[tip: x86/urgent] x86/resctrl: Don't move a task to the same resource group
From: tip-bot2 for Fenghua Yu <hidden>
Date: 2021-01-08 08:19:28
Also in:
lkml
Subsystem:
rdt - resource allocation, the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Tony Luck, Reinette Chatre, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
The following commit has been merged into the x86/urgent branch of tip: Commit-ID: a0195f314a25582b38993bf30db11c300f4f4611 Gitweb: https://git.kernel.org/tip/a0195f314a25582b38993bf30db11c300f4f4611 Author: Fenghua Yu [off-list ref] AuthorDate: Thu, 17 Dec 2020 14:31:19 -08:00 Committer: Borislav Petkov [off-list ref] CommitterDate: Fri, 08 Jan 2021 09:08:03 +01:00 x86/resctrl: Don't move a task to the same resource group Shakeel Butt reported in [1] that a user can request a task to be moved to a resource group even if the task is already in the group. It just wastes time to do the move operation which could be costly to send IPI to a different CPU. Add a sanity check to ensure that the move operation only happens when the task is not already in the resource group. [1] https://lore.kernel.org/lkml/CALvZod7E9zzHwenzf7objzGKsdBmVwTgEJ0nPgs0LUFU3SN5Pw@mail.gmail.com/ (local) Fixes: e02737d5b826 ("x86/intel_rdt: Add tasks files") Reported-by: Shakeel Butt <redacted> Signed-off-by: Fenghua Yu <redacted> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Borislav Petkov <redacted> Reviewed-by: Tony Luck <tony.luck@intel.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/962ede65d8e95be793cb61102cca37f7bb018e66.1608243147.git.reinette.chatre@intel.com --- arch/x86/kernel/cpu/resctrl/rdtgroup.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 1c6f8a6..460f3e0 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c@@ -546,6 +546,13 @@ static void update_task_closid_rmid(struct task_struct *t) static int __rdtgroup_move_task(struct task_struct *tsk, struct rdtgroup *rdtgrp) { + /* If the task is already in rdtgrp, no need to move the task. */ + if ((rdtgrp->type == RDTCTRL_GROUP && tsk->closid == rdtgrp->closid && + tsk->rmid == rdtgrp->mon.rmid) || + (rdtgrp->type == RDTMON_GROUP && tsk->rmid == rdtgrp->mon.rmid && + tsk->closid == rdtgrp->mon.parent->closid)) + return 0; + /* * Set the task's closid/rmid before the PQR_ASSOC MSR can be * updated by them.