Hi Can,
On Fri, 2020-07-31 at 16:58 +0800, Can Guo wrote:
Hi Stanley,
On 2020-07-31 16:22, Stanley Chu wrote:
quoted
Hi Can,
On Mon, 2020-07-27 at 15:30 +0800, Can Guo wrote:
quoted
Hi Stanley,
On 2020-07-24 22:01, Stanley Chu wrote:
quoted
Currently I/O request could be still submitted to UFS device while
UFS is working on shutdown flow. This may lead to racing as below
scenarios and finally system may crash due to unclocked register
accesses.
To fix this kind of issues, specifically quiesce all SCSI devices
before UFS shutdown to block all I/O request sending from block
layer.
Example of racing scenario: While UFS device is runtime-suspended
Thread #1: Executing UFS shutdown flow, e.g.,
ufshcd_suspend(UFS_SHUTDOWN_PM)
Thread #2: Executing runtime resume flow triggered by I/O request,
e.g., ufshcd_resume(UFS_RUNTIME_PM)
I don't quite get it, how can you prevent block layer PM from iniating
hba runtime resume by quiescing the scsi devices? Block layer PM
iniates hba async runtime resume in blk_queue_enter(). But quiescing
the scsi devices can only prevent general I/O requests from passing
through scsi_queue_rq() callback.
Say hba is runtime suspended, if an I/O request to sda is sent from
block layer (sda must be runtime suspended as well at this time),
blk_queue_enter() initiates async runtime resume for sda. But since
sda's parents are also runtime suspended, the RPM framework shall do
runtime resume to the devices in the sequence hba->host->target->sda.
In this case, ufshcd_resume() still runs concurrently, no?
You are right. This patch can not fix the case you mentioned. It just
prevents "general I/O requests".
So perhaps we also need below patch?
#2 scsi: ufs: Use pm_runtime_get_sync in shutdown flow
https://patchwork.kernel.org/patch/10964097/
That is what I am talking about, we definitely need this. Since
you are already working on the fixes to the shutdown path, I will
not upload my fixes (basically look same with yours). However, as
regard for the new change, if pm_runtime_get_sync(hba->dev) < 0,
hba can still be runtime ACTIVE, why directly goto out without a
check of hba's runtime status?
Thanks for reminding this. Then I will fix it and resend both patches as
a new series to fix the shutdown path.
Thanks so much,
Stanley Chu
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