Date: Thu, 27 Feb 2014 16:42:58 +0900 (JST) From: Kohji Okuno <okuno.kohji@jp.panasonic.com> To: hps@bitfrost.no Cc: jmg@funkthat.com, freebsd-current@freebsd.org, okuno.kohji@jp.panasonic.com Subject: Re: kqueue for usb_dev Message-ID: <20140227.164258.18190762432316083.okuno.kohji@jp.panasonic.com> In-Reply-To: <530EEA2A.50604@bitfrost.no> References: <20140227060232.GA47921@funkthat.com> <20140227.161317.453723361596662298.okuno.kohji@jp.panasonic.com> <530EEA2A.50604@bitfrost.no>
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From: Hans Petter Selasky <hps@bitfrost.no> > On 02/27/14 08:13, Kohji Okuno wrote: >> Hi John-Mark, >> >> Thank you for you comment. >> >> From: John-Mark Gurney <jmg@funkthat.com> >>> Kohji Okuno wrote this message on Thu, Feb 27, 2014 at 14:26 +0900: >>>> I tried add kqueue I/F to usb_dev.c. I attached my patch. >>>> What do you think about my patch? >>> >>> A few comments... >>> >>> 1) You should just drop the use of flag_iskevent and just >>> unconditionally call KNOTE... since you have the lock already held, >>> the cost is minimal (and w/ modern branch prediction, may be cheaper)... >> >> Should we set the use of flag_iskevent, when usb_filter_read() and >> usb_filter_write() return `0'? >> >> >>> 2) Why do you try to start read/write transfers in the _filter? You >>> should just check to see if data is available and not do work.. This >>> is also important since kqueue calls the filter just before delivering >>> the knote to userland to verify that there is still data, and it will >>> call your _event function for each knote on the fd... The work should >>> be started through other mechanisms, like read/write syscall or >>> interrupt or timeout/callout... If it's required to get results from >>> USB_IF_POLL, then it's fine.. >> >> I copied from usb_poll(). >> Should we try to start read/write transfers in usb_kqfilter()? >> Or should not we try to start read/write transfers in poll and kqueue? >> >>> 3) I don't see any calls to knlist_destroy... These calls are needed >>> to clean up the knlist... >> >> I understood. >> >>> Obviously the #if 1's will need to go... >>> >>> Also, I don't think your change is against HEAD.. The line numbers >>> in my version of usb_dev.c are different... >> >> I'm sorry. > > > Hi, > > I've found two bugs: > > 1) > > > +#if 1 > + knlist_init_mtx(&f_tx->selinfo.si_note, f_rx->priv_mtx); > +#endif > > Should be: > > +#if 1 > + knlist_init_mtx(&f_tx->selinfo.si_note, f_tx->priv_mtx); > +#endif > > > 2) > > Event filters need to lock the FIFO's mutex. > > BTW: I'm working on getting the code into -HEAD. I'll run some test before it > goes in. Hi, Thank you for you comment. 1) You are right. 2) I think that priv_mtx is hold in caller function. Would you refer to kqueue_scan() in kern/kern_event.c? Thanks, Kohji Okuno
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