Re: [PATCH] blk-iocost: initialize rqos before accessing it

[Breno Leitao]

Hello Michal,

On 2/24/23 18:51, Michal Koutný wrote:
> > 	blk_iocost_init (include/asm-generic/qspinlock.h:128
> > 			 include/linux/spinlock.h:203
> > 			 include/linux/spinlock_api_smp.h:158
> > 			 include/linux/spinlock.h:400
> > 			 block/blk-iocost.c:2884)
> > 	ioc_qos_write (block/blk-iocost.c:3198)
> > 	? kretprobe_perf_func (kernel/trace/trace_kprobe.c:1566)
> > 	? kernfs_fop_write_iter (include/linux/slab.h:584 fs/kernfs/file.c:311)
> > 	? __kmem_cache_alloc_node (mm/slab.h:? mm/slub.c:3452 mm/slub.c:3491)
> > 	? _copy_from_iter (arch/x86/include/asm/uaccess_64.h:46
> > 			   arch/x86/include/asm/uaccess_64.h:52
> > 			   lib/iov_iter.c:183 lib/iov_iter.c:628)
> > 	? kretprobe_dispatcher (kernel/trace/trace_kprobe.c:1693)
> > 	cgroup_file_write (kernel/cgroup/cgroup.c:4061)
> > 	kernfs_fop_write_iter (fs/kernfs/file.c:334)
> > 	vfs_write (include/linux/fs.h:1849 fs/read_write.c:491
> > 		   fs/read_write.c:584)
> > 	ksys_write (fs/read_write.c:637)
> > 	do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80)
> > 	entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120)
>
> BTW, out of curiosity what tool did you use to list stack with line
> numbers?

I use the decode_stacktrace.sh from kernel's scripts directory. You 
basically
pipe the stack to it, and call it passing the vmlinux file. It is 
incredible handy.

https://elixir.bootlin.com/linux/latest/source/scripts/decode_stacktrace.sh

Thanks for the review,
Breno