Re: [PATCH] percpu: improve percpu_alloc_percpu event trace

[Vasily Averin]

On 5/6/22 23:38, kernel test robot wrote:
>>> include/trace/events/percpu.h:11:1: sparse: sparse: cast from restricted gfp_t
>>> include/trace/events/percpu.h:11:1: sparse: sparse: incorrect type in argument 3 (different base types) @@     expected unsigned long flags @@     got restricted gfp_t [usertype] gfp_flags @@
>    include/trace/events/percpu.h:11:1: sparse:     expected unsigned long flags
>    include/trace/events/percpu.h:11:1: sparse:     got restricted gfp_t [usertype] gfp_flags
>    mm/percpu.c: note: in included file (through include/trace/trace_events.h, include/trace/define_trace.h, include/trace/events/percpu.h):
>>> include/trace/events/percpu.h:11:1: sparse: sparse: cast to restricted gfp_t
>>> include/trace/events/percpu.h:11:1: sparse: sparse: cast to restricted gfp_t
>>> include/trace/events/percpu.h:11:1: sparse: sparse: restricted gfp_t degrades to integer
>>> include/trace/events/percpu.h:11:1: sparse: sparse: restricted gfp_t degrades to integer
>    mm/percpu.c:2012:24: sparse: sparse: context imbalance in 'pcpu_balance_free' - unexpected unlock

The same messages are generated for any other gfp_t argument in trace events.
As far as I understand it is not a bug per se,
but trace macros lacks __force attribute in 'gfp_t'-> 'unsigned long' casts.
The same thing happens with mode_t and with some other places using __print_flags()
for __bitwise marked types.

I can make sparse happy, here and elsewhere but it requires a lot of __force attributes.
Is anyone interested in such patches, or can we silently ignore these messages?

Need to add __force attribute to all entries in __def_gfpflag_names array
and add few changes into trace description, below is an example.

> vim +11 include/trace/events/percpu.h
> 
> df95e795a72289 Dennis Zhou   2017-06-19  10  
> df95e795a72289 Dennis Zhou   2017-06-19 @11  TRACE_EVENT(percpu_alloc_percpu,
> df95e795a72289 Dennis Zhou   2017-06-19  12  
> df95e795a72289 Dennis Zhou   2017-06-19  13  	TP_PROTO(bool reserved, bool is_atomic, size_t size,
> dee6876db0a7a4 Vasily Averin 2022-05-06  14  		 size_t align, void *base_addr, int off,
> dee6876db0a7a4 Vasily Averin 2022-05-06  15  		 void __percpu *ptr, size_t bytes_alloc, gfp_t gfp_flags),
> df95e795a72289 Dennis Zhou   2017-06-19  16  
> dee6876db0a7a4 Vasily Averin 2022-05-06  17  	TP_ARGS(reserved, is_atomic, size, align, base_addr, off, ptr,
> dee6876db0a7a4 Vasily Averin 2022-05-06  18  		bytes_alloc, gfp_flags),
> df95e795a72289 Dennis Zhou   2017-06-19  19  
> df95e795a72289 Dennis Zhou   2017-06-19  20  	TP_STRUCT__entry(
> df95e795a72289 Dennis Zhou   2017-06-19  21  		__field(	bool,			reserved	)
> df95e795a72289 Dennis Zhou   2017-06-19  22  		__field(	bool,			is_atomic	)
> df95e795a72289 Dennis Zhou   2017-06-19  23  		__field(	size_t,			size		)
> df95e795a72289 Dennis Zhou   2017-06-19  24  		__field(	size_t,			align		)
> df95e795a72289 Dennis Zhou   2017-06-19  25  		__field(	void *,			base_addr	)
> df95e795a72289 Dennis Zhou   2017-06-19  26  		__field(	int,			off		)
> df95e795a72289 Dennis Zhou   2017-06-19  27  		__field(	void __percpu *,	ptr		)
> dee6876db0a7a4 Vasily Averin 2022-05-06  28  		__field(	size_t,			bytes_alloc	)
> dee6876db0a7a4 Vasily Averin 2022-05-06  29  		__field(	gfp_t,			gfp_flags	)
VvS: need to replace gfp_t to unsigned long ...

> df95e795a72289 Dennis Zhou   2017-06-19  30  	),
> df95e795a72289 Dennis Zhou   2017-06-19  31  	TP_fast_assign(
> df95e795a72289 Dennis Zhou   2017-06-19  32  		__entry->reserved	= reserved;
> df95e795a72289 Dennis Zhou   2017-06-19  33  		__entry->is_atomic	= is_atomic;
> df95e795a72289 Dennis Zhou   2017-06-19  34  		__entry->size		= size;
> df95e795a72289 Dennis Zhou   2017-06-19  35  		__entry->align		= align;
> df95e795a72289 Dennis Zhou   2017-06-19  36  		__entry->base_addr	= base_addr;
> df95e795a72289 Dennis Zhou   2017-06-19  37  		__entry->off		= off;
> df95e795a72289 Dennis Zhou   2017-06-19  38  		__entry->ptr		= ptr;
> dee6876db0a7a4 Vasily Averin 2022-05-06  39  		__entry->bytes_alloc	= bytes_alloc;
> dee6876db0a7a4 Vasily Averin 2022-05-06  40  		__entry->gfp_flags	= gfp_flags;
VvS: ... and use here (__force unsigned long)

> df95e795a72289 Dennis Zhou   2017-06-19  41  	),
> df95e795a72289 Dennis Zhou   2017-06-19  42  
> dee6876db0a7a4 Vasily Averin 2022-05-06  43  	TP_printk("reserved=%d is_atomic=%d size=%zu align=%zu base_addr=%p off=%d ptr=%p bytes_alloc=%zu gfp_flags=%s",
> df95e795a72289 Dennis Zhou   2017-06-19  44  		  __entry->reserved, __entry->is_atomic,
> df95e795a72289 Dennis Zhou   2017-06-19  45  		  __entry->size, __entry->align,
> dee6876db0a7a4 Vasily Averin 2022-05-06  46  		  __entry->base_addr, __entry->off, __entry->ptr,
> dee6876db0a7a4 Vasily Averin 2022-05-06  47  		  __entry->bytes_alloc, show_gfp_flags(__entry->gfp_flags))
> df95e795a72289 Dennis Zhou   2017-06-19  48  );
> df95e795a72289 Dennis Zhou   2017-06-19  49  
 Thank you,
	Vasily Averin