[PATCH] smtstate: Start smtstate service after network target

[Srikar Dronamraju]

While setting smtstate on boot, pc64_cpu may fail to set smt mode if there
is pci probe happening which disables cpu hotplug.

smtstate[14016]: /sys/devices/system/cpu/smt/control: Device or resource busy
smtstate[14017]: Error updating SMT=4
systemd[1]: smtstate.service: Main process exited, code=exited, status=1/FAILURE
systemd[1]: smtstate.service: Failed with result 'exit-code'.
systemd[1]: Failed to start SMT automatic initialization service.

Here are traces from cpu_down_maps_locked showing cpu_hotplug_disabled=1
and cpu_down_maps_locked returning -EBUSY causing ppc64_cpu command to
fail while setting smt mode.

ppc64_cpu 6302 [037] 19.370155: probe:cpu_down_maps_locked: (c000000000160b18) cpu_hotplug_disabled=1
ppc64_cpu 6302 [037] 19.370164: probe:cpu_down_maps_locked__return: (c000000000160b18 <- c000000000162508) retval=0xfffffffffffffff0

At the time of ppc64_cpu failure, tracing cpu_hotplug_enable() shows the
likely reason why cpu_hotplug_disabled=1 (A network driver was trying to
probe a pci device).

(udev-worker) 5478 [016] 19.613108: probe:cpu_hotplug_enable: (c00000000015dba8)
c00000000015dba8 cpu_hotplug_enable+0x8 (/boot/vmlinux)
c0000000008fa7a8 pci_device_probe+0x1f8 (/boot/vmlinux)
c000000000a02440 really_probe+0x2f0 (/boot/vmlinux)
c000000000a0294c __driver_probe_device+0x1bc (/boot/vmlinux)
c000000000a029f0 driver_probe_device+0x60 (/boot/vmlinux)
c000000000a031f8 __driver_attach+0xf8 (/boot/vmlinux)
c0000000009fead4 bus_for_each_dev+0xb4 (/boot/vmlinux)
c000000000a01744 driver_attach+0x34 (/boot/vmlinux)
c000000000a00b18 bus_add_driver+0x218 (/boot/vmlinux)
c000000000a04278 driver_register+0x98 (/boot/vmlinux)
c0000000008f7d68 __pci_register_driver+0x68 (/boot/vmlinux)
c0080000fb98ee7c [unknown] ([i40e])
c000000000012690 do_one_initcall+0x60 (/boot/vmlinux)
c00000000027af94 do_init_module+0x84 (/boot/vmlinux)
c000000000278c0c load_module+0x2bfc (/boot/vmlinux)
c0000000002798e0 __do_sys_init_module+0x210 (/boot/vmlinux)

Hence to make smtstate more robust, this change ensures smtstate.service
is only called after network initialization and hence avoid all other
instances which could be disabling cpu_hotlug_disabled.

Suggested-by: "Nysal Jan K.A" <ny...@linux.ibm.com>
Suggested-by: Shrikanth Hegde <ssh...@linux.ibm.com>
Signed-off-by: Srikar Dronamraju <sri...@linux.ibm.com>
---
systemd/smtstate.service.in | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/systemd/smtstate.service.in b/systemd/smtstate.service.in
index c2853650c51a..ba3f3d3a9f29 100644
--- a/systemd/smtstate.service.in
+++ b/systemd/smtstate.service.in
@@ -3,7 +3,7 @@ Description=SMT automatic initialization service
Documentation=man:smtstate(8)
Conflicts=shutdown.target
Before=shutdown.target
-After=sysinit.target
+After=network.target
DefaultDependencies=no

[Service]
--
2.49.0