Messages in this thread | | | Date | Wed, 27 Apr 2022 17:45:48 -0700 | From | Jakub Kicinski <> | Subject | Re: [PATCH net v4] nfc: nfcmrvl: main: reorder destructive operations in nfcmrvl_nci_unregister_dev to avoid bugs |
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On Wed, 27 Apr 2022 09:14:38 +0800 Duoming Zhou wrote: > diff --git a/net/nfc/core.c b/net/nfc/core.c > index dc7a2404efd..1d91334ee86 100644 > --- a/net/nfc/core.c > +++ b/net/nfc/core.c > @@ -25,6 +25,8 @@ > #define NFC_CHECK_PRES_FREQ_MS 2000 > > int nfc_devlist_generation; > +/* nfc_download: used to judge whether nfc firmware download could start */ > +static bool nfc_download; > DEFINE_MUTEX(nfc_devlist_mutex); > > /* NFC device ID bitmap */ > @@ -38,7 +40,7 @@ int nfc_fw_download(struct nfc_dev *dev, const char *firmware_name) > > device_lock(&dev->dev); > > - if (!device_is_registered(&dev->dev)) { > + if (!device_is_registered(&dev->dev) || !nfc_download) { > rc = -ENODEV; > goto error; > } > @@ -1134,6 +1136,7 @@ int nfc_register_device(struct nfc_dev *dev) > dev->rfkill = NULL; > } > } > + nfc_download = true; > device_unlock(&dev->dev); > > rc = nfc_genl_device_added(dev); > @@ -1166,6 +1169,7 @@ void nfc_unregister_device(struct nfc_dev *dev) > rfkill_unregister(dev->rfkill); > rfkill_destroy(dev->rfkill); > } > + nfc_download = false; > device_unlock(&dev->dev); > > if (dev->ops->check_presence) {
You can't use a single global variable, there can be many devices each with their own lock.
Paolo suggested adding a lock, if spin lock doesn't fit the bill why not add a mutex?
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