Return-path: Received: from wolverine02.qualcomm.com ([199.106.114.251]:45843 "EHLO wolverine02.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750980AbcIIMQ0 (ORCPT ); Fri, 9 Sep 2016 08:16:26 -0400 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Subject: Re: [1/2] carl9170: Fix wrong completion usage From: Kalle Valo In-Reply-To: <1471525926-20384-2-git-send-email-wagi@monom.org> To: Daniel Wagner CC: Kalle Valo , Christian Lamparter , "Luis R . Rodriguez" , , , , , Daniel Wagner Message-ID: (sfid-20160909_141649_116252_6603D96C) Date: Fri, 9 Sep 2016 14:16:17 +0200 Sender: linux-wireless-owner@vger.kernel.org List-ID: Daniel Wagner wrote: > From: Daniel Wagner > > carl9170_usb_stop() is used from several places to flush and cleanup any > pending work. The normal pattern is to send a request and wait for the > irq handler to call complete(). The completion is not reinitialized > during normal operation and as the old comment indicates it is important > to keep calls to wait_for_completion_timeout() and complete() balanced. > > Calling complete_all() brings this equilibirum out of balance and needs > to be fixed by a reinit_completion(). But that opens a small race > window. It is possible that the sequence of complete_all(), > reinit_completion() is faster than the wait_for_completion_timeout() can > do its work. The wake up is not lost but the done counter test is after > reinit_completion() has been executed. The only reason we don't see > carl9170_exec_cmd() hang forever is we use the timeout version of > wait_for_copletion(). > > Let's fix this by reinitializing the completion (that is just setting > done counter to 0) just before we send out an request. Now, > carl9170_usb_stop() can be sure a complete() call is enough to make > progess since there is only one waiter at max. This is a common pattern > also seen in various drivers which use completion. > > Signed-off-by: Daniel Wagner Thanks, 1 patch applied to ath-next branch of ath.git: 78a9e170388b carl9170: Fix wrong completion usage -- Sent by pwcli https://patchwork.kernel.org/patch/9287819/