From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6C27BC433E7 for ; Tue, 13 Oct 2020 11:10:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 266D221548 for ; Tue, 13 Oct 2020 11:10:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602587420; bh=QM+nvI722PuUaCbJjwtF4VtruSHvxnlMXoRt5pyjiIc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=NC44zwtiSg/HE9ngRmxDsbp+fk+KpI66eYf5sxNIJC6IP9DOq9gG+ZRSZ72Ydz1BK gQLJDC7qj8g6qy6XruLTq0GFeqG/S/PTbusj/oO0RfQtUlQ15QPSdD95opB1Z5Idlr eNaJDH0ZXlPL9drqYVZ+CUvKTxGy9+d1ZrjHa218= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731195AbgJMLKT (ORCPT ); Tue, 13 Oct 2020 07:10:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:44194 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726662AbgJMLKS (ORCPT ); Tue, 13 Oct 2020 07:10:18 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 49EFF214DB; Tue, 13 Oct 2020 11:10:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602587417; bh=QM+nvI722PuUaCbJjwtF4VtruSHvxnlMXoRt5pyjiIc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=MNCTYpBtgN5rwgqV64fESdMTkMO3SXBldohkqvVSaMG+SE8H51511hmPidRonjKPm fyddFGNix2Qos55yYTQk2CCxEK4Mhr0PhkTTwC8RDuoEyiypTd4PnE/mOkeuCbEOds CKLU+0NkQ1qH+6fTM8OovISWzIofHRg6jpiW9u4E= Date: Tue, 13 Oct 2020 13:10:55 +0200 From: Greg KH To: Pratham Pratap Cc: stern@rowland.harvard.edu, rafael.j.wysocki@intel.com, mathias.nyman@linux.intel.com, andriy.shevchenko@linux.intel.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, sallenki@codeaurora.org, mgautam@codeaurora.org, jackp@codeaurora.org, stable@vger.kernel.org Subject: Re: [PATCH] usb: core: Don't wait for completion of urbs Message-ID: <20201013111055.GA1942304@kroah.com> References: <1602586022-13239-1-git-send-email-prathampratap@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1602586022-13239-1-git-send-email-prathampratap@codeaurora.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 13, 2020 at 04:17:02PM +0530, Pratham Pratap wrote: > Consider a case where host is trying to submit urbs to the > connected device while holding the us->dev_mutex and due to > some reason it is stuck while waiting for the completion of > the urbs. Now the scsi error mechanism kicks in and it calls > the device reset handler which is trying to acquire the same > mutex causing a deadlock situation. > > Below is the call stack of the task which acquired the mutex > (0xFFFFFFC660447460) and waiting for completion. > > B::v.f_/task_0xFFFFFFC6604DB280 > -000|__switch_to(prev = 0xFFFFFFC6604DB280, ?) > -001|prepare_lock_switch(inline) > -001|context_switch(inline) > -001|__schedule(?) > -002|schedule() > -003|schedule_timeout(timeout = 9223372036854775807) > -004|do_wait_for_common(x = 0xFFFFFFC660447570, > action = 0xFFFFFF98ED5A7398, timeout = 9223372036854775807, ?) > -005|spin_unlock_irq(inline) > -005|__wait_for_common(inline) > -005|wait_for_common(inline) > -005|wait_for_completion(x = 0xFFFFFFC660447570) > -006|sg_clean(inline) > -006|usb_sg_wait() > -007|atomic64_andnot(inline) > -007|atomic_long_andnot(inline) > -007|clear_bit(inline) > -007|usb_stor_bulk_transfer_sglist(us = 0xFFFFFFC660447460, > pipe = 3221291648, sg = 0xFFFFFFC65D6415D0, ?, length = 512, > act_len = 0xFFFFFF801258BC90) No need to line-wrap for stuff like this. > -008|scsi_bufflen(inline) > -008|usb_stor_bulk_srb(inline) > -008|usb_stor_Bulk_transport(srb = 0xFFFFFFC65D641438, > us = 0xFFFFFFC660447460) > -009|test_bit(inline) > -009|usb_stor_invoke_transport(srb = 0xFFFFFFC65D641438, > us = 0xFFFFFFC660447460) > -010|usb_stor_transparent_scsi_command(?, ?) > -011|usb_stor_control_thread(__us = 0xFFFFFFC660447460) //us->dev_mutex > -012|kthread(_create = 0xFFFFFFC6604C5E80) > -013|ret_from_fork(asm) > ---|end of frame > > Below is the call stack of the task which trying to acquire the same > mutex(0xFFFFFFC660447460) in the error handling path. > > B::v.f_/task_0xFFFFFFC6609AA1C0 > -000|__switch_to(prev = 0xFFFFFFC6609AA1C0, ?) > -001|prepare_lock_switch(inline) > -001|context_switch(inline) > -001|__schedule(?) > -002|schedule() > -003|schedule_preempt_disabled() > -004|__mutex_lock_common(lock = 0xFFFFFFC660447460, state = 2, ?, ?, ?, > ?, ?) > -005|__mutex_lock_slowpath(?) > -006|__cmpxchg_acq(inline) > -006|__mutex_trylock_fast(inline) > -006|mutex_lock(lock = 0xFFFFFFC660447460) //us->dev_mutex > -007|device_reset(?) > -008|scsi_try_bus_device_reset(inline) > -008|scsi_eh_bus_device_reset(inline) > -008|scsi_eh_ready_devs(shost = 0xFFFFFFC660446C80, > work_q = 0xFFFFFF80191C3DE8, done_q = 0xFFFFFF80191C3DD8) > -009|scsi_error_handler(data = 0xFFFFFFC660446C80) > -010|kthread(_create = 0xFFFFFFC66042C080) > -011|ret_from_fork(asm) > ---|end of frame > > Fix this by adding 5 seconds timeout while waiting for completion. > > Fixes: 3e35bf39e (USB: fix codingstyle issues in drivers/usb/core/message.c) Please read the documentation for how to properly add a Fixes: line (hint, your sha1 isn't big enough.) And does this really "fix" a commit that chnaged the coding style? I doubt that... > Cc: stable@vger.kernel.org > Signed-off-by: Pratham Pratap > --- > drivers/usb/core/message.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c > index ae1de9c..b1e839c 100644 > --- a/drivers/usb/core/message.c > +++ b/drivers/usb/core/message.c > @@ -515,15 +515,13 @@ EXPORT_SYMBOL_GPL(usb_sg_init); > */ > void usb_sg_wait(struct usb_sg_request *io) > { > - int i; > + int i, retval; > int entries = io->entries; > > /* queue the urbs. */ > spin_lock_irq(&io->lock); > i = 0; > while (i < entries && !io->status) { > - int retval; > - > io->urbs[i]->dev = io->dev; > spin_unlock_irq(&io->lock); > > @@ -569,7 +567,13 @@ void usb_sg_wait(struct usb_sg_request *io) > * So could the submit loop above ... but it's easier to > * solve neither problem than to solve both! > */ > - wait_for_completion(&io->complete); > + retval = wait_for_completion_timeout(&io->complete, > + msecs_to_jiffies(5000)); Where did you pick 5 seconds from? Are you sure that will work properly? What about devices with very long i/o stalls when data is being flushed out, are you sure this will not trigger there? > + if (retval == 0) { > + dev_err(&io->dev->dev, "%s, timed out while waiting for io_complete\n", > + __func__); > + usb_sg_cancel(io); So this is cancelled, but how does userspace know the error happened and it was a timeout? thanks, greg k-h