mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-25 02:09:42 +00:00
x86/resctrl: Use task_curr() instead of task_struct->on_cpu to prevent unnecessary IPI
[ Upstream commite0ad6dc896
] James reported in [1] that there could be two tasks running on the same CPU with task_struct->on_cpu set. Using task_struct->on_cpu as a test if a task is running on a CPU may thus match the old task for a CPU while the scheduler is running and IPI it unnecessarily. task_curr() is the correct helper to use. While doing so move the #ifdef check of the CONFIG_SMP symbol to be a C conditional used to determine if this helper should be used to ensure the code is always checked for correctness by the compiler. [1] https://lore.kernel.org/lkml/a782d2f3-d2f6-795f-f4b1-9462205fd581@arm.com Reported-by: James Morse <james.morse@arm.com> Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/e9e68ce1441a73401e08b641cc3b9a3cf13fe6d4.1608243147.git.reinette.chatre@intel.com Stable-dep-of:fe1f071438
("x86/resctrl: Fix task CLOSID/RMID update race") Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
parent
b3f9242467
commit
22c4eeafc3
1 changed files with 5 additions and 9 deletions
|
@ -2178,19 +2178,15 @@ static void rdt_move_group_tasks(struct rdtgroup *from, struct rdtgroup *to,
|
|||
t->closid = to->closid;
|
||||
t->rmid = to->mon.rmid;
|
||||
|
||||
#ifdef CONFIG_SMP
|
||||
/*
|
||||
* This is safe on x86 w/o barriers as the ordering
|
||||
* of writing to task_cpu() and t->on_cpu is
|
||||
* reverse to the reading here. The detection is
|
||||
* inaccurate as tasks might move or schedule
|
||||
* before the smp function call takes place. In
|
||||
* such a case the function call is pointless, but
|
||||
* If the task is on a CPU, set the CPU in the mask.
|
||||
* The detection is inaccurate as tasks might move or
|
||||
* schedule before the smp function call takes place.
|
||||
* In such a case the function call is pointless, but
|
||||
* there is no other side effect.
|
||||
*/
|
||||
if (mask && t->on_cpu)
|
||||
if (IS_ENABLED(CONFIG_SMP) && mask && task_curr(t))
|
||||
cpumask_set_cpu(task_cpu(t), mask);
|
||||
#endif
|
||||
}
|
||||
}
|
||||
read_unlock(&tasklist_lock);
|
||||
|
|
Loading…
Reference in a new issue