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    SubjectRe: [PATCH v5 1/8] x86/resctrl: Add multiple tasks to the resctrl group at once
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    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@amd.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.

    > + 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.

    > + 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".

    > +
    > + ret = rdtgroup_move_task(pid, rdtgrp, of);
    > + if (ret) {
    > + rdt_last_cmd_printf("Error while processing task %d\n", pid);
    > + break;
    > + }
    > + }
    > rdtgroup_kn_unlock(of->kn);
    >
    > return ret ?: nbytes;
    >
    >

    Reinette

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