[Crash-utility] [PATCH] Fix machdep->HZ calculation for kernel versions > 2.6.0

[lijiang]

在 2021年04月23日 17:44, HAGIO KAZUHITO(萩尾　一仁) 写道:
> -----Original Message-----
>>> As for the 'write_expire' way, I found that it can be printed after
>>> "set scope dd_init_queue" or "set scope deadline_init_queue" on old kernels.
>>>
>>> crash> p write_expire
>>> No symbol "write_expire" in current context.
>>> p: gdb request failed: p write_expire
>>> crash> set scope dd_init_queue
>>> scope: ffffffffa43e3f80 (dd_init_queue)
>>> crash> p write_expire
>>> $1 = 5000
>>>
>>> Maybe we can make use of gdb_set_crash_scope() and gdb_pass_through() to
>>> get this value?
>>>
>>
>> The 'write_expire' is a static variable, which needs to get its value from
>> gdb. Seems that it is a bit complicated.
>>
>> But It's worth having a try.
> 
> The following is a draft patch.  It worked for some dumpfiles I have
> from 2.6.16 to 5.11 including RHEL8.0 one.  What do you think?
> 

Good idea. Could you please post a formal patch about this change?

BTW: is that possible to remove the 'cfq_slice_async'?

Thanks.
Lianbo

> diff --git a/task.c b/task.c
> index 423cd454502b..654df6b1220c 100644
> --- a/task.c
> +++ b/task.c
> @@ -417,7 +417,33 @@ task_init(void)
>  
>  	STRUCT_SIZE_INIT(cputime_t, "cputime_t");
>  
> -	if (symbol_exists("cfq_slice_async")) {
> +	if ((symbol_exists("dd_init_queue") &&
> +	    gdb_set_crash_scope(symbol_value("dd_init_queue"), "dd_init_queue")) ||
> +	    (symbol_exists("deadline_init_queue") &&
> +	    gdb_set_crash_scope(symbol_value("deadline_init_queue"), "deadline_init_queue"))) {
> +		char buf[BUFSIZE];
> +		uint write_expire = 0;
> +
> +		open_tmpfile();
> +		sprintf(buf, "printf \"%%d\", write_expire");
> +		if (gdb_pass_through(buf, pc->tmpfile, GNU_RETURN_ON_ERROR)) {
> +			rewind(pc->tmpfile);
> +			while (fgets(buf, BUFSIZE, pc->tmpfile)) {
> +				sscanf(buf, "%d", &write_expire);
> +			}
> +		}
> +		close_tmpfile();
> +
> +		if (write_expire) {
> +			machdep->hz = write_expire / 5;
> +			if (CRASHDEBUG(2))
> +				fprintf(fp, "write_expire exists: setting hz to %d\n",
> +					machdep->hz);
> +		}
> +		fprintf(fp, "write_expire = %d, machdep->hz = %d\n", write_expire, machdep->hz);
> +		gdb_set_crash_scope(0, NULL);
> +
> +	} else if (symbol_exists("cfq_slice_async")) {
>  		uint cfq_slice_async;
>  
>  		get_symbol_data("cfq_slice_async", sizeof(int),
>