powerpc/pseries: safely roll back failed DLPAR cpu add

dlpar_online_cpu() attempts to online all threads of a core that has
been added to an LPAR. If onlining a non-primary thread
fails (e.g. due to an allocation failure), the core is left with at
least one thread online. dlpar_cpu_add() attempts to roll back the
whole operation, releasing the core back to the platform. However,
since some threads of the core being removed are still online, the
BUG_ON(cpu_online(cpu)) in pseries_remove_processor() strikes:

LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
Modules linked in:
CPU: 3 PID: 8587 Comm: drmgr Not tainted 5.3.0-rc2-00190-g9b123d1ea237-dirty #46
NIP:  c0000000000eeb2c LR: c0000000000eeac4 CTR: c0000000000ee9e0
REGS: c0000001f745b6c0 TRAP: 0700   Not tainted  (5.3.0-rc2-00190-g9b123d1ea237-dirty)
MSR:  800000010282b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE,TM[E]>  CR: 44002448  XER: 00000000
CFAR: c00000000195d718 IRQMASK: 0
GPR00: c0000000000eeac4 c0000001f745b950 c0000000032f6200 0000000000000008
GPR04: 0000000000000008 c000000003349c78 0000000000000040 00000000000001ff
GPR08: 0000000000000008 0000000000000000 0000000000000001 0007ffffffffffff
GPR12: 0000000084002844 c00000001ecacb80 0000000000000000 0000000000000000
GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000008
GPR24: c000000003349ee0 c00000000334a2e4 c0000000fca4d7a8 c000000001d20048
GPR28: 0000000000000001 ffffffffffffffff ffffffffffffffff c0000000fca4d7c4
NIP [c0000000000eeb2c] pseries_smp_notifier+0x14c/0x2e0
LR [c0000000000eeac4] pseries_smp_notifier+0xe4/0x2e0
Call Trace:
[c0000001f745b950] [c0000000000eeac4] pseries_smp_notifier+0xe4/0x2e0 (unreliable)
[c0000001f745ba10] [c0000000001ac774] notifier_call_chain+0xb4/0x190
[c0000001f745bab0] [c0000000001ad62c] blocking_notifier_call_chain+0x7c/0xb0
[c0000001f745baf0] [c00000000167bda0] of_detach_node+0xc0/0x110
[c0000001f745bb50] [c0000000000e7ae4] dlpar_detach_node+0x64/0xa0
[c0000001f745bb80] [c0000000000edefc] dlpar_cpu_add+0x31c/0x360
[c0000001f745bc10] [c0000000000ee980] dlpar_cpu_probe+0x50/0xb0
[c0000001f745bc50] [c00000000002cf70] arch_cpu_probe+0x40/0x70
[c0000001f745bc70] [c000000000ccd808] cpu_probe_store+0x48/0x80
[c0000001f745bcb0] [c000000000cbcef8] dev_attr_store+0x38/0x60
[c0000001f745bcd0] [c00000000059c980] sysfs_kf_write+0x70/0xb0
[c0000001f745bd10] [c00000000059afb8] kernfs_fop_write+0xf8/0x280
[c0000001f745bd60] [c0000000004b437c] __vfs_write+0x3c/0x70
[c0000001f745bd80] [c0000000004b8710] vfs_write+0xd0/0x220
[c0000001f745bdd0] [c0000000004b8acc] ksys_write+0x7c/0x140
[c0000001f745be20] [c00000000000bbd8] system_call+0x5c/0x68

Move dlpar_offline_cpu() up in the file so that dlpar_online_cpu() can
use it to re-offline any threads that have been onlined when an error
is encountered.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Fixes: e666ae0b10aa ("powerpc/pseries: Update CPU hotplug error recovery")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191016183611.10867-3-nathanl@linux.ibm.com

diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index f3f54ef645e124dd886f5c7fae7d4f8e57c00990..8ab24bd7f89c659e1aebd2d91bf2873a8c703b23 100644 (file)
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -338,6 +338,62 @@ static void pseries_remove_processor(struct device_node *np)
        cpu_maps_update_done();
 }
 
