Affinity change can happen in both interrupt context and non-interrupt context. The paranoia check for interrupt target cpu is not always true in non-interrupt context.
For example: Set affinity for irq to CPU#7 $ echo 80 > /proc/irq/default_smp_affinity
Open serial port on different CPU. $taskset -c 4 agetty -L 115200 ttyS1
Will triger the following warning.
WARNING: CPU: 4 PID: 765 at arch/x86/kernel/apic/msi.c:75 msi_set_affinity+0x16f/0x190 Call Trace: irq_do_set_affinity+0x57/0x1b0 irq_setup_affinity+0x136/0x190 irq_startup+0xaf/0xf0 __setup_irq+0x745/0x7e0 ? kmem_cache_alloc_trace+0x2b5/0x450 request_threaded_irq+0x110/0x180 univ8250_setup_irq+0x1e2/0x220 serial8250_do_startup+0x481/0x760 serial8250_startup+0x1e/0x20 uart_startup.part.22+0xf8/0x260 uart_port_activate+0x41/0x60 tty_port_open+0x82/0xd0 ? _raw_spin_unlock+0x16/0x30 uart_open+0x1e/0x30 tty_open+0x100/0x4d0 ? cdev_purge+0x60/0x60 chrdev_open+0xa3/0x1c0 ? cdev_put.part.3+0x20/0x20 do_dentry_open+0x21f/0x380 vfs_open+0x2f/0x40 path_openat+0xd67/0xf60 ? page_add_file_rmap+0xad/0x140 ? do_set_pte+0xd7/0x210 do_filp_open+0xc5/0x140 do_sys_openat2+0x239/0x300 ? do_sys_openat2+0x239/0x300 do_sys_open+0x59/0x80 __x64_sys_openat+0x20/0x30 do_syscall_64+0x3f/0x90 entry_SYSCALL_64_after_hwframe+0x44/0xae
With this patch, the warning is only reported in interrupt context and when the target CPU is not local CPU.
Signed-off-by: Yongxin Liu yongxin.liu@windriver.com --- arch/x86/kernel/apic/msi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kernel/apic/msi.c b/arch/x86/kernel/apic/msi.c index 44ebe25e7703..c4c73f227eeb 100644 --- a/arch/x86/kernel/apic/msi.c +++ b/arch/x86/kernel/apic/msi.c @@ -72,7 +72,7 @@ msi_set_affinity(struct irq_data *irqd, const struct cpumask *mask, bool force) * Paranoia: Validate that the interrupt target is the local * CPU. */ - if (WARN_ON_ONCE(cpu != smp_processor_id())) { + if (in_interrupt() && WARN_ON_ONCE(cpu != smp_processor_id())) { irq_msi_update_msg(irqd, cfg); return ret; }