* Re: [PATCH v2] ataflop: remove ataflop_probe_lock mutex
2021-10-17 2:09 ` [PATCH v2] ataflop: remove ataflop_probe_lock mutex Tetsuo Handa
@ 2021-10-17 19:05 ` Michael Schmitz
2021-10-17 23:47 ` Michael Schmitz
2021-10-18 22:25 ` Michael Schmitz
2021-10-21 16:20 ` Luis Chamberlain
2 siblings, 1 reply; 10+ messages in thread
From: Michael Schmitz @ 2021-10-17 19:05 UTC (permalink / raw)
To: Tetsuo Handa, linux-block, linux-m68k, Christoph Hellwig,
Luis Chamberlain, Finn Thain
Hi Tetsuo,
On 17/10/21 15:09, Tetsuo Handa wrote:
> Commit bf9c0538e485b591 ("ataflop: use a separate gendisk for each media
> format") introduced ataflop_probe_lock mutex, but forgot to unlock the
> mutex when atari_floppy_init() (i.e. module loading) succeeded. This will
> result in double lock deadlock if ataflop_probe() is called. Also,
> unregister_blkdev() must not be called from atari_floppy_init() with
> ataflop_probe_lock held when atari_floppy_init() failed, for
> ataflop_probe() waits for ataflop_probe_lock with major_names_lock held
> (i.e. AB-BA deadlock).
>
> __register_blkdev() needs to be called last in order to avoid calling
> ataflop_probe() when atari_floppy_init() is about to fail, for memory for
> completing already-started ataflop_probe() safely will be released as soon
> as atari_floppy_init() released ataflop_probe_lock mutex.
>
> As with commit 8b52d8be86d72308 ("loop: reorder loop_exit"),
> unregister_blkdev() needs to be called first in order to avoid calling
> ataflop_alloc_disk() from ataflop_probe() after del_gendisk() from
> atari_floppy_exit().
>
> By relocating __register_blkdev() / unregister_blkdev() as explained above,
> we can remove ataflop_probe_lock mutex, for probe function and __exit
> function are serialized by major_names_lock mutex.
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Fixes: bf9c0538e485b591 ("ataflop: use a separate gendisk for each media format")
> ---
> Changes in v2:
> Remove ataflop_probe_lock mutex than unlocking.
>
> Finn Thain wrote:
>> So I wonder if it would have been possible to use Aranym to find the
>> regression, or avoid it in the first place?
>
> OK, there is an emulator for testing this module. But I'm not familiar
> with m68k environment. Luis Chamberlain is proposing patchset for adding
> add_disk() error handling. I think that an answer would be to include
> m68k's mailing list into a patch for this module in order to notify of
> changes and expect m68k developers to review/test the patch.
>
> Michael Schmitz wrote:
>> Not as a module, no. I use the Atari floppy driver built-in. Latest kernel version I ran was 5.13.
>
> Great. Can you try this patch alone?
Doesn't appear to work, sorry.
Regards,
Michael Schmitz
>
> drivers/block/ataflop.c | 55 ++++++++++++++++++++---------------------
> 1 file changed, 27 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
> index a093644ac39f..adfe198e4699 100644
> --- a/drivers/block/ataflop.c
> +++ b/drivers/block/ataflop.c
> @@ -1986,8 +1986,6 @@ static int ataflop_alloc_disk(unsigned int drive, unsigned int type)
> return 0;
> }
>
> -static DEFINE_MUTEX(ataflop_probe_lock);
> -
> static void ataflop_probe(dev_t dev)
> {
> int drive = MINOR(dev) & 3;
> @@ -1998,12 +1996,30 @@ static void ataflop_probe(dev_t dev)
