Messages in this thread | | | Subject | Re: [PATCH v2 3/5] ALSA: xen-front: Implement Xen event channel handling | From | Oleksandr Andrushchenko <> | Date | Tue, 24 Apr 2018 17:29:15 +0300 |
| |
On 04/24/2018 05:20 PM, Takashi Iwai wrote: > On Mon, 16 Apr 2018 08:24:51 +0200, > Oleksandr Andrushchenko wrote: >> +static irqreturn_t evtchnl_interrupt_req(int irq, void *dev_id) >> +{ >> + struct xen_snd_front_evtchnl *channel = dev_id; >> + struct xen_snd_front_info *front_info = channel->front_info; >> + struct xensnd_resp *resp; >> + RING_IDX i, rp; >> + unsigned long flags; >> + >> + if (unlikely(channel->state != EVTCHNL_STATE_CONNECTED)) >> + return IRQ_HANDLED; >> + >> + spin_lock_irqsave(&front_info->io_lock, flags); >> + >> +again: >> + rp = channel->u.req.ring.sring->rsp_prod; >> + /* ensure we see queued responses up to rp */ >> + rmb(); >> + >> + for (i = channel->u.req.ring.rsp_cons; i != rp; i++) { > I'm not familiar with Xen stuff in general, but through a quick > glance, this kind of code worries me a bit. > > If channel->u.req.ring.rsp_cons has a bogus number, this may lead to a > very long loop, no? Better to have a sanity check of the ring buffer > size. In this loop I have: resp = RING_GET_RESPONSE(&channel->u.req.ring, i); and the RING_GET_RESPONSE macro is designed in the way that it wraps around when *i* in the question gets bigger than the ring size:
#define RING_GET_REQUEST(_r, _idx) \ (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req))
So, even if the counter has a bogus number it will not last long
>> +static irqreturn_t evtchnl_interrupt_evt(int irq, void *dev_id) >> +{ >> + struct xen_snd_front_evtchnl *channel = dev_id; >> + struct xen_snd_front_info *front_info = channel->front_info; >> + struct xensnd_event_page *page = channel->u.evt.page; >> + u32 cons, prod; >> + unsigned long flags; >> + >> + if (unlikely(channel->state != EVTCHNL_STATE_CONNECTED)) >> + return IRQ_HANDLED; >> + >> + spin_lock_irqsave(&front_info->io_lock, flags); >> + >> + prod = page->in_prod; >> + /* ensure we see ring contents up to prod */ >> + virt_rmb(); >> + if (prod == page->in_cons) >> + goto out; >> + >> + for (cons = page->in_cons; cons != prod; cons++) { > Ditto. Same as above > > thanks, > > Takashi Thank you, Oleksandr
| |