Hi Dmitry, > From: Dmitry Torokhov [mailto:dmitry.torokhov@xxxxxxxxx] > Sent: Tuesday, October 25, 2016 5:28 AM > To: Brian Norris > Cc: Amitkumar Karwar; linux-wireless@xxxxxxxxxxxxxxx; Cathy Luo; Nishant > Sarmukadam > Subject: Re: [PATCH 2/5] mwifiex: use spinlock for 'mwifiex_processing' > in shutdown_drv > > On Mon, Oct 24, 2016 at 12:19:15PM -0700, Brian Norris wrote: > > On Mon, Oct 24, 2016 at 07:51:29PM +0530, Amitkumar Karwar wrote: > > > This variable is guarded by spinlock at all other places. This patch > > > takes care of missing spinlock usage in mwifiex_shutdown_drv(). > > > > > > Signed-off-by: Amitkumar Karwar <akarwar@xxxxxxxxxxx> > > > --- > > > drivers/net/wireless/marvell/mwifiex/init.c | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/drivers/net/wireless/marvell/mwifiex/init.c > > > b/drivers/net/wireless/marvell/mwifiex/init.c > > > index 82839d9..8e5e424 100644 > > > --- a/drivers/net/wireless/marvell/mwifiex/init.c > > > +++ b/drivers/net/wireless/marvell/mwifiex/init.c > > > @@ -670,11 +670,14 @@ mwifiex_shutdown_drv(struct mwifiex_adapter > > > *adapter) > > > > > > adapter->hw_status = MWIFIEX_HW_STATUS_CLOSING; > > > /* wait for mwifiex_process to complete */ > > > + spin_lock_irqsave(&adapter->main_proc_lock, flags); > > > if (adapter->mwifiex_processing) { > > > > I'm not quite sure why we have this check in the first place; if the > > main process is still running, then don't we have bigger problems here > > anyway? But this is definitely the "right" way to check this flag, so: > > No, this is definitely not right way to check it. What exactly does this > spinlock protect? It seems that the intent is to make sure we do not > call mwifiex_shutdown_drv() while mwifiex_main_process() is executing. > It even says above that we are "waiting" for it (but we do not, we may > bail out or we may not, depends on luck). > > To implement this properly you not only need to take a lock and check > the flag, but keep the lock until mwifiex_shutdown_drv() is done, or use > some other way to let mwifiex_main_process() know it should not access > the adapter while mwifiex_shutdown_drv() is running. > > NACK. > As I explained in other email, here is the sequence. 1) We find mwifiex_processing is true in mwifiex_shitdown_drv(). "-EINPROGRESS" is returned by the function and hw_status state is changed to MWIFIEX_HW_STATUS_CLOSING. 2) We wait until main_process is completed. if (mwifiex_shutdown_drv(adapter) == -EINPROGRESS) wait_event_interruptible(adapter->init_wait_q, adapter->init_wait_q_woken); 3) We have following check at the end of main_process() exit_main_proc: if (adapter->hw_status == MWIFIEX_HW_STATUS_CLOSING) mwifiex_shutdown_drv(adapter); 4) Here at the end of mwifiex_shutdown_drv(), we are setting "adapter->init_wait_q_woken" and waking up the thread in point (2) Regards, Amitkumar
