From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lamorak.hansenpartnership.com (lamorak.hansenpartnership.com [198.37.111.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 90CF33A1E72; Sat, 3 Jan 2026 19:55:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.37.111.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767470159; cv=none; b=pF5qaL4S3ENdV+d5CsT2Q8RgZPCyUq2akEEeWzi8DAcirMGFMAEkMmX5r+xPwsYh+3DiJ7R4YIkvpUlFparUoycLvadiRqTeLoVhiKQZ7q7+kU7ZBOTQjZBZel+iQsa//xXm4rlEnF8EmnU9mw0Xcgk4hKeVj1v/c42D7Y++PzA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767470159; c=relaxed/simple; bh=TFW0RmhbZ0h4ZWCC5NuC0HE/UfE7fbfvqa2FrwJUeG4=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; 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 8mT2Eh9SkH+YVOmaKsajgZgrBxA7fWmGoxXswEVxJIFj3vW7yNc0C5HaUdYa5iGOMs4kg2ht4s7yy7NRQuh7BifWjo6BQ6k4S1H+6axZucxhSV1L6zN9d+lr3Xo/vy1unzA== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 Precedence: bulk X-Mailing-List: linux-scsi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Sat, 2026-01-03 at 10:24 +0800, duoming@zju.edu.cn wrote: > On Thu, 01 Jan 2026 10:21:28 -0500, James Bottomley wrote: > > > diff --git a/drivers/scsi/ppa.c b/drivers/scsi/ppa.c > > > index ea682f3044b..8da2a78ebac 100644 > > > --- a/drivers/scsi/ppa.c > > > +++ b/drivers/scsi/ppa.c > > > @@ -1136,6 +1136,7 @@ static void ppa_detach(struct parport *pb) > > > =C2=A0 ppa_struct *dev; > > > =C2=A0 list_for_each_entry(dev, &ppa_hosts, list) { > > > =C2=A0 if (dev->dev->port =3D=3D pb) { > > > + disable_delayed_work_sync(&dev->ppa_tq); > > > =C2=A0 list_del_init(&dev->list); > > > =C2=A0 scsi_remove_host(dev->host); > > > =C2=A0 scsi_host_put(dev->host); > >=20 > > This fix looks bogus: if there's an active workqueue on ppa it's > > because there's an outstanding command and it's emulating polling.=C2= =A0 > > If you stop the polling by disabling the workqueue, the command > > will never return and the host will never get freed, so this will > > leak resources, won't it? >=20 > I believe that disabling the ppa_tq delayed work will not affect the > Scsi_Host release process. The lifetime of the Scsi_Host is managed > by tagset_refcnt. The tagset_refcnt is initialized to 1 in > scsi_add_host_with_dma() and decreased to 0 in scsi_remove_host(). > since the delayed work callback ppa_interrupt() does not modify > tagset_refcnt in any way, the host could be freed as expected. Not if something else holds a reference to the host, which an outstanding command does. That's the point I was making above: as long as the command doesn't return, everything is pinned and never gets freed (well, possibly until timeout). You cause that because the work queue is only active if a command is outstanding, so when you disable the queue in that situation the command remains outstanding and can never complete normally. > > Also the race condition you identify is one of many tied to an > > incorrect ppa_struct lifetime: it should never be free'd before the > > host itself is gone because a live host may do a callback which > > will get the ppa_struct from hostdata, so if the host is still > > alive for any reason when ppa_detach() is called, we'll get the > > same problem. >=20 > The ppa_struct is properly freed only after ensuring the complete > removal of the associated Scsi_Host in ppa_detach(). The detailed > sequence is as follows: >=20 > ... > =C2=A0 =C2=A0scsi_remove_host(dev->host); > =C2=A0 =C2=A0scsi_host_put(dev->host); //the host is gone The host is not gone if that put is not the final one as it won't be if there's an outstanding command pinning the device. Regards, James