From: Valentin Schneider <valentin.schnei...@arm.com>
A CPU's current task can have its {closid, rmid} fields read locally while
they are being concurrently written to from another CPU. This can happen
anytime __resctrl_sched_in() races with either __rdtgroup_move_task() or
rdt_move_group_tasks().
Prevent load / store tearing for those accesses by giving them the
READ_ONCE() / WRITE_ONCE() treatment.
Signed-off-by: Valentin Schneider <valentin.schnei...@arm.com>
Signed-off-by: Reinette Chatre <reinette.cha...@intel.com>
---
V1->V2:
* Subject line prefix x86/intel_rdt -> x86/resctrl. (Reinette)
arch/x86/include/asm/resctrl.h | 11 +++++++----
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 10 +++++-----
2 files changed, 12 insertions(+), 9 deletions(-)
diff --git a/arch/x86/include/asm/resctrl.h b/arch/x86/include/asm/resctrl.h
index 07603064df8f..d60ed0668a59 100644
--- a/arch/x86/include/asm/resctrl.h
+++ b/arch/x86/include/asm/resctrl.h
@@ -56,19 +56,22 @@ static void __resctrl_sched_in(void)
struct resctrl_pqr_state *state = this_cpu_ptr(&pqr_state);
u32 closid = state->default_closid;
u32 rmid = state->default_rmid;
+ u32 tmp;
/*
* If this task has a closid/rmid assigned, use it.
* Else use the closid/rmid assigned to this cpu.
*/
if (static_branch_likely(&rdt_alloc_enable_key)) {
- if (current->closid)
- closid = current->closid;
+ tmp = READ_ONCE(current->closid);
+ if (tmp)
+ closid = tmp;
}
if (static_branch_likely(&rdt_mon_enable_key)) {
- if (current->rmid)
- rmid = current->rmid;
+ tmp = READ_ONCE(current->rmid);
+ if (tmp)
+ rmid = tmp;
}
if (closid != state->cur_closid || rmid != state->cur_rmid) {
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 9bd36210d220..5aeb4fb91228 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -569,11 +569,11 @@ static int __rdtgroup_move_task(struct task_struct *tsk,
*/
if (rdtgrp->type == RDTCTRL_GROUP) {
- tsk->closid = rdtgrp->closid;
- tsk->rmid = rdtgrp->mon.rmid;
+ WRITE_ONCE(tsk->closid, rdtgrp->closid);
+ WRITE_ONCE(tsk->rmid, rdtgrp->mon.rmid);
} else if (rdtgrp->type == RDTMON_GROUP) {
if (rdtgrp->mon.parent->closid == tsk->closid) {
- tsk->rmid = rdtgrp->mon.rmid;
+ WRITE_ONCE(tsk->rmid, rdtgrp->mon.rmid);
} else {
rdt_last_cmd_puts("Can't move task to different control
group\n");
return -EINVAL;
@@ -2316,8 +2316,8 @@ static void rdt_move_group_tasks(struct rdtgroup *from,
struct rdtgroup *to,
for_each_process_thread(p, t) {
if (!from || is_closid_match(t, from) ||
is_rmid_match(t, from)) {
- t->closid = to->closid;
- t->rmid = to->mon.rmid;
+ WRITE_ONCE(t->closid, to->closid);
+ WRITE_ONCE(t->rmid, to->mon.rmid);
/*
* If the task is on a CPU, set the CPU in the mask.
--
2.26.2
