Messages in this thread | | | From | "Zhengyejian (Zetta)" <> | Subject | [BUG] I found a bug when try to enable record_ftrace | Date | Wed, 2 Jun 2021 15:42:23 +0800 |
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Hello,
There may be a deadlock caused by ftrace recursion when try to enable record_ftrace. I'd like to known if the patchset (https://lore.kernel.org/lkml/20201106023235.367190737@goodmis.org/) is trying to fix it.
Procedure for reproducing the problem is: 1) this problem appears both in 5.13-rc4 and 5.10;
2) my work environment is: qemu-arm version 4.0.0 arm-linux-gnueabi-gcc (Ubuntu/Linaro 7.5.0-3ubuntu1~18.04) 7.5.0
3) then try to enable record_ftrace: / # mount -t pstore pstore /sys/fs/pstore / # echo 1 > /sys/kernel/debug/pstore/record_ftrace
4) then system appears to be stuck, and use arm-linux-gnueabi-gdb dump the following call stack: #0 arch_spin_lock (lock=0x811a0f98) at /home/zyj/Linux/linux-master/arch/arm/include/asm/spinlock.h:74 #1 do_raw_spin_lock_flags (flags=<synthetic pointer>, lock=0x811a0f98) at /home/zyj/Linux/linux-master/include/linux/spinlock.h:195 #2 __raw_spin_lock_irqsave (lock=0x811a0f98) at /home/zyj/Linux/linux-master/include/linux/spinlock_api_smp.h:119 #3 _raw_spin_lock_irqsave (lock=lock@entry=0x811a0f98) at /home/zyj/Linux/linux-master/kernel/locking/spinlock.c:159 #4 0x8046c6e0 in buffer_size_add (prz=prz@entry=0x811a0f80, a=a@entry=16) at /home/zyj/Linux/linux-master/fs/pstore/ram_core.c:82 #5 0x8046cc20 in persistent_ram_write (prz=0x811a0f80, s=0x81137b80, count=16) at /home/zyj/Linux/linux-master/fs/pstore/ram_core.c:327 #6 0x8046b438 in ramoops_pstore_write (record=0x81137b90) at /home/zyj/Linux/linux-master/fs/pstore/ram.c:331 #7 0x8046add8 in pstore_ftrace_call (ip=2156609456, parent_ip=2152122068, op=<optimized out>, fregs=<optimized out>) at /home/zyj/Linux/linux-master/fs/pstore/ftrace.c:54 #8 0x801dd580 in __ftrace_ops_list_func (ignored=0x0, fregs=0x0, parent_ip=2152122068, ip=2156609456) at /home/zyj/Linux/linux-master/kernel/trace/ftrace.c:7003 #9 ftrace_ops_list_func (ip=2156609456, parent_ip=2152122068, op=<optimized out>, fregs=0x0) at /home/zyj/Linux/linux-master/kernel/trace/ftrace.c:7028 #10 0x801109f8 in ftrace_caller () at /home/zyj/Linux/linux-master/arch/arm/kernel/entry-ftrace.S:224 #11 0x808b3fb4 in _raw_spin_unlock_irqrestore (lock=lock@entry=0x811a0f98, flags=1610612883) at /home/zyj/Linux/linux-master/kernel/locking/spinlock.c:190 #12 0x8046c6d4 in buffer_size_add (prz=prz@entry=0x811a0f80, a=a@entry=16) at /home/zyj/Linux/linux-master/fs/pstore/ram_core.c:95 #13 0x8046cc20 in persistent_ram_write (prz=0x811a0f80, s=0x81137cf8, count=16) at /home/zyj/Linux/linux-master/fs/pstore/ram_core.c:327 #14 0x8046b438 in ramoops_pstore_write (record=0x81137d08) at /home/zyj/Linux/linux-master/fs/pstore/ram.c:331 #15 0x8046add8 in pstore_ftrace_call (ip=2148632188, parent_ip=2148601660, op=<optimized out>, fregs=<optimized out>) at /home/zyj/Linux/linux-master/fs/pstore/ftrace.c:54 #16 0x801dd580 in __ftrace_ops_list_func (ignored=0x0, fregs=0x0, parent_ip=2148601660, ip=2148632188) at /home/zyj/Linux/linux-master/kernel/trace/ftrace.c:7003 #17 ftrace_ops_list_func (ip=2148632188, parent_ip=2148601660, op=<optimized out>, fregs=0x0) at /home/zyj/Linux/linux-master/kernel/trace/ftrace.c:7028 #18 0x801109f8 in ftrace_caller () at /home/zyj/Linux/linux-master/arch/arm/kernel/entry-ftrace.S:224 #19 0x80118680 in __set_fixmap (idx=idx@entry=FIX_TEXT_POKE0, phys=phys@entry=0, prot=prot@entry=0) at /home/zyj/Linux/linux-master/arch/arm/mm/mmu.c:385 #20 0x80110f3c in patch_unmap (flags=<synthetic pointer>, fixmap=129) at /home/zyj/Linux/linux-master/arch/arm/kernel/patch.c:45 #21 __patch_text_real (addr=addr@entry=0x808b3fb0 <_raw_spin_unlock_irqrestore+16>, insn=insn@entry=3957420680, remap=remap@entry=true) at /home/zyj/Linux/linux-master/arch/arm/kernel/patch.c:104 #22 0x80110b40 in __patch_text (insn=3957420680, addr=0x808b3fb0 <_raw_spin_unlock_irqrestore+16>) at /home/zyj/Linux/linux-master/arch/arm/include/asm/patch.h:10 #23 ftrace_modify_code (pc=2156609456, old=3904716800, new=3957420680, validate=true) at /home/zyj/Linux/linux-master/arch/arm/kernel/ftrace.c:95 #24 0x80110cf4 in ftrace_make_call (rec=rec@entry=0x81007ce0, addr=addr@entry=2148600280) at /home/zyj/Linux/linux-master/arch/arm/kernel/ftrace.c:132 #25 0x801dda40 in __ftrace_replace_code (rec=rec@entry=0x81007ce0, enable=enable@entry=true) at /home/zyj/Linux/linux-master/kernel/trace/ftrace.c:2524 #26 0x801de17c in ftrace_replace_code (mod_flags=mod_flags@entry=1) at /home/zyj/Linux/linux-master/kernel/trace/ftrace.c:2554 #27 0x801de39c in ftrace_modify_all_code (command=5) at /home/zyj/Linux/linux-master/kernel/trace/ftrace.c:2698 #28 0x80110ad8 in __ftrace_modify_code (data=<optimized out>) at /home/zyj/Linux/linux-master/arch/arm/kernel/ftrace.c:39 #29 0x801d4da4 in multi_cpu_stop (data=data@entry=0x81c69d84) at /home/zyj/Linux/linux-master/kernel/stop_machine.c:240 #30 0x801d4a14 in cpu_stopper_thread (cpu=<optimized out>) at /home/zyj/Linux/linux-master/kernel/stop_machine.c:511 #31 0x8014de3c in smpboot_thread_fn (data=0x810c1c80) at /home/zyj/Linux/linux-master/kernel/smpboot.c:165 #32 0x8014a0dc in kthread (_create=0x810c1d40) at /home/zyj/Linux/linux-master/kernel/kthread.c:313 #33 0x80100150 in ret_from_fork () at /home/zyj/Linux/linux-master/arch/arm/kernel/entry-common.S:158 Backtrace stopped: previous frame identical to this frame (corrupt stack?)
See above #7~#15, there is a recursion in function pstore_ftrace_call(), and a spin_lock(lock=0x811a0f98) is hold since unlock operation in above #11 not finished. Then in above #0, trying to acquire same lock cause a deadlock.
Enabling 'record_ftrace' seems a basic operation of pstore/ftrace, Does it mean this feature is not available for a while?
Best Regards, Zheng
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