From: Daniel Henrique Barboza <danielhb413@gmail.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: Daniel Henrique Barboza <danielhb413@gmail.com>
Subject: [PATCH 1/1] hotplug-cpu.c: show 'last online CPU' error in dlpar_cpu_remove()
Date: Fri, 5 Mar 2021 14:38:45 -0300 [thread overview]
Message-ID: <20210305173845.451158-1-danielhb413@gmail.com> (raw)
Of all the reasons that dlpar_cpu_remove() can fail, the 'last online
CPU' is one that can be caused directly by the user offlining CPUs
in a partition/virtual machine that has hotplugged CPUs. Trying to
reclaim a hotplugged CPU can fail if the CPU is now the last online in
the system. This is easily reproduced using QEMU [1].
Throwing a more specific error message for this case, instead of just
"Failed to offline CPU", makes it clearer that the error is in fact a
known error situation instead of other generic/unknown cause.
[1] https://bugzilla.redhat.com/1911414
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
arch/powerpc/platforms/pseries/hotplug-cpu.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index 12cbffd3c2e3..134f393f09e1 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -514,7 +514,17 @@ static ssize_t dlpar_cpu_remove(struct device_node *dn, u32 drc_index)
rc = dlpar_offline_cpu(dn);
if (rc) {
- pr_warn("Failed to offline CPU %pOFn, rc: %d\n", dn, rc);
+ /* dlpar_offline_cpu will return -EBUSY from cpu_down() (via
+ * device_offline()) in 2 cases: cpu_hotplug_disable is true or
+ * there is only one CPU left. Warn the user about the second
+ * since this can happen with user offlining CPUs and then
+ * attempting hotunplugs.
+ */
+ if (rc == -EBUSY && num_online_cpus() == 1)
+ pr_warn("Unable to remove last online CPU %pOFn\n", dn);
+ else
+ pr_warn("Failed to offline CPU %pOFn, rc: %d\n", dn, rc);
+
return -EINVAL;
}
--
2.29.2
next reply other threads:[~2021-03-05 17:39 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-05 17:38 Daniel Henrique Barboza [this message]
2021-03-18 9:59 ` [PATCH 1/1] hotplug-cpu.c: show 'last online CPU' error in dlpar_cpu_remove() Daniel Henrique Barboza
2021-03-19 11:26 ` Michael Ellerman
2021-03-22 23:30 ` Daniel Henrique Barboza
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