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

[Moger, Babu]

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@xxxxxxx>
>> ---
>> 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