Date: Thu, 17 Sep 2015 09:41:22 +0200 From: Hans Petter Selasky <hps@selasky.org> To: Adrian Chadd <adrian@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r287892 - head/sys/dev/usb/wlan Message-ID: <55FA6EA2.8050809@selasky.org> In-Reply-To: <55FA6C62.6010705@selasky.org> References: <201509170301.t8H31KdP042687@repo.freebsd.org> <55FA6C62.6010705@selasky.org>
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On 09/17/15 09:31, Hans Petter Selasky wrote: > On 09/17/15 05:01, Adrian Chadd wrote: >> Author: adrian >> Date: Thu Sep 17 03:01:19 2015 >> New Revision: 287892 >> URL: https://svnweb.freebsd.org/changeset/base/287892 >> >> Log: >> Use DELAY() rather than usb_pause_mtx() - the latter releases the lock >> before waiting, which prevents the lock from really acting like >> a hardware serialiser. Sigh. >> >> Modified: >> head/sys/dev/usb/wlan/if_rsu.c >> > > This cause a lot more CPU to be burnt. Is there no other way to fix > this? Using an SX lock? > > --HPS > This will not help anything, because at every control request the same lock is dropped again. You need to add an SX lock there, and should revert this pause->DELAY change :-( --HPS
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