linux-kernel - Re: [External] Re: [RFC 02/12] perf event action: Add parsing const expr support

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Message-ID: <bbeba4c6-6c46-4708-9ce9-ff6037fe6449@bytedance.com>
Date: Wed, 4 Dec 2024 16:29:08 +0800
From: Yang Jihong <yangjihong@...edance.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: peterz@...radead.org, mingo@...hat.com, namhyung@...nel.org,
 mark.rutland@....com, alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
 irogers@...gle.com, adrian.hunter@...el.com, kan.liang@...ux.intel.com,
 james.clark@....com, linux-perf-users@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [RFC 02/12] perf event action: Add parsing const
 expr support

Hello,

On 11/29/24 04:23, Arnaldo Carvalho de Melo wrote:
> On Thu, Nov 28, 2024 at 09:35:43PM +0800, Yang Jihong wrote:
>> Event action requires constant expression parsing support,
>> which include constant integer and constant string.
>>
>> Signed-off-by: Yang Jihong <yangjihong@...edance.com>
>> ---
>>   tools/perf/util/parse-action.c | 27 +++++++++++++++++++++++++++
>>   tools/perf/util/parse-action.h |  5 +++++
>>   2 files changed, 32 insertions(+)
>>
>> diff --git a/tools/perf/util/parse-action.c b/tools/perf/util/parse-action.c
>> index 01c8c7fdea59..391546bf3d73 100644
>> --- a/tools/perf/util/parse-action.c
>> +++ b/tools/perf/util/parse-action.c
>> @@ -4,6 +4,9 @@
>>    * Actions are the programs that run when the sampling event is triggered.
>>    * The action is a list of expressions separated by semicolons (;).
>>    * Each action is an expression, added to actions_head node as list_head node.
>> + *
>> + * Supported expressions:
>> + *   - constant:
> 
> This seems incomplete, what should come after the :?
> 
> the patch description, at the beginning of this message has more details
> than here.
This patch only implements a general constant expression category. The 
next patch will support parsing of specific string constant expressions 
and integer constant expressions.


> 
>>    */
>>   
>>   #include "util/debug.h"
>> @@ -115,7 +118,31 @@ void event_actions__free(void)
>>   	(void)event_actions__for_each_expr_safe(do_action_free, NULL, false);
>>   }
>>   
>> +static struct evtact_expr_ops *expr_const_ops_list[EVTACT_EXPR_CONST_TYPE_MAX] = {
>> +};
>> +
>> +static int expr_const_set_ops(struct evtact_expr *expr, u32 opcode)
>> +{
>> +	if (opcode >= EVTACT_EXPR_CONST_TYPE_MAX) {
>> +		pr_err("expr_const opcode invalid: %u\n", opcode);
>> +		return -EINVAL;
>> +	}
>> +
>> +	if (expr_const_ops_list[opcode] == NULL) {
>> +		pr_err("expr_const opcode not supported: %u\n", opcode);
>> +		return -ENOTSUP;
>> +	}
> 
> Since expr_const_ops_list[EVTACT_EXPR_TYPE_CONST] is NULL, this will
> always fail?
> 
Yes, this patch does not support specific constant expressions, so it is 
empty.

Thanks,
Yang.