linux-kernel - Re: [PATCH v5 1/8] x86/resctrl: Add multiple tasks to the resctrl group at once

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Message-ID: <78cf154c-e9e3-a3be-c52b-d70ff4df8be2@amd.com>
Date:   Tue, 11 Jul 2023 12:54:40 -0500
From:   "Moger, Babu" <babu.moger@....com>
To:     Reinette Chatre <reinette.chatre@...el.com>, corbet@....net,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de
Cc:     fenghua.yu@...el.com, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, paulmck@...nel.org, akpm@...ux-foundation.org,
        quic_neeraju@...cinc.com, rdunlap@...radead.org,
        damien.lemoal@...nsource.wdc.com, songmuchun@...edance.com,
        peterz@...radead.org, jpoimboe@...nel.org, pbonzini@...hat.com,
        chang.seok.bae@...el.com, pawan.kumar.gupta@...ux.intel.com,
        jmattson@...gle.com, daniel.sneddon@...ux.intel.com,
        sandipan.das@....com, tony.luck@...el.com, james.morse@....com,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        bagasdotme@...il.com, eranian@...gle.com,
        christophe.leroy@...roup.eu, jarkko@...nel.org,
        adrian.hunter@...el.com, quic_jiles@...cinc.com,
        peternewman@...gle.com
Subject: Re: [PATCH v5 1/8] x86/resctrl: Add multiple tasks to the resctrl
 group at once

Hi Reinette,

On 7/7/23 16:38, Reinette Chatre wrote:
> Hi Babu,
> 
> On 6/1/2023 12:00 PM, Babu Moger wrote:
>> The resctrl task assignment for monitor or control group needs to be
>> done one at a time. For example:
>>
>>   $mount -t resctrl resctrl /sys/fs/resctrl/
>>   $mkdir /sys/fs/resctrl/ctrl_grp1
>>   $echo 123 > /sys/fs/resctrl/ctrl_grp1/tasks
>>   $echo 456 > /sys/fs/resctrl/ctrl_grp1/tasks
>>   $echo 789 > /sys/fs/resctrl/ctrl_grp1/tasks
>>
>> This is not user-friendly when dealing with hundreds of tasks.
>>
>> Support multiple task assignment in one command with tasks ids separated
>> by commas. For example:
>>   $echo 123,456,789 > /sys/fs/resctrl/ctrl_grp1/tasks
>>
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 6ad33f355861..504137a5d31f 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -696,11 +696,10 @@ static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of,
>>  				    char *buf, size_t nbytes, loff_t off)
>>  {
>>  	struct rdtgroup *rdtgrp;
>> +	char *pid_str;
>>  	int ret = 0;
>>  	pid_t pid;
>>  
>> -	if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
>> -		return -EINVAL;
>>  	rdtgrp = rdtgroup_kn_lock_live(of->kn);
>>  	if (!rdtgrp) {
>>  		rdtgroup_kn_unlock(of->kn);
>> @@ -708,16 +707,27 @@ static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of,
>>  	}
>>  	rdt_last_cmd_clear();
>>  
>> -	if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED ||
>> -	    rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
>> -		ret = -EINVAL;
>> -		rdt_last_cmd_puts("Pseudo-locking in progress\n");
>> -		goto unlock;
>> -	}
> 
> Please do not drop this snippet. I think there may have been misunderstanding
> during previous comments - this snippet is required, it just does not need
> to be run for every pid the user provides since it depends on the resource
> group, not the pid.

Ok. Got it.

> 
>> +	while (buf && buf[0] != '\0') {
> 
> I think it may help to add a check for '\n' here also. It looks to me
> that a user (shell) that provides "pid,", which is "pid,\n" would encounter
> error and this may not actually be an error.

Ok Sounds good. I have verified it. New check will look like this below.

while (buf && buf[0] != '\0' && buf[0] != '\n') {

> 
>> +		pid_str = strim(strsep(&buf, ","));
>>  
>> -	ret = rdtgroup_move_task(pid, rdtgrp, of);
>> +		if (kstrtoint(pid_str, 0, &pid)) {
>> +			rdt_last_cmd_puts("Task list parsing error\n");
>> +			ret = -EINVAL;
>> +			break;
>> +		}
>>  
>> -unlock:
>> +		if (pid < 0) {
>> +			rdt_last_cmd_printf("Invalid pid %d value\n", pid);
>> +			ret = -EINVAL;
>> +			break;
>> +		}
> 
> I'm trying to image a possible error and it does not look right. For example,
> the above could be "Invalid pid 123 value". How about just "Invalid pid %d".

Sure.

Thanks
Babu