+static int dlpar_offline_cpu(struct device_node *dn)
+{
+       int rc = 0;
+       unsigned int cpu;
+       int len, nthreads, i;
+       const __be32 *intserv;
+       u32 thread;
+
+       intserv = of_get_property(dn, "ibm,ppc-interrupt-server#s", &len);
+       if (!intserv)
+               return -EINVAL;
+
+       nthreads = len / sizeof(u32);
+
+       cpu_maps_update_begin();
+       for (i = 0; i < nthreads; i++) {
+               thread = be32_to_cpu(intserv[i]);
+               for_each_present_cpu(cpu) {
+                       if (get_hard_smp_processor_id(cpu) != thread)
+                               continue;
+
+                       if (get_cpu_current_state(cpu) == CPU_STATE_OFFLINE)
+                               break;
+
+                       if (get_cpu_current_state(cpu) == CPU_STATE_ONLINE) {
+                               set_preferred_offline_state(cpu,
+                                                           CPU_STATE_OFFLINE);
+                               cpu_maps_update_done();
+                               timed_topology_update(1);
+                               rc = device_offline(get_cpu_device(cpu));
+                               if (rc)
+                                       goto out;
+                               cpu_maps_update_begin();
+                               break;
+                       }
+
+                       /*
+                        * The cpu is in CPU_STATE_INACTIVE.
+                        * Upgrade it's state to CPU_STATE_OFFLINE.
+                        */
+                       set_preferred_offline_state(cpu, CPU_STATE_OFFLINE);
+                       WARN_ON(plpar_hcall_norets(H_PROD, thread) != H_SUCCESS);
+                       __cpu_die(cpu);
+                       break;
+               }
+               if (cpu == num_possible_cpus()) {
+                       pr_warn("Could not find cpu to offline with physical id 0x%x\n",
+                               thread);
+               }
+       }
+       cpu_maps_update_done();
+
+out:
+       return rc;
+}
+
 static int dlpar_online_cpu(struct device_node *dn)
 {
        int rc = 0;
@@ -364,8 +420,10 @@ static int dlpar_online_cpu(struct device_node *dn)
                        timed_topology_update(1);
                        find_and_online_cpu_nid(cpu);
                        rc = device_online(get_cpu_device(cpu));
-                       if (rc)
+                       if (rc) {
+                               dlpar_offline_cpu(dn);
                                goto out;
+                       }
                        cpu_maps_update_begin();
 
                        break;
@@ -505,62 +563,6 @@ static ssize_t dlpar_cpu_add(u32 drc_index)
        return rc;
 }
 
-static int dlpar_offline_cpu(struct device_node *dn)
-{
-       int rc = 0;
-       unsigned int cpu;
-       int len, nthreads, i;
-       const __be32 *intserv;
-       u32 thread;
-
-       intserv = of_get_property(dn, "ibm,ppc-interrupt-server#s", &len);
-       if (!intserv)
-               return -EINVAL;
-
-       nthreads = len / sizeof(u32);
-
-       cpu_maps_update_begin();
-       for (i = 0; i < nthreads; i++) {
-               thread = be32_to_cpu(intserv[i]);
-               for_each_present_cpu(cpu) {
-                       if (get_hard_smp_processor_id(cpu) != thread)
-                               continue;
-
-                       if (get_cpu_current_state(cpu) == CPU_STATE_OFFLINE)
-                               break;
-
-                       if (get_cpu_current_state(cpu) == CPU_STATE_ONLINE) {
-                               set_preferred_offline_state(cpu,
-                                                           CPU_STATE_OFFLINE);
-                               cpu_maps_update_done();
-                               timed_topology_update(1);
-                               rc = device_offline(get_cpu_device(cpu));
-                               if (rc)
-                                       goto out;
-                               cpu_maps_update_begin();
-                               break;
-                       }
-
-                       /*
-                        * The cpu is in CPU_STATE_INACTIVE.
-                        * Upgrade it's state to CPU_STATE_OFFLINE.
-                        */
-                       set_preferred_offline_state(cpu, CPU_STATE_OFFLINE);
-                       WARN_ON(plpar_hcall_norets(H_PROD, thread) != H_SUCCESS);
-                       __cpu_die(cpu);
-                       break;
-               }
-               if (cpu == num_possible_cpus()) {
-                       pr_warn("Could not find cpu to offline with physical id 0x%x\n",
-                               thread);
-               }
-       }
-       cpu_maps_update_done();
-
-out:
-       return rc;
-}
-
 static ssize_t dlpar_cpu_remove(struct device_node *dn, u32 drc_index)
 {
        int rc;