Re: [PATCH] soc: qcom: pdr: Fix the potential deadlock

[Dmitry Baryshkov]

On Tue, Jan 28, 2025 at 01:37:51PM +0530, Mukesh Ojha wrote:
> When some client process A call pdr_add_lookup() to add the look up for
> the service and does schedule locator work, later a process B got a new
> server packet indicating locator is up and call pdr_locator_new_server()
> which eventually sets pdr->locator_init_complete to true which process A
> sees and takes list lock and queries domain list but it will timeout due
> to deadlock as the response will queued to the same qmi->wq and it is
> ordered workqueue and process B is not able to complete new server
> request work due to deadlock on list lock.
> 
>        Process A                        Process B
> 
>                                      process_scheduled_works()
> pdr_add_lookup()                      qmi_data_ready_work()
>  process_scheduled_works()             pdr_locator_new_server()
>                                          pdr->locator_init_complete=true;
>    pdr_locator_work()
>     mutex_lock(&pdr->list_lock);
> 
>      pdr_locate_service()                  mutex_lock(&pdr->list_lock);
> 
>       pdr_get_domain_list()
>        pr_err("PDR: %s get domain list
>                txn wait failed: %d\n",
>                req->service_name,
>                ret);
> 
> Fix it by removing the unnecessary list iteration as the list iteration
> is already being done inside locator work, so avoid it here and just
> call schedule_work() here.
> 
> Signed-off-by: Saranya R <quic_sarar@xxxxxxxxxxx>
> Signed-off-by: Mukesh Ojha <mukesh.ojha@xxxxxxxxxxxxxxxx>

Missing Fixes tag.

> ---
>  drivers/soc/qcom/pdr_interface.c | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
> 

-- 
With best wishes
Dmitry