The following commit has been merged into the x86/cache branch of tip: Commit-ID: dc433797c6f639e46824585bbf943578f13d54bf Gitweb: https://git.kernel.org/tip/dc433797c6f639e46824585bbf943578f13d54bf Author: Xiaochen Shen <xiaochen.shen@xxxxxxxxx> AuthorDate: Thu, 09 Jan 2020 00:13:46 +08:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Mon, 13 Jan 2020 14:10:21 +01:00 x86/resctrl: Do not reconfigure exiting tasks When writing a pid to file "tasks", a callback function move_myself() is queued to this task to be called when the task returns from kernel mode or exits. The purpose of move_myself() is to activate the newly assigned closid and/or rmid associated with this task. This activation is done by calling resctrl_sched_in() from move_myself(), the same function that is called when switching to this task. If this work is successfully queued but then the task enters PF_EXITING status (e.g., receiving signal SIGKILL, SIGTERM) prior to the execution of the callback move_myself(), move_myself() still calls resctrl_sched_in() since the task status is not currently considered. When a task is exiting, the data structure of the task itself will be freed soon. Calling resctrl_sched_in() to write the register that controls the task's resources is unnecessary and it implies extra performance overhead. Add check on task status in move_myself() and return immediately if the task is PF_EXITING. [ bp: Massage. ] Signed-off-by: Xiaochen Shen <xiaochen.shen@xxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx> Link: https://lkml.kernel.org/r/1578500026-21152-1-git-send-email-xiaochen.shen@xxxxxxxxx --- arch/x86/kernel/cpu/resctrl/rdtgroup.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c index 2e3b06d..205925d 100644 --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c @@ -532,11 +532,15 @@ static void move_myself(struct callback_head *head) kfree(rdtgrp); } + if (unlikely(current->flags & PF_EXITING)) + goto out; + preempt_disable(); /* update PQR_ASSOC MSR to make resource group go into effect */ resctrl_sched_in(); preempt_enable(); +out: kfree(callback); }
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