Messages in this thread | | | Date | Tue, 10 Dec 2013 14:29:20 +0800 | Subject | Re: ARM: nommu: DEBUG_LOCKS_WARN_ON(!depth) | From | Axel Lin <> |
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2013/11/25 Axel Lin <axel.lin@ingics.com>: > I'm testing on a nommu platform (arm7tdmi SoC). > Using current Linus' tree + out-of-tree patches for this SoC. > I got below hang while executing ls (busybox) after boot. > > / # ls > [ 51.036191] ------------[ cut here ]------------ > [ 51.042242] WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:3312 lock_set_class+0x5c8/0x660() > [ 51.051426] DEBUG_LOCKS_WARN_ON(!depth) > [ 51.055842] CPU: 0 PID: 1 Comm: Not tainted 3.13.0-rc1-00100-g4b061f7-dirty #1917 > [ 51.065415] [<0000c430>] (unwind_backtrace+0x0/0xe0) from [<0000ae58>] (show_stack+0x10/0x14) > [ 51.075781] [<0000ae58>] (show_stack+0x10/0x14) from [<0000f7b0>] (warn_slowpath_common+0x58/0x78) > [ 51.086549] [<0000f7b0>] (warn_slowpath_common+0x58/0x78) from [<0000f814>] (warn_slowpath_fmt+0x2c/0x3c) > [ 51.098162] [<0000f814>] (warn_slowpath_fmt+0x2c/0x3c) from [<00036d9c>] (lock_set_class+0x5c8/0x660) > [ 50.934805] [<00036d9c>] (lock_set_class+0x5c8/0x660) from [<000367d4>] (lock_set_class+0x0/0x660) > [ 50.945255] [<000367d4>] (lock_set_class+0x0/0x660) from [<00000000>] ( (null)) > [ 50.953242] ---[ end trace 7d1e4eb800000001 ]--- >
Now test on top of linux-3.13-rc3. I found I can hit this lockdep warning only when CONFIG_PREEMPT_NONE=y
1) With CONFIG_PREEMPT_NONE=y executing ls (busybox) hang with above lockdep warning. 2) With CONFIG_PREEMPT_VOLUNTARY=y: have "[sched_delayed] sched: RT throttling activated" in boot message. executing ls (busybox) hang silently. 3) With CONFIG_PREEMPT=y: executing ls (busybox) successfully and it's ok to execute other binary.
all the test with below configs: CONFIG_PREEMPT_COUNT=y CONFIG_DEBUG_SPINLOCK=y CONFIG_DEBUG_MUTEXES=y CONFIG_DEBUG_WW_MUTEX_SLOWPATH=y CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_PROVE_LOCKING=y CONFIG_LOCKDEP=y CONFIG_DEBUG_ATOMIC_SLEEP=y CONFIG_TRACE_IRQFLAGS=y CONFIG_STACKTRACE=y CONFIG_DEBUG_BUGVERBOSE=y
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