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Fixup a hang while performing a read operation on XenStore

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Reyk has reported an issue that turned out to be an incorrect calculation
of bytes available for reading.  This diff also places missed semaphore
releases in the xs_start and makes 'left' a size_t in xs_ring_{get,put}.
This commit is contained in:
mikeb 2016-01-18 18:54:38 +00:00
parent d28efb3f5e
commit 09cf2d6e77
1 changed files with 7 additions and 4 deletions
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11
sys/dev/pv/xenstore.c
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@ -1,4 +1,4 @@
/* $OpenBSD: xenstore.c,v 1.18 2016/01/15 18:20:41 mikeb Exp $ */
/* $OpenBSD: xenstore.c,v 1.19 2016/01/18 18:54:38 mikeb Exp $ */
/*
* Copyright (c) 2015 Mike Belopuhov
@ -311,7 +311,8 @@ xs_ring_avail(struct xs_ring *xsr, int req)
uint32_t prod = req ? xsr->xsr_req_prod : xsr->xsr_rsp_prod;
membar_consumer();
return ((cons - prod - 1) & (XS_RING_SIZE - 1));
KASSERT(prod - cons <= XS_RING_SIZE);
return (req ? XS_RING_SIZE - (prod - cons) : prod - cons);
}
int
@ -373,6 +374,7 @@ xs_start(struct xs_transaction *xst, struct xs_msg *xsm, struct iovec *iov,
if (xs_output(xst, (uint8_t *)&xsm->xsm_hdr,
sizeof(xsm->xsm_hdr)) == -1) {
printf("%s: failed to write the header\n", __func__);
xs_sem_put(&xs->xs_rngsem);
return (-1);
}
@ -381,6 +383,7 @@ xs_start(struct xs_transaction *xst, struct xs_msg *xsm, struct iovec *iov,
if (xs_output(xst, iov[i].iov_base, iov[i].iov_len) == -1) {
printf("%s: failed on iovec #%d len %ld\n", __func__,
i, iov[i].iov_len);
xs_sem_put(&xs->xs_rngsem);
return (-1);
}
}
@ -435,7 +438,7 @@ xs_ring_put(struct xs_softc *xs, void *src, size_t size)
struct xs_ring *xsr = xs->xs_ring;
uint32_t prod = xsr->xsr_req_prod & (XS_RING_SIZE - 1);
uint32_t avail = xs_ring_avail(xsr, 1);
int left;
size_t left;
membar_consumer();
if (size > XS_RING_SIZE)
@ -463,7 +466,7 @@ xs_ring_get(struct xs_softc *xs, void *dst, size_t size)
struct xs_ring *xsr = xs->xs_ring;
uint32_t cons = xsr->xsr_rsp_cons & (XS_RING_SIZE - 1);
uint32_t avail = xs_ring_avail(xsr, 0);
int left;
size_t left;
membar_consumer();
if (size > XS_RING_SIZE)