64 machine. I also hit it with other 2.6.27-rc kernels. See below log. Basically, function walk_tg_tree and sched_create_group have a race between accessing and initiating tg->children. Below patch fixes it by moving tg->children initiation to the front of linking tg->siblings to parent->children. {----------------panic log------------} BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 IP: [] walk_tg_tree+0x45/0x7f PGD 1be1c4067 PUD 1bdd8d067 PMD 0 Oops: 0000 [1] SMP CPU 11 Modules linked in: igb Pid: 22979, comm: java Not tainted 2.6.27-rc3 #1 RIP: 0010:[] [] walk_tg_tree+0x45/0x7f RSP: 0018:ffff8801bfbbbd18 EFLAGS: 00010083 RAX: 0000000000000000 RBX: ffff8800be0dce40 RCX: ffffffffffffffc0 RDX: ffff880102c43740 RSI: 0000000000000000 RDI: ffff8800be0dce40 RBP: ffff8801bfbbbd48 R08: ffff8800ba437bc8 R09: 0000000000001f40 R10: ffff8801be812100 R11: ffffffff805fdf44 R12: ffff880102c43740 R13: 0000000000000000 R14: ffffffff8022cf0f R15: ffffffff8022749f FS: 00000000568ac950(0063) GS:ffff8801bfa26d00(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 0000000000000000 CR3: 00000001bd848000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process java (pid: 22979, threadinfo ffff8801b145a000, task ffff8801bf18e450) Stack: 0000000000000001 ffff8800ba5c8d60 0000000000000001 0000000000000001 ffff8800bad1ccb8 0000000000000000 ffff8801bfbbbd98 ffffffff8022ed37 0000000000000001 0000000000000286 ffff8801bd5ee180 ffff8800ba437bc8 Call Trace: [] try_to_wake_up+0x71/0x24c [] autoremove_wake_function+0x9/0x2e [] ? __wake_up_common+0x46/0x76 [] __wake_up+0x38/0x4f [] tcp_v4_rcv+0x380/0x62e Signed-off-by: Zhang Yanmin Acked-by: Peter Zijlstra Signed-off-by: Ingo Molnar --- diff --git a/kernel/sched.c b/kernel/sched.c index d601fb0406c..8bf8a5528bc 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -8462,8 +8462,8 @@ struct task_group *sched_create_group(struct task_group *parent) WARN_ON(!parent); /* root should already exist */ tg->parent = parent; - list_add_rcu(&tg->siblings, &parent->children); INIT_LIST_HEAD(&tg->children); + list_add_rcu(&tg->siblings, &parent->children); spin_unlock_irqrestore(&task_group_lock, flags); return tg;