>
> if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS)
> return;
> - mutex_lock(&ataflop_probe_lock);
> if (!unit[drive].disk[type]) {
> if (ataflop_alloc_disk(drive, type) == 0)
> add_disk(unit[drive].disk[type]);
> }
> - mutex_unlock(&ataflop_probe_lock);
> +}
> +
> +static void atari_floppy_cleanup(void)
> +{
> + int i;
> + int type;
> +
> + for (i = 0; i < FD_MAX_UNITS; i++) {
> + for (type = 0; type < NUM_DISK_MINORS; type++) {
> + if (!unit[i].disk[type])
> + continue;
> + del_gendisk(unit[i].disk[type]);
> + blk_cleanup_queue(unit[i].disk[type]->queue);
> + put_disk(unit[i].disk[type]);
> + }
> + blk_mq_free_tag_set(&unit[i].tag_set);
> + }
> +
> + del_timer_sync(&fd_timer);
> + atari_stram_free(DMABuffer);
> }
>
> static int __init atari_floppy_init (void)
> @@ -2015,11 +2031,6 @@ static int __init atari_floppy_init (void)
> /* Amiga, Mac, ... don't have Atari-compatible floppy :-) */
> return -ENODEV;
>
> - mutex_lock(&ataflop_probe_lock);
> - ret = __register_blkdev(FLOPPY_MAJOR, "fd", ataflop_probe);
> - if (ret)
> - goto out_unlock;
> -
> for (i = 0; i < FD_MAX_UNITS; i++) {
> memset(&unit[i].tag_set, 0, sizeof(unit[i].tag_set));
> unit[i].tag_set.ops = &ataflop_mq_ops;
> @@ -2072,7 +2083,12 @@ static int __init atari_floppy_init (void)
> UseTrackbuffer ? "" : "no ");
> config_types();
>
> - return 0;
> + ret = __register_blkdev(FLOPPY_MAJOR, "fd", ataflop_probe);
> + if (ret) {
> + printk(KERN_ERR "atari_floppy_init: cannot register block device\n");
> + atari_floppy_cleanup();
> + }
> + return ret;
>
> err:
> while (--i >= 0) {
> @@ -2081,9 +2097,6 @@ static int __init atari_floppy_init (void)
> blk_mq_free_tag_set(&unit[i].tag_set);
> }
>
> - unregister_blkdev(FLOPPY_MAJOR, "fd");
> -out_unlock:
> - mutex_unlock(&ataflop_probe_lock);
> return ret;
> }
>
> @@ -2128,22 +2141,8 @@ __setup("floppy=", atari_floppy_setup);
>
> static void __exit atari_floppy_exit(void)
> {
> - int i, type;
> -
> - for (i = 0; i < FD_MAX_UNITS; i++) {
> - for (type = 0; type < NUM_DISK_MINORS; type++) {
> - if (!unit[i].disk[type])
> - continue;
> - del_gendisk(unit[i].disk[type]);
> - blk_cleanup_queue(unit[i].disk[type]->queue);
> - put_disk(unit[i].disk[type]);
> - }
> - blk_mq_free_tag_set(&unit[i].tag_set);
> - }
> unregister_blkdev(FLOPPY_MAJOR, "fd");
> -
> - del_timer_sync(&fd_timer);
> - atari_stram_free( DMABuffer );
> + atari_floppy_cleanup();
> }
>
> module_init(atari_floppy_init)
>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2] ataflop: remove ataflop_probe_lock mutex
2021-10-17 19:05 ` Michael Schmitz
@ 2021-10-17 23:47 ` Michael Schmitz
2021-10-18 8:15 ` Michael Schmitz
0 siblings, 1 reply; 10+ messages in thread
From: Michael Schmitz @ 2021-10-17 23:47 UTC (permalink / raw)
To: Tetsuo Handa, linux-block, linux-m68k, Christoph Hellwig,
Luis Chamberlain, Finn Thain
Hi Tetsuo,
nevermind - stock 5.9 doesn't work either (mount hangs indefinitely).
Might have to do with format autoprobing - I'll try that next.
Cheers,
Michael
On 18/10/21 08:05, Michael Schmitz wrote:
>> Michael Schmitz wrote:
>>> Not as a module, no. I use the Atari floppy driver built-in. Latest
>>> kernel version I ran was 5.13.
>>
>> Great. Can you try this patch alone?
>
> Doesn't appear to work, sorry.
