From: Menglong Dong <imagedong@xxxxxxxxxxx> While the system is running in KVM, pci config writing for virtio devices may cost long time(about 1-2ms), as it causes VM-exit. During __pci_bus_assign_resources(), pci_setup_bridge, which can do pci config writing up to 10 times, can be called many times without any _cond_resched(). So __pci_bus_assign_resources can cause 25+ms scheduling latency with !CONFIG_PREEMPT. To solve this problem, call _cond_resched() after pci config writing. Signed-off-by: Menglong Dong <imagedong@xxxxxxxxxxx> --- drivers/pci/access.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/pci/access.c b/drivers/pci/access.c index 46935695cfb9..babed43702df 100644 --- a/drivers/pci/access.c +++ b/drivers/pci/access.c @@ -57,6 +57,7 @@ int noinline pci_bus_write_config_##size \ pci_lock_config(flags); \ res = bus->ops->write(bus, devfn, pos, len, value); \ pci_unlock_config(flags); \ + _cond_resched(); \ return res; \ } -- 2.27.0
