From ee297209bf0a25c6717b7c063e76795142d32f37 Mon Sep 17 00:00:00 2001 From: Xiaotian Feng Date: Thu, 20 Dec 2012 15:05:44 -0800 Subject: [PATCH] proc: fix inconsistent lock state Lockdep found an inconsistent lock state when rcu is processing delayed work in softirq. Currently, kernel is using spin_lock/spin_unlock to protect proc_inum_ida, but proc_free_inum is called by rcu in softirq context. Use spin_lock_bh/spin_unlock_bh fix following lockdep warning. ================================= [ INFO: inconsistent lock state ] 3.7.0 #36 Not tainted --------------------------------- inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage. swapper/1/0 [HC0[0]:SC1[1]:HE1:SE0] takes: (proc_inum_lock){+.?...}, at: proc_free_inum+0x1c/0x50 {SOFTIRQ-ON-W} state was registered at: __lock_acquire+0x8ae/0xca0 lock_acquire+0x199/0x200 _raw_spin_lock+0x41/0x50 proc_alloc_inum+0x4c/0xd0 alloc_mnt_ns+0x49/0xc0 create_mnt_ns+0x25/0x70 mnt_init+0x161/0x1c7 vfs_caches_init+0x107/0x11a start_kernel+0x348/0x38c x86_64_start_reservations+0x131/0x136 x86_64_start_kernel+0x103/0x112 irq event stamp: 2993422 hardirqs last enabled at (2993422): _raw_spin_unlock_irqrestore+0x55/0x80 hardirqs last disabled at (2993421): _raw_spin_lock_irqsave+0x29/0x70 softirqs last enabled at (2993394): _local_bh_enable+0x13/0x20 softirqs last disabled at (2993395): call_softirq+0x1c/0x30 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(proc_inum_lock); lock(proc_inum_lock); *** DEADLOCK *** no locks held by swapper/1/0. stack backtrace: Pid: 0, comm: swapper/1 Not tainted 3.7.0 #36 Call Trace: [] ? vprintk_emit+0x471/0x510 print_usage_bug+0x2a5/0x2c0 mark_lock+0x33b/0x5e0 __lock_acquire+0x813/0xca0 lock_acquire+0x199/0x200 _raw_spin_lock+0x41/0x50 proc_free_inum+0x1c/0x50 free_pid_ns+0x1c/0x50 put_pid_ns+0x2e/0x50 put_pid+0x4a/0x60 delayed_put_pid+0x12/0x20 rcu_process_callbacks+0x462/0x790 __do_softirq+0x1b4/0x3b0 call_softirq+0x1c/0x30 do_softirq+0x59/0xd0 irq_exit+0x54/0xd0 smp_apic_timer_interrupt+0x95/0xa3 apic_timer_interrupt+0x72/0x80 cpuidle_enter_tk+0x10/0x20 cpuidle_enter_state+0x17/0x50 cpuidle_idle_call+0x287/0x520 cpu_idle+0xba/0x130 start_secondary+0x2b3/0x2bc Signed-off-by: Xiaotian Feng Cc: Al Viro Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/proc/generic.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/fs/proc/generic.c b/fs/proc/generic.c index 7b3ae3cc0ef9..e659a0ff1da7 100644 --- a/fs/proc/generic.c +++ b/fs/proc/generic.c @@ -359,18 +359,18 @@ retry: if (!ida_pre_get(&proc_inum_ida, GFP_KERNEL)) return -ENOMEM; - spin_lock(&proc_inum_lock); + spin_lock_bh(&proc_inum_lock); error = ida_get_new(&proc_inum_ida, &i); - spin_unlock(&proc_inum_lock); + spin_unlock_bh(&proc_inum_lock); if (error == -EAGAIN) goto retry; else if (error) return error; if (i > UINT_MAX - PROC_DYNAMIC_FIRST) { - spin_lock(&proc_inum_lock); + spin_lock_bh(&proc_inum_lock); ida_remove(&proc_inum_ida, i); - spin_unlock(&proc_inum_lock); + spin_unlock_bh(&proc_inum_lock); return -ENOSPC; } *inum = PROC_DYNAMIC_FIRST + i; @@ -379,9 +379,9 @@ retry: void proc_free_inum(unsigned int inum) { - spin_lock(&proc_inum_lock); + spin_lock_bh(&proc_inum_lock); ida_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST); - spin_unlock(&proc_inum_lock); + spin_unlock_bh(&proc_inum_lock); } static void *proc_follow_link(struct dentry *dentry, struct nameidata *nd) -- 2.34.1