On Wed, May 12, 2010 at 7:50 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> On Tue, 11 May 2010, Matt Reimer wrote:
>
>> >> or has a consensus about how to fix this been
>> >> achieved? I'm hitting the same problem and have some time to work on a
>> >> fix.
>> >
>> > Generally, it looks like del_gendisk should thaw writeback threads, but not
>> > during suspend, only during resume.
>>
>> Thawing the writeback thread only during resume does fix the case
>> Maxim originally presented:
>>
>> 0. build kernel with CONFIG_MMC_UNSAFE_RESUME
>> 1. insert SD card
>> 2. suspend
>> 3. remove SD card while suspended
>> 4. resume from suspend hangs
>>
>> But if CONFIG_MMC_UNSAFE_RESUME is not set, the kernel oopses during
>> suspend because the MMC device suspend times out:
>>
>> mmc0: card e624 removed
>> **** DPM device timeout: pxa2xx-mci.0 (pxa2xx-mci)
>> kernel BUG at /home/mreimer/sdg/android/android-2.1/kernel/drivers/base/power/main.c:453!
>> Unable to handle kernel NULL pointer dereference at virtual address 00000000
>> pgd = c0004000
>> [00000000] *pgd=00000000
>> Internal error: Oops: 817 [#1] PREEMPT
>>
>> If I thaw the writeback thread unconditionally in del_gendisk() then
>> suspend and resume work as expected for both CONFIG_MMC_UNSAFE_RESUME
>> set/not set, even when the card is removed while suspended.
>>
>> So what is the proper fix?
>
> I don't see any reason not to let del_gendisk thaw the writeback thread
> during suspend. Since the device is going away anyhow, letting the
> thread run shouldn't cause any problems.
So how does the attached patch look?
Matt
>From 20d8340471eb05aa54af1349f4ddccecd9c230c6 Mon Sep 17 00:00:00 2001
From: Matt Reimer <mreimer@xxxxxxxxxxxxxx>
Date: Thu, 13 May 2010 14:36:54 -0700
Subject: [PATCH] fs: prevent hang on suspend/resume when MMC/SD card present
Devices can come and go from the MMC/SD bus during suspend or resume,
when the writeback thread is frozen, resulting in a hang. So thaw the
writeback thread in del_gendisk() to prevent the hang.
Signed-off-by: Matt Reimer <mreimer@xxxxxxxxxxxxxx>
---
fs/partitions/check.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index e238ab2..b303919 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -666,6 +666,8 @@ void del_gendisk(struct gendisk *disk)
struct disk_part_iter piter;
struct hd_struct *part;
+ thaw_process(disk->queue->backing_dev_info.wb.task);
+
/* invalidate stuff */
disk_part_iter_init(&piter, disk,
DISK_PITER_INCL_EMPTY | DISK_PITER_REVERSE);
--
1.7.0.4
Attachment:
0001-fs-prevent-hang-on-suspend-resume-when-MMC-SD-card-p.patch
Description: Binary data
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