[prev in list] [next in list] [prev in thread] [next in thread] 

List:       git-commits-head
Subject:    genirq/matrix: Deal with the sillyness of for_each_cpu() on UP
From:       Linux Kernel Mailing List <linux-kernel () vger ! kernel ! org>
Date:       2020-08-30 19:17:12
Message-ID: git-mailbomb-linux-master-784a0830377d0761834e385975bc46861fea9fa0 () kernel ! org
[Download RAW message or body]

Commit:     784a0830377d0761834e385975bc46861fea9fa0
Parent:     e027fffff799cdd70400c5485b1a54f482255985
Refname:    refs/heads/master
Web:        https://git.kernel.org/torvalds/c/784a0830377d0761834e385975bc46861fea9fa0
Author:     Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Sun Aug 30 19:07:53 2020 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun Aug 30 19:17:28 2020 +0200

    genirq/matrix: Deal with the sillyness of for_each_cpu() on UP
    
    Most of the CPU mask operations behave the same way, but for_each_cpu() and
    it's variants ignore the cpumask argument and claim that CPU0 is always in
    the mask. This is historical, inconsistent and annoying behaviour.
    
    The matrix allocator uses for_each_cpu() and can be called on UP with an
    empty cpumask. The calling code does not expect that this succeeds but
    until commit e027fffff799 ("x86/irq: Unbreak interrupt affinity setting")
    this went unnoticed. That commit added a WARN_ON() to catch cases which
    move an interrupt from one vector to another on the same CPU. The warning
    triggers on UP.
    
    Add a check for the cpumask being empty to prevent this.
    
    Fixes: 2f75d9e1c905 ("genirq: Implement bitmap matrix allocator")
    Reported-by: kernel test robot <rong.a.chen@intel.com>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: stable@vger.kernel.org
---
 kernel/irq/matrix.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/irq/matrix.c b/kernel/irq/matrix.c
index 30cc217b8631..651a4ad6d711 100644
--- a/kernel/irq/matrix.c
+++ b/kernel/irq/matrix.c
@@ -380,6 +380,13 @@ int irq_matrix_alloc(struct irq_matrix *m, const struct cpumask *msk,
 	unsigned int cpu, bit;
 	struct cpumap *cm;
 
+	/*
+	 * Not required in theory, but matrix_find_best_cpu() uses
+	 * for_each_cpu() which ignores the cpumask on UP .
+	 */
+	if (cpumask_empty(msk))
+		return -EINVAL;
+
 	cpu = matrix_find_best_cpu(m, msk);
 	if (cpu == UINT_MAX)
 		return -ENOSPC;
[prev in list] [next in list] [prev in thread] [next in thread]