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Subject[PATCH 3/5] x86/intel_rdt: Add diagnostics when writing the tasks file
Date
From: Tony Luck <tony.luck@intel.com>

About the only tricky case is trying to move a task into a monitor
group that is a subdirectory of a different control group. But cover
the simple cases too.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index 6a2cd89fa9de..c54189a1b54e 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -455,6 +455,7 @@ static int __rdtgroup_move_task(struct task_struct *tsk,
*/
atomic_dec(&rdtgrp->waitcount);
kfree(callback);
+ seq_buf_puts(&last_cmd_status, "task exited\n");
} else {
/*
* For ctrl_mon groups move both closid and rmid.
@@ -465,10 +466,13 @@ static int __rdtgroup_move_task(struct task_struct *tsk,
tsk->closid = rdtgrp->closid;
tsk->rmid = rdtgrp->mon.rmid;
} else if (rdtgrp->type == RDTMON_GROUP) {
- if (rdtgrp->mon.parent->closid == tsk->closid)
+ if (rdtgrp->mon.parent->closid == tsk->closid) {
tsk->rmid = rdtgrp->mon.rmid;
- else
+ } else {
+ seq_buf_puts(&last_cmd_status,
+ "Can't move task to different control group\n");
ret = -EINVAL;
+ }
}
}
return ret;
@@ -487,8 +491,11 @@ static int rdtgroup_task_write_permission(struct task_struct *task,
*/
if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
!uid_eq(cred->euid, tcred->uid) &&
- !uid_eq(cred->euid, tcred->suid))
+ !uid_eq(cred->euid, tcred->suid)) {
+ seq_buf_printf(&last_cmd_status,
+ "No permission to move task %d\n", task->pid);
ret = -EPERM;
+ }

put_cred(tcred);
return ret;
@@ -505,6 +512,7 @@ static int rdtgroup_move_task(pid_t pid, struct rdtgroup *rdtgrp,
tsk = find_task_by_vpid(pid);
if (!tsk) {
rcu_read_unlock();
+ seq_buf_printf(&last_cmd_status, "No task %d\n", pid);
return -ESRCH;
}
} else {
@@ -532,6 +540,7 @@ static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of,
if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
return -EINVAL;
rdtgrp = rdtgroup_kn_lock_live(of->kn);
+ seq_buf_clear(&last_cmd_status);

if (rdtgrp)
ret = rdtgroup_move_task(pid, rdtgrp, of);
--
2.11.0
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