Hi, I have read the manual page of bus_dmamap_load_mbuf_sg. This call will always return immediately and will not block for any reason. Sorry for my wrong report, please ignore it.
Thanks, Jia-Ju Bai On 2017/6/18 9:04, Jia-Ju Bai wrote:
The alc driver may sleep under a mutex, and the function call paths in file "sys/dev/alc/if_alc.c" are: alc_resume [acquire the mutex] alc_init_locked alc_init_rx_ring alc_newbuf bus_dmamap_load_mbuf_sg(BUS_DMA_WAITOK) --> may sleep alc_start [acquire the mutex] alc_start_locked alc_encap bus_dmamap_load_mbuf_sg(BUS_DMA_WAITOK) --> may sleep The possible fix of these bugs is to set the last parameter in bus_dmamap_load_mbuf_sg to "BUS_DMA_NOWAIT". This bug is found by a static analysis tool written by myself, and it is checked by my review of the FreeBSD code. Signed-off-by: Jia-Ju Bai <[email protected]> --- sys/dev/alc/if_alc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/sys/dev/alc/if_alc.c b/sys/dev/alc/if_alc.c index ca7ae9d17b5..cb0f15e223b 100644 --- a/sys/dev/alc/if_alc.c +++ b/sys/dev/alc/if_alc.c @@ -2795,7 +2795,7 @@ alc_encap(struct alc_softc *sc, struct mbuf **m_head) map = txd->tx_dmamap;error = bus_dmamap_load_mbuf_sg(sc->alc_cdata.alc_tx_tag, map,- *m_head, txsegs, &nsegs, 0); + *m_head, txsegs, &nsegs, BUS_DMA_NOWAIT); if (error == EFBIG) { m = m_collapse(*m_head, M_NOWAIT, ALC_MAXTXSEGS); if (m == NULL) { @@ -2805,7 +2805,7 @@ alc_encap(struct alc_softc *sc, struct mbuf **m_head) } *m_head = m; error = bus_dmamap_load_mbuf_sg(sc->alc_cdata.alc_tx_tag, map, - *m_head, txsegs, &nsegs, 0); + *m_head, txsegs, &nsegs, BUS_DMA_NOWAIT); if (error != 0) { m_freem(*m_head); *m_head = NULL; @@ -3487,7 +3487,7 @@ alc_newbuf(struct alc_softc *sc, struct alc_rxdesc *rxd) #endifif (bus_dmamap_load_mbuf_sg(sc->alc_cdata.alc_rx_tag,- sc->alc_cdata.alc_rx_sparemap, m, segs, &nsegs, 0) != 0) { + sc->alc_cdata.alc_rx_sparemap, m, segs, &nsegs, BUS_DMA_NOWAIT) != 0) { m_freem(m); return (ENOBUFS); }
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