Messages in this thread | | | Date | Tue, 7 Nov 2017 20:29:11 +0800 | From | Fengguang Wu <> | Subject | Re: [gcov_enable_events] WARNING: bad unlock balance detected! |
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Sorry please ignore this report -- according to Peter:
This is fixed by commit:
02a7c234e540 ("rcu: Suppress lockdep false-positive ->boost_mtx complaints")
The problem is that RCU boosting was mixing futex and !futex rt_mutex ops. On Tue, Nov 07, 2017 at 09:52:09AM +0800, Fengguang Wu wrote: >Hi, > >Here is a warning in v4.14-rc8 -- it's not necessarily a new bug. > >[ 29.314270] rcu-perf: rcu_perf_writer task started >[ 29.329146] audit: initializing netlink subsys (disabled) >[ 29.337989] audit: type=2000 audit(1510004207.289:1): state=initialized audit_enabled=0 res=1 >[ 39.708008] >[ 39.710234] ===================================== >[ 39.710234] WARNING: bad unlock balance detected! >[ 39.710234] 4.14.0-rc8 #1 Not tainted >[ 39.710234] ------------------------------------- >[ 39.710234] swapper/0/1 is trying to release lock (rcu_preempt_state) at: >[ 39.710234] [<cb4992e3>] rcu_read_unlock_special+0x6e3/0x800 >[ 39.710234] but there are no more locks to release! >[ 39.710234] >[ 39.710234] other info that might help us debug this: >[ 39.710234] 4 locks held by swapper/0/1: >[ 39.710234] #0: (gcov_lock){+.+.}, at: [<cb5176b3>] gcov_enable_events+0x23/0xc0 >[ 39.710234] #1: (node_lock){+.+.}, at: [<cb518cef>] gcov_event+0x2f/0x7a0 >[ 39.710234] #2: (&sb->s_type->i_mutex_key#3){+.+.}, at: [<cb7d645d>] start_creating+0xcd/0x240 >[ 39.710234] #3: (rcu_read_lock){....}, at: [<cb6e3b20>] __d_lookup+0x0/0x520 >[ 39.710234] >[ 39.710234] stack backtrace: >[ 39.710234] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.14.0-rc8 #1 >[ 39.710234] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014 >[ 39.710234] Call Trace: >[ 39.710234] dump_stack+0x146/0x1e6 >[ 39.710234] ? rcu_read_unlock_special+0x6e3/0x800 >[ 39.710234] print_unlock_imbalance_bug+0x1cc/0x1f0 >[ 39.710234] ? rcu_read_unlock_special+0x6e3/0x800 >[ 39.710234] lock_release+0x41b/0xa90 >[ 39.710234] ? mark_held_locks+0xd7/0x120 >[ 39.710234] ? rcu_read_unlock_special+0x6e3/0x800 >[ 39.710234] rt_mutex_unlock+0x3f/0x170 >[ 39.710234] ? _raw_spin_unlock_irqrestore+0x133/0x170 >[ 39.710234] rcu_read_unlock_special+0x6e3/0x800 >[ 39.710234] ? __lock_is_held+0x58/0xe0 >[ 39.710234] __rcu_read_unlock+0xbc/0x180 >[ 39.710234] __d_lookup+0x4de/0x520 >[ 39.710234] ? __d_lookup_rcu+0x420/0x420 >[ 39.710234] ? d_lookup+0x11b/0x240 >[ 39.710234] ? trace_hardirqs_on_caller+0x2d2/0x430 >[ 39.710234] d_lookup+0x1b7/0x240 >[ 39.710234] ? lookup_dcache+0x2f/0x170 >[ 39.710234] lookup_dcache+0x2f/0x170 >[ 39.710234] __lookup_hash+0x2e/0x1c0 >[ 39.710234] lookup_one_len+0x282/0x2a0 >[ 39.710234] start_creating+0xfb/0x240 >[ 39.710234] __debugfs_create_file+0xc7/0x2f0 >[ 39.710234] debugfs_create_file+0x50/0x70 >[ 39.710234] new_node+0x1b5/0x350 >[ 39.710234] gcov_event+0x344/0x7a0 >[ 39.710234] ? gcov_persist_setup+0x90/0x90 >[ 39.710234] gcov_enable_events+0x57/0xc0 >[ 39.710234] gcov_fs_init+0xf3/0x13d >[ 39.710234] do_one_initcall+0x113/0x2b1 >[ 39.710234] ? kernel_init_freeable+0x236/0x3b4 >[ 39.710234] kernel_init_freeable+0x260/0x3b4 >[ 39.710234] ? rest_init+0x440/0x440 >[ 39.710234] kernel_init+0x1e/0x290 >[ 39.710234] ? schedule_tail_wrapper+0x9/0xc >[ 39.710234] ret_from_fork+0x19/0x24 >[ 40.559851] rcu-perf: rcu_perf_writer 1 has 100 measurements >[ 40.567049] rcu-perf: rcu_perf_writer 0 has 100 measurements >[ 40.617286] Dumping ftrace buffer: >[ 40.620255] (ftrace buffer empty) >[ 40.628854] rcu-perf: Test complete > >Thanks, >Fengguang
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