Date: Sat, 22 Dec 2018 15:15:46 +0000 (UTC) From: Vincenzo Maffione <vmaffione@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r342368 - head/sys/dev/netmap Message-ID: <201812221515.wBMFFknS006898@repo.freebsd.org>
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Author: vmaffione Date: Sat Dec 22 15:15:45 2018 New Revision: 342368 URL: https://svnweb.freebsd.org/changeset/base/342368 Log: netmap: fix bug in netmap_poll() optimization The bug was introduced by r339639, although it is present in the upstream netmap code since 2015. It is due to resetting the want_rx variable to POLLIN, rather than resetting it to POLLIN|POLLRDNORM. It only affects select(), which uses POLLRDNORM. poll() is not affected, because it uses POLLIN. Also, it only affects FreeBSD, because Linux skips the optimization implemented by the piece of code where the bug occurs. MFC after: 3 days Sponsored by: Sunny Valley Networks Modified: head/sys/dev/netmap/netmap.c Modified: head/sys/dev/netmap/netmap.c ============================================================================== --- head/sys/dev/netmap/netmap.c Sat Dec 22 11:38:54 2018 (r342367) +++ head/sys/dev/netmap/netmap.c Sat Dec 22 15:15:45 2018 (r342368) @@ -3304,16 +3304,19 @@ netmap_poll(struct netmap_priv_d *priv, int events, NM } if (want_rx) { enum txrx t = NR_RX; - want_rx = 0; /* look for a reason to run the handlers */ + int rxsync_needed = 0; + + /* look for a reason to run the handlers */ for (i = priv->np_qfirst[t]; i < priv->np_qlast[t]; i++) { kring = NMR(na, t)[i]; if (kring->ring->cur == kring->ring->tail /* try fetch new buffers */ || kring->rhead != kring->ring->head /* release buffers */) { - want_rx = 1; + rxsync_needed = 1; + break; } } - if (!want_rx) - revents |= events & (POLLIN | POLLRDNORM); /* we have data */ + if (!rxsync_needed) + revents |= want_rx; /* we have data */ } #endif
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