>
> Regards,
>
> Michael Schmitz
>
>>
>> drivers/block/ataflop.c | 55 ++++++++++++++++++++---------------------
>> 1 file changed, 27 insertions(+), 28 deletions(-)
>>
>> diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
>> index a093644ac39f..adfe198e4699 100644
>> --- a/drivers/block/ataflop.c
>> +++ b/drivers/block/ataflop.c
>> @@ -1986,8 +1986,6 @@ static int ataflop_alloc_disk(unsigned int
>> drive, unsigned int type)
>> return 0;
>> }
>>
>> -static DEFINE_MUTEX(ataflop_probe_lock);
>> -
>> static void ataflop_probe(dev_t dev)
>> {
>> int drive = MINOR(dev) & 3;
>> @@ -1998,12 +1996,30 @@ static void ataflop_probe(dev_t dev)
>>
>> if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS)
>> return;
>> - mutex_lock(&ataflop_probe_lock);
>> if (!unit[drive].disk[type]) {
>> if (ataflop_alloc_disk(drive, type) == 0)
>> add_disk(unit[drive].disk[type]);
>> }
>> - mutex_unlock(&ataflop_probe_lock);
>> +}
>> +
>> +static void atari_floppy_cleanup(void)
>> +{
>> + int i;
>> + int type;
>> +
>> + for (i = 0; i < FD_MAX_UNITS; i++) {
>> + for (type = 0; type < NUM_DISK_MINORS; type++) {
>> + if (!unit[i].disk[type])
>> + continue;
>> + del_gendisk(unit[i].disk[type]);
>> + blk_cleanup_queue(unit[i].disk[type]->queue);
>> + put_disk(unit[i].disk[type]);
>> + }
>> + blk_mq_free_tag_set(&unit[i].tag_set);
>> + }
>> +
>> + del_timer_sync(&fd_timer);
>> + atari_stram_free(DMABuffer);
>> }
>>
>> static int __init atari_floppy_init (void)
>> @@ -2015,11 +2031,6 @@ static int __init atari_floppy_init (void)
>> /* Amiga, Mac, ... don't have Atari-compatible floppy :-) */
>> return -ENODEV;
>>
>> - mutex_lock(&ataflop_probe_lock);
>> - ret = __register_blkdev(FLOPPY_MAJOR, "fd", ataflop_probe);
>> - if (ret)
>> - goto out_unlock;
>> -
>> for (i = 0; i < FD_MAX_UNITS; i++) {
>> memset(&unit[i].tag_set, 0, sizeof(unit[i].tag_set));
>> unit[i].tag_set.ops = &ataflop_mq_ops;
>> @@ -2072,7 +2083,12 @@ static int __init atari_floppy_init (void)
>> UseTrackbuffer ? "" : "no ");
>> config_types();
>>
>> - return 0;
>> + ret = __register_blkdev(FLOPPY_MAJOR, "fd", ataflop_probe);
>> + if (ret) {
>> + printk(KERN_ERR "atari_floppy_init: cannot register block
>> device\n");
>> + atari_floppy_cleanup();
>> + }
>> + return ret;
>>
>> err:
>> while (--i >= 0) {
>> @@ -2081,9 +2097,6 @@ static int __init atari_floppy_init (void)
>> blk_mq_free_tag_set(&unit[i].tag_set);
>> }
>>
>> - unregister_blkdev(FLOPPY_MAJOR, "fd");
>> -out_unlock:
>> - mutex_unlock(&ataflop_probe_lock);
>> return ret;
>> }
>>
>> @@ -2128,22 +2141,8 @@ __setup("floppy=", atari_floppy_setup);
>>
>> static void __exit atari_floppy_exit(void)
>> {
>> - int i, type;
>> -
>> - for (i = 0; i < FD_MAX_UNITS; i++) {
>> - for (type = 0; type < NUM_DISK_MINORS; type++) {
>> - if (!unit[i].disk[type])
>> - continue;
>> - del_gendisk(unit[i].disk[type]);
>> - blk_cleanup_queue(unit[i].disk[type]->queue);
>> - put_disk(unit[i].disk[type]);
>> - }
>> - blk_mq_free_tag_set(&unit[i].tag_set);
>> - }
>> unregister_blkdev(FLOPPY_MAJOR, "fd");
>> -
>> - del_timer_sync(&fd_timer);
>> - atari_stram_free( DMABuffer );
>> + atari_floppy_cleanup();
>> }
>>
>> module_init(atari_floppy_init)
>>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2] ataflop: remove ataflop_probe_lock mutex
2021-10-17 23:47 ` Michael Schmitz
@ 2021-10-18 8:15 ` Michael Schmitz
0 siblings, 0 replies; 10+ messages in thread
From: Michael Schmitz @ 2021-10-18 8:15 UTC (permalink / raw)
To: Tetsuo Handa, linux-block, linux-m68k, Christoph Hellwig,
Luis Chamberlain, Finn Thain
Hi Tetsuo,
the ataflop driver got broken in commit 6ec3938cff95f (ataflop: convert
to blk-mq), three years ago. Can't remember seeing that one before.
Looking at a debug log, I get:
[ 7919.150000] fd_open: type=0
[ 7919.180000] Queue request: drive 0 type 0
[ 7919.200000] Request params: Si=0 Tr=0 Se=1 Data=00541000
[ 7919.200000] do_fd_action
[ 7919.200000] fd_rwsec(), Sec=1, Access=r
[ 7919.200000] finish_fdc: dummy seek started
[ 7920.550000] FDC irq, status = a0 handler = 001ea00a
[ 7920.550000] finish_fdc_done entered
[ 7920.550000] finish_fdc() finished
I would have expected an interrupt from fd_rwsec() (which sets
fd_rwsec_done() as IRQ handler), but calling finish_fdc() from the
request function while interrupts for the controller are disabled but a
request is in-flight pretty much ensures we never see fd_rwsec_done()
called:
ReqCnt = 0;
ReqCmd = rq_data_dir(fd_request);
ReqBlock = blk_rq_pos(fd_request);
ReqBuffer = bio_data(fd_request->bio);
setup_req_params( drive );
do_fd_action( drive );
if (bd->last)
finish_fdc();
atari_enable_irq( IRQ_MFP_FDC );
The old driver used a wait queue to serialize requests, and only called
finish_fdc() when no further requests were pending. I wonder how to make
sure finish_fdc() only gets called in the same situation now ...
bd->last clearly isn't the right hint here.
I suspect this isn't the only thing that broke...
Cheers,
Michael
On 18/10/21 12:47, Michael Schmitz wrote:
> Hi Tetsuo,
>
> nevermind - stock 5.9 doesn't work either (mount hangs indefinitely).
>
> Might have to do with format autoprobing - I'll try that next.
>
> Cheers,
>
> Michael
>
>
> On 18/10/21 08:05, Michael Schmitz wrote:
>>> Michael Schmitz wrote:
>>>> Not as a module, no. I use the Atari floppy driver built-in. Latest
>>>> kernel version I ran was 5.13.
>>>
>>> Great. Can you try this patch alone?
>>
>> Doesn't appear to work, sorry.
>>
>> Regards,
>>
>> Michael Schmitz
>>
>>>
>>> drivers/block/ataflop.c | 55 ++++++++++++++++++++---------------------
>>> 1 file changed, 27 insertions(+), 28 deletions(-)
>>>
>>> diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
>>> index a093644ac39f..adfe198e4699 100644
>>> --- a/drivers/block/ataflop.c
>>> +++ b/drivers/block/ataflop.c
>>> @@ -1986,8 +1986,6 @@ static int ataflop_alloc_disk(unsigned int
>>> drive, unsigned int type)
>>> return 0;
>>> }
>>>
>>> -static DEFINE_MUTEX(ataflop_probe_lock);
>>> -
>>> static void ataflop_probe(dev_t dev)
>>> {
>>> int drive = MINOR(dev) & 3;
>>> @@ -1998,12 +1996,30 @@ static void ataflop_probe(dev_t dev)
>>>
>>> if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS)
>>> return;
>>> - mutex_lock(&ataflop_probe_lock);
>>> if (!unit[drive].disk[type]) {
>>> if (ataflop_alloc_disk(drive, type) == 0)
>>> add_disk(unit[drive].disk[type]);
>>> }
>>> - mutex_unlock(&ataflop_probe_lock);
>>> +}
>>> +
>>> +static void atari_floppy_cleanup(void)
>>> +{
>>> + int i;
>>> + int type;
>>> +
>>> + for (i = 0; i < FD_MAX_UNITS; i++) {
>>> + for (type = 0; type < NUM_DISK_MINORS; type++) {
>>> + if (!unit[i].disk[type])
>>> + continue;
>>> + del_gendisk(unit[i].disk[type]);
>>> + blk_cleanup_queue(unit[i].disk[type]->queue);
>>> + put_disk(unit[i].disk[type]);
>>> + }
>>> + blk_mq_free_tag_set(&unit[i].tag_set);
>>> + }
>>> +
>>> + del_timer_sync(&fd_timer);
>>> + atari_stram_free(DMABuffer);
>>> }
>>>
>>> static int __init atari_floppy_init (void)
>>> @@ -2015,11 +2031,6 @@ static int __init atari_floppy_init (void)
>>> /* Amiga, Mac, ... don't have Atari-compatible floppy :-) */
>>> return -ENODEV;
>>>
>>> - mutex_lock(&ataflop_probe_lock);
>>> - ret = __register_blkdev(FLOPPY_MAJOR, "fd", ataflop_probe);
>>> - if (ret)
>>> - goto out_unlock;
>>> -
>>> for (i = 0; i < FD_MAX_UNITS; i++) {
>>> memset(&unit[i].tag_set, 0, sizeof(unit[i].tag_set));
>>> unit[i].tag_set.ops = &ataflop_mq_ops;
>>> @@ -2072,7 +2083,12 @@ static int __init atari_floppy_init (void)
>>> UseTrackbuffer ? "" : "no ");
>>> config_types();
>>>
>>> - return 0;
>>> + ret = __register_blkdev(FLOPPY_MAJOR, "fd", ataflop_probe);
>>> + if (ret) {
>>> + printk(KERN_ERR "atari_floppy_init: cannot register block
>>> device\n");
>>> + atari_floppy_cleanup();
>>> + }
>>> + return ret;
>>>
>>> err:
>>> while (--i >= 0) {
>>> @@ -2081,9 +2097,6 @@ static int __init atari_floppy_init (void)
>>> blk_mq_free_tag_set(&unit[i].tag_set);
>>> }
>>>
>>> - unregister_blkdev(FLOPPY_MAJOR, "fd");
>>> -out_unlock:
>>> - mutex_unlock(&ataflop_probe_lock);
>>> return ret;
>>> }
>>>
>>> @@ -2128,22 +2141,8 @@ __setup("floppy=", atari_floppy_setup);
>>>
>>> static void __exit atari_floppy_exit(void)
>>> {
>>> - int i, type;
>>> -
>>> - for (i = 0; i < FD_MAX_UNITS; i++) {
>>> - for (type = 0; type < NUM_DISK_MINORS; type++) {
>>> - if (!unit[i].disk[type])
>>> - continue;
>>> - del_gendisk(unit[i].disk[type]);
>>> - blk_cleanup_queue(unit[i].disk[type]->queue);
>>> - put_disk(unit[i].disk[type]);
>>> - }
>>> - blk_mq_free_tag_set(&unit[i].tag_set);
>>> - }
>>> unregister_blkdev(FLOPPY_MAJOR, "fd");
>>> -
>>> - del_timer_sync(&fd_timer);
>>> - atari_stram_free( DMABuffer );
>>> + atari_floppy_cleanup();
>>> }
>>>
>>> module_init(atari_floppy_init)
>>>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2] ataflop: remove ataflop_probe_lock mutex
2021-10-17 2:09 ` [PATCH v2] ataflop: remove ataflop_probe_lock mutex Tetsuo Handa
2021-10-17 19:05 ` Michael Schmitz
@ 2021-10-18 22:25 ` Michael Schmitz
2021-10-21 16:20 ` Luis Chamberlain
2 siblings, 0 replies; 10+ messages in thread
From: Michael Schmitz @ 2021-10-18 22:25 UTC (permalink / raw)
To: Tetsuo Handa, linux-block, linux-m68k, Christoph Hellwig,
Luis Chamberlain, Finn Thain
Hi Tetsu,
On 17/10/21 15:09, Tetsuo Handa wrote:
> Commit bf9c0538e485b591 ("ataflop: use a separate gendisk for each media
> format") introduced ataflop_probe_lock mutex, but forgot to unlock the
> mutex when atari_floppy_init() (i.e. module loading) succeeded. This will
> result in double lock deadlock if ataflop_probe() is called. Also,
> unregister_blkdev() must not be called from atari_floppy_init() with
> ataflop_probe_lock held when atari_floppy_init() failed, for
> ataflop_probe() waits for ataflop_probe_lock with major_names_lock held
> (i.e. AB-BA deadlock).
>
> __register_blkdev() needs to be called last in order to avoid calling
> ataflop_probe() when atari_floppy_init() is about to fail, for memory for
> completing already-started ataflop_probe() safely will be released as soon
> as atari_floppy_init() released ataflop_probe_lock mutex.
>
> As with commit 8b52d8be86d72308 ("loop: reorder loop_exit"),
> unregister_blkdev() needs to be called first in order to avoid calling
> ataflop_alloc_disk() from ataflop_probe() after del_gendisk() from
> atari_floppy_exit().
>
> By relocating __register_blkdev() / unregister_blkdev() as explained above,
> we can remove ataflop_probe_lock mutex, for probe function and __exit
> function are serialized by major_names_lock mutex.
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Fixes: bf9c0538e485b591 ("ataflop: use a separate gendisk for each media format")
> ---
> Changes in v2:
> Remove ataflop_probe_lock mutex than unlocking.
>
> Finn Thain wrote:
>> So I wonder if it would have been possible to use Aranym to find the
>> regression, or avoid it in the first place?
>
> OK, there is an emulator for testing this module. But I'm not familiar
> with m68k environment. Luis Chamberlain is proposing patchset for adding
> add_disk() error handling. I think that an answer would be to include
> m68k's mailing list into a patch for this module in order to notify of
> changes and expect m68k developers to review/test the patch.
>
> Michael Schmitz wrote:
>> Not as a module, no. I use the Atari floppy driver built-in. Latest kernel version I ran was 5.13.
>
> Great. Can you try this patch alone?
Works, after fixing the ataflop_queue_rq() breakage (separate patch sent).
Tested-by: Michael Schmitz <schmitzmic@gmail.com>
Thanks,
Michael
>
> drivers/block/ataflop.c | 55 ++++++++++++++++++++---------------------
> 1 file changed, 27 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/block/ataflop.c b/drivers/block/ataflop.c
> index a093644ac39f..adfe198e4699 100644
> --- a/drivers/block/ataflop.c
> +++ b/drivers/block/ataflop.c
> @@ -1986,8 +1986,6 @@ static int ataflop_alloc_disk(unsigned int drive, unsigned int type)
> return 0;
> }
>
> -static DEFINE_MUTEX(ataflop_probe_lock);
> -
> static void ataflop_probe(dev_t dev)
> {
> int drive = MINOR(dev) & 3;
> @@ -1998,12 +1996,30 @@ static void ataflop_probe(dev_t dev)
>
> if (drive >= FD_MAX_UNITS || type >= NUM_DISK_MINORS)
> return;
> - mutex_lock(&ataflop_probe_lock);
> if (!unit[drive].disk[type]) {
> if (ataflop_alloc_disk(drive, type) == 0)
> add_disk(unit[drive].disk[type]);
> }
> - mutex_unlock(&ataflop_probe_lock);
> +}
> +
> +static void atari_floppy_cleanup(void)
> +{
> + int i;
> + int type;
> +
> + for (i = 0; i < FD_MAX_UNITS; i++) {
> + for (type = 0; type < NUM_DISK_MINORS; type++) {
> + if (!unit[i].disk[type])
> + continue;
> + del_gendisk(unit[i].disk[type]);
> + blk_cleanup_queue(unit[i].disk[type]->queue);
> + put_disk(unit[i].disk[type]);
> + }
> + blk_mq_free_tag_set(&unit[i].tag_set);
> + }
> +
> + del_timer_sync(&fd_timer);
> + atari_stram_free(DMABuffer);
> }
>
> static int __init atari_floppy_init (void)
> @@ -2015,11 +2031,6 @@ static int __init atari_floppy_init (void)
> /* Amiga, Mac, ... don't have Atari-compatible floppy :-) */
> return -ENODEV;
>
> - mutex_lock(&ataflop_probe_lock);
> - ret = __register_blkdev(FLOPPY_MAJOR, "fd", ataflop_probe);
> - if (ret)
> - goto out_unlock;
> -
> for (i = 0; i < FD_MAX_UNITS; i++) {
> memset(&unit[i].tag_set, 0, sizeof(unit[i].tag_set));
> unit[i].tag_set.ops = &ataflop_mq_ops;
> @@ -2072,7 +2083,12 @@ static int __init atari_floppy_init (void)
> UseTrackbuffer ? "" : "no ");
> config_types();
>
> - return 0;
> + ret = __register_blkdev(FLOPPY_MAJOR, "fd", ataflop_probe);
> + if (ret) {
> + printk(KERN_ERR "atari_floppy_init: cannot register block device\n");
> + atari_floppy_cleanup();
> + }
> + return ret;
>
> err:
> while (--i >= 0) {
> @@ -2081,9 +2097,6 @@ static int __init atari_floppy_init (void)
> blk_mq_free_tag_set(&unit[i].tag_set);
> }
>
> - unregister_blkdev(FLOPPY_MAJOR, "fd");
> -out_unlock:
> - mutex_unlock(&ataflop_probe_lock);
> return ret;
> }
>
> @@ -2128,22 +2141,8 @@ __setup("floppy=", atari_floppy_setup);
>
> static void __exit atari_floppy_exit(void)
> {
> - int i, type;
> -
> - for (i = 0; i < FD_MAX_UNITS; i++) {
> - for (type = 0; type < NUM_DISK_MINORS; type++) {
> - if (!unit[i].disk[type])
> - continue;
> - del_gendisk(unit[i].disk[type]);
> - blk_cleanup_queue(unit[i].disk[type]->queue);
> - put_disk(unit[i].disk[type]);
> - }
> - blk_mq_free_tag_set(&unit[i].tag_set);
> - }
> unregister_blkdev(FLOPPY_MAJOR, "fd");
> -
> - del_timer_sync(&fd_timer);
> - atari_stram_free( DMABuffer );
> + atari_floppy_cleanup();
> }
>
> module_init(atari_floppy_init)
>
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2] ataflop: remove ataflop_probe_lock mutex
2021-10-17 2:09 ` [PATCH v2] ataflop: remove ataflop_probe_lock mutex Tetsuo Handa
2021-10-17 19:05 ` Michael Schmitz
2021-10-18 22:25 ` Michael Schmitz
@ 2021-10-21 16:20 ` Luis Chamberlain
2021-10-21 16:21 ` Luis Chamberlain
2 siblings, 1 reply; 10+ messages in thread
From: Luis Chamberlain @ 2021-10-21 16:20 UTC (permalink / raw)
To: Tetsuo Handa
Cc: Michael Schmitz, linux-block, linux-m68k, Christoph Hellwig, Finn Thain
On Sun, Oct 17, 2021 at 11:09:47AM +0900, Tetsuo Handa wrote:
> Commit bf9c0538e485b591 ("ataflop: use a separate gendisk for each media
> format") introduced ataflop_probe_lock mutex, but forgot to unlock the
> mutex when atari_floppy_init() (i.e. module loading) succeeded. This will
> result in double lock deadlock if ataflop_probe() is called. Also,
> unregister_blkdev() must not be called from atari_floppy_init() with
> ataflop_probe_lock held when atari_floppy_init() failed, for
> ataflop_probe() waits for ataflop_probe_lock with major_names_lock held
> (i.e. AB-BA deadlock).
>
> __register_blkdev() needs to be called last in order to avoid calling
> ataflop_probe() when atari_floppy_init() is about to fail, for memory for
> completing already-started ataflop_probe() safely will be released as soon
> as atari_floppy_init() released ataflop_probe_lock mutex.
>
> As with commit 8b52d8be86d72308 ("loop: reorder loop_exit"),
> unregister_blkdev() needs to be called first in order to avoid calling
> ataflop_alloc_disk() from ataflop_probe() after del_gendisk() from
> atari_floppy_exit().
>
> By relocating __register_blkdev() / unregister_blkdev() as explained above,
> we can remove ataflop_probe_lock mutex, for probe function and __exit
> function are serialized by major_names_lock mutex.
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> Fixes: bf9c0538e485b591 ("ataflop: use a separate gendisk for each media format")
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Luis
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v2] ataflop: remove ataflop_probe_lock mutex
2021-10-21 16:20 ` Luis Chamberlain
@ 2021-10-21 16:21 ` Luis Chamberlain
0 siblings, 0 replies; 10+ messages in thread
From: Luis Chamberlain @ 2021-10-21 16:21 UTC (permalink / raw)
To: Tetsuo Handa
Cc: Michael Schmitz, linux-block, linux-m68k, Christoph Hellwig, Finn Thain
On Thu, Oct 21, 2021 at 09:20:06AM -0700, Luis Chamberlain wrote:
> On Sun, Oct 17, 2021 at 11:09:47AM +0900, Tetsuo Handa wrote:
> > Commit bf9c0538e485b591 ("ataflop: use a separate gendisk for each media
> > format") introduced ataflop_probe_lock mutex, but forgot to unlock the
> > mutex when atari_floppy_init() (i.e. module loading) succeeded. This will
> > result in double lock deadlock if ataflop_probe() is called. Also,
> > unregister_blkdev() must not be called from atari_floppy_init() with
> > ataflop_probe_lock held when atari_floppy_init() failed, for
> > ataflop_probe() waits for ataflop_probe_lock with major_names_lock held
> > (i.e. AB-BA deadlock).
> >
> > __register_blkdev() needs to be called last in order to avoid calling
> > ataflop_probe() when atari_floppy_