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Subject[RFC][PATCH] PM: disable nonboot cpus before suspending devices
hi Rafael,

on s390 we have a reproduceable testcase where, after all devices were
suspended, a memory allocation results in disk IO. I know that this is
similar to the current discussion about magically changing the gpf mask,
but in our case the related allocation is triggered not by a device driver
but directly by hibernation_snapshot. The call chain looks like this:

STACK:
0 schedule+1796 [0x5a7af0]
1 io_schedule+98 [0x5a82ce]
2 sync_page_killable+4 [0x1ec424]
3 __wait_on_bit+204 [0x5a8bc4]
4 add_to_page_cache_locked+2 [0x1ec766]
5 shrink_page_list+2372 [0x1fc5b0]
6 shrink_list+2496 [0x1fd02c]
7 shrink_zone+932 [0x1fd3e0]
8 try_to_free_pages+668 [0x1fe4bc]
9 __alloc_pages_nodemask+1346 [0x1f5056]
10 __get_free_pages+76 [0x1f52dc]
11 __build_sched_domains+60 [0x144f98]
12 partition_sched_domains+696 [0x145dcc]
13 update_sched_domains+100 [0x146104]
14 notifier_call_chain+166 [0x5ae112]
15 raw_notifier_call_chain+44 [0x1800c4]
16 _cpu_down+586 [0x59f212]
17 disable_nonboot_cpus+354 [0x155ad2]
18 hibernation_snapshot+324 [0x1a7938]
19 hibernate+304 [0x1a7bcc]
20 state_store+130 [0x1a645e]
21 sysfs_write_file+264 [0x2b551c]
22 vfs_write+190 [0x23f98a]
23 sys_write+100 [0x23fb50]
24 sysc_noemu+16 [0x118ff6]

a possible fix would be to call disable_nonboot_cpus before suspending the
devices..
NOTE: this affects pm debug modes
---

Since disable_nonboot_cpus triggers memory allocations we should call
it before suspending the devices in hibernation_snapshot.

Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
---
kernel/power/hibernate.c | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)

--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -229,13 +229,9 @@ static int create_image(int platform_mod
}

error = platform_pre_snapshot(platform_mode);
- if (error || hibernation_test(TEST_PLATFORM))
- goto Platform_finish;
-
- error = disable_nonboot_cpus();
- if (error || hibernation_test(TEST_CPUS)
+ if (error || hibernation_test(TEST_PLATFORM)
|| hibernation_testmode(HIBERNATION_TEST))
- goto Enable_cpus;
+ goto Platform_finish;

local_irq_disable();

@@ -269,9 +265,6 @@ static int create_image(int platform_mod
Enable_irqs:
local_irq_enable();

- Enable_cpus:
- enable_nonboot_cpus();
-
Platform_finish:
platform_finish(platform_mode);

@@ -303,6 +296,10 @@ int hibernation_snapshot(int platform_mo
if (error)
goto Close;

+ error = disable_nonboot_cpus();
+ if (error || hibernation_test(TEST_CPUS))
+ goto Enable_cpus;
+
suspend_console();
error = dpm_suspend_start(PMSG_FREEZE);
if (error)
@@ -322,6 +319,8 @@ int hibernation_snapshot(int platform_mo
dpm_resume_end(in_suspend ?
(error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE);
resume_console();
+ Enable_cpus:
+ enable_nonboot_cpus();
Close:
platform_end(platform_mode);
return error;

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