Messages in this thread | | | Subject | Re: Fix 80d20d35af1e ("nohz: Fix local_timer_softirq_pending()") may have revealed another problem | From | Heiner Kallweit <> | Date | Fri, 28 Dec 2018 07:34:10 +0100 |
| |
On 28.12.2018 02:31, Frederic Weisbecker wrote: > On Fri, Dec 28, 2018 at 12:11:12AM +0100, Heiner Kallweit wrote: >> [...] > > Interesting, the softirq is raised from hardirq but it's not handled in the end of > the IRQ. Are you running threaded IRQS by any chance? If so I would expect ksoftirqd > to handle the pending work before we go idle. However I can imagine a small window > where such an expectation may not be met: if the softirq is raised after the ksoftirqd > thread is parked (CPUHP_AP_SMPBOOT_THREADS), which is right before we disable the CPU > (CPUHP_TEARDOWN_CPU). > I have a network driver (r8169) using NAPI which runs in softirq context AFAIK. For testing purposes I sometimes trigger system suspend via network, so there is network adapter activity when system suspends. Apart from that nothing really exciting: CPU0 CPU1 CPU2 CPU3 0: 43 0 0 0 IO-APIC 2-edge timer 1: 4 0 0 0 IO-APIC 1-edge i8042 8: 0 1 0 0 IO-APIC 8-fasteoi rtc0 9: 0 0 0 0 IO-APIC 9-fasteoi acpi 12: 0 0 0 5 IO-APIC 12-edge i8042 120: 0 0 0 0 PCI-MSI 311296-edge PCIe PME 121: 0 0 0 0 PCI-MSI 315392-edge PCIe PME 122: 0 0 0 0 PCI-MSI 327680-edge PCIe PME 123: 0 0 3328 0 PCI-MSI 294912-edge ahci[0000:00:12.0] 124: 0 133 0 0 PCI-MSI 344064-edge xhci_hcd 125: 0 0 32 0 PCI-MSI 245760-edge mei_me 127: 381 0 0 0 PCI-MSI 1572864-edge enp3s0 128: 0 0 0 236 PCI-MSI 32768-edge i915 129: 0 374 0 0 PCI-MSI 229376-edge snd_hda_intel:card0
> I don't know if we can afford to ignore a softirq even at this late stage. We should > probably avoid leaking any. So here is a possible fix, if you don't mind trying: > I tested your patch and at least in the first minutes of testing couldn't reproduce the issue any longer. I tested manual system suspend and the following script you sent when we started to analyze the issue.
Heiner
--------------------------------------------------------------------------
#!/bin/bash
do_hotplug() { for i in $(seq 1 $2) do echo $1 > /sys/devices/system/cpu/cpu$i/online done }
LAST_CPU=$(($(nproc)-1))
while true do do_hotplug 0 $LAST_CPU do_hotplug 1 $LAST_CPU done
| |