[lustre-devel] Regression with delayed_work in sec_gc

[Sebastien Buisson]

> Le 16 mai 2018 à 00:22, NeilBrown <neilb at suse.com> a écrit :
> 
> On Tue, May 15 2018, James Simmons wrote:
> 
>> Dmitry has backported your upstream commit
>> 
>> be3c64da248b1ada2bbcfc3855f07536d8087acb ( ptlrpc: use workqueue for
>> pinger)
>> 
>> and Sebastien tried out the change which can be seen at
>> https://review.whamcloud.com/#/c/31724. Sebastien is having issues with
>> unloading osc, mdc, ost or mdt kernel modules. He writes that he activated
>> Kerberos for my file system, did some IOs, then tried to unmount the
>> client and the  targets. Unfortunately, on some occasions, while
>> unmounting, the mdc module for instance has extra references (as shown by
>> 'lsmod'), and cannot be unloaded. After a while, the extra references are
>> dropped, and the  module can be unloaded. It also happens on occasions on
>> server side, for the mdt or ost modules. I tried destroy_workqueue but
>> that made things worst :-( Do you know what is going on?
> 
> My guess is that ptlrpc_pinger_main() is looping, so
> cancel_delayed_work_sync() is waiting an unusually long time for it.
> This patch might fix the problem - it certainly makes the usage
> of "this_ping" closer to the original code.
> 
> Thanks,
> NeilBrown
> 
> diff --git a/drivers/staging/lustre/lustre/ptlrpc/pinger.c b/drivers/staging/lustre/lustre/ptlrpc/pinger.c
> index 89eef8ec7df4..131b201541e8 100644
> --- a/drivers/staging/lustre/lustre/ptlrpc/pinger.c
> +++ b/drivers/staging/lustre/lustre/ptlrpc/pinger.c
> @@ -222,12 +222,13 @@ static DECLARE_DELAYED_WORK(ping_work, ptlrpc_pinger_main);
> 
> static void ptlrpc_pinger_main(struct work_struct *ws)
> {
> -	unsigned long this_ping = jiffies;
> 	long time_to_next_wake;
> 	struct timeout_item *item;
> 	struct obd_import *imp;
> 
> 	do {
> +		unsigned long this_ping = jiffies;
> +
> 		mutex_lock(&pinger_mutex);
> 		list_for_each_entry(item, &timeout_list, ti_chain) {
> 			item->ti_cb(item, item->ti_cb_data);

Still same problem when testing "ptlrpc: use delayed_work in sec_gc" with patch "ptlrpc: use workqueue for pinger" and modification as suggested above. Kernel module ptlrpc_gss holds extra references, and cannot be unloaded.

However, patch "ptlrpc: use workqueue for pinger" alone does not have the issue.
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