Hi, On Wed, Oct 05, 2016 at 02:04:53PM +0000, Amitkumar Karwar wrote: > > From: Brian Norris [mailto:briannorris@xxxxxxxxxxxx] > > Sent: Wednesday, October 05, 2016 3:28 AM > > To: Amitkumar Karwar > > Cc: linux-wireless@xxxxxxxxxxxxxxx; Cathy Luo; Nishant Sarmukadam; > > rajatja@xxxxxxxxxx; briannorris@xxxxxxxxxx; Xinming Hu > > Subject: Re: [PATCH v2 1/2] mwifiex: reset card->adapter during device > > unregister > > > > Hi, > > > > On Tue, Oct 04, 2016 at 10:38:24PM +0530, Amitkumar Karwar wrote: > > > --- a/drivers/net/wireless/marvell/mwifiex/pcie.c > > > +++ b/drivers/net/wireless/marvell/mwifiex/pcie.c > > > @@ -3042,6 +3042,7 @@ static void mwifiex_unregister_dev(struct > > mwifiex_adapter *adapter) > > > pci_disable_msi(pdev); > > > } > > > } > > > + card->adapter = NULL; > > > > I think you have a similar problem here as in patch 2; there is no > > locking to protect fields in struct pcie_service_card or struct > > sdio_mmc_card below. That problem kind of already exists, except that > > you only write the value of card->adapter once at registration time, so > > it's not actually unsafe. But now that you're introducing a second > > write, you have a problem. > > > > Brian > > > > We have a global "add_remove_card_sem" semaphore in our code for > synchronizing initialization and teardown threads. Ideally "init + > teardown/reboot" should not have a race issue with this logic > > Later there was a loophole introduced in this after using async > firmware download API. During initialization, firmware downloads > asynchronously in a separate thread where might have released the > semaphore. I am working on a patch to fix this. > > So "card->adapter" doesn't need to have locking. Even if we have two > write operations, those two threads can't run simultaneously due to > above mentioned logic. What about writes racing with reads? You have lots of unsynchronized cases that read this, although most of them should be halted by now (e.g., cmd processing). I was looking at suspend() in particular, which I thought you were looking at in this patch series. Brian
