linux-kernel - Re: [PATCH] pata_parport: add driver (PARIDE replacement)

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Message-Id: <202211151556.52895.linux@zary.sk>
Date:   Tue, 15 Nov 2022 15:56:52 +0100
From:   Ondrej Zary <linux@...y.sk>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Cc:     Christoph Hellwig <hch@....de>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        Jens Axboe <axboe@...nel.dk>, Tim Waugh <tim@...erelk.net>,
        linux-block@...r.kernel.org, linux-parport@...ts.infradead.org,
        linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pata_parport: add driver (PARIDE replacement)

On Tuesday 15 November 2022, Damien Le Moal wrote:
> On 11/15/22 04:25, Ondrej Zary wrote:
> > On Monday 14 November 2022 09:03:28 Damien Le Moal wrote:
> >> On 11/14/22 16:53, Ondrej Zary wrote:
> >>> On Monday 14 November 2022, Damien Le Moal wrote:
> >>>> On 11/12/22 20:17, Ondrej Zary wrote:
> >>>>> On Wednesday 19 October 2022 09:34:31 Christoph Hellwig wrote:
> >>>>>> It's been a while - did you get a chance to make some progress on
> >>>>>> this?  Do you need any help to unblock you?
> >>>>>>
> >>>>>
> >>>>> Sorry again, I'm back now. Trying to fix locking problems.
> >>>>> Added this to each function for analysis how the functions are called wrt.
> >>>>> locking:
> >>>>>
> >>>>> 	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));
> >>>>
> >>>> Do you have your code somewhere that we can look at ?
> >>>
> >>> This is the current version with debug printks. I've also added dump_stack()
> >>> to find out the code path but haven't analyzed the output yet.
> >>
> >> Can you send a proper patch ? Or a link to a git tree ? That is easier to
> >> handle than pasted code in an email...
> > 
> > Patch against what? I don't have a git server.
> 
> patch against current 6.1-rc, or against an older kernel should be OK too.
> But please "git send-email" a patch, or push your dev tree to github ?
> 
> > I've done some call trace analysis. These code paths are calling
> > pata_parport functions with ap->lock locked during init.
> > 
> > Comm: kworker, Workqueue: ata_sff ata_sff_pio_task
> > ata_sff_hsm_move -> ata_pio_sectors-> ata_sff_altstatus -> pata_parport_tf_read -> pata_parport_check_altstatus
> > ata_sff_hsm_move -> ata_sff_altstatus -> pata_parport_tf_read -> pata_parport_check_altstatus
> > ata_sff_pio_task -> ata_sff_busy_wait -> pata_parport_check_status
> > ata_sff_hsm_move -> ata_wait_idle -> ata_sff_busy_wait -> pata_parport_check_status
> > ata_sff_hsm_move -> ata_hsm_qc_complete -> ata_sff_irq_on -> ata_wait_idle -> ata_sff_busy_wait -> pata_parport_check_status
> > ata_sff_pio_task -> ata_sff_hsm_move -> ata_pio_sectors -> ata_pio_sector -> ata_pio_xfer -> pata_parport_data_xfer
> > ata_sff_pio_task -> ata_sff_hsm_move -> pata_parport_data_xfer
> > ata_sff_pio_task -> ata_sff_hsm_move -> pata_parport_tf_read
> > ata_sff_hsm_move -> ata_hsm_qc_complete -> ata_qc_complete -> fill_result_tf -> ata_sff_qc_fill_rtf -> pata_parport_tf_read
> > ata_sff_hsm_move -> ata_pio_sectors -> ata_sff_altstatus -> pata_parport_check_altstatus
> > ata_sff_hsm_move -> ata_sff_altstatus -> pata_parport_check_altstatus
> > 
> > Comm: modprobe
> > ata_host_start -> ata_eh_freeze_port -> ata_sff_freeze -> pata_parport_check_status
> > 
> > Comm: scsi_eh_4
> > ata_eh_recover -> ata_eh_reset -> ata_eh_thaw_port -> ata_sff_thaw -> ata_sff_irq_on -> ata_wait_idle -> ata_sff_busy_wait -> pata_parport_check_status
> > ata_eh_reset -> ata_eh_freeze_port -> ata_sff_freeze -> pata_parport_check_status
> > ata_scsi_error -> ata_scsi_port_error_handler -> ata_port_freeze -> ata_sff_freeze -> pata_parport_check_status
> > ata_sff_error_handler -> pata_parport_drain_fifo -> pata_parport_check_status
> 
> What exactly are the issues you are having with ap->lock ? It looks like
> you have done a lot of analysis of the code, but without any context about
> the problem, I do not understand what I am looking at.
> 

The problem is that pi_connect() can sleep because it calls
parport_claim_or_block(). And any access (even reading ATA status register)
requires pi_connect.

-- 
Ondrej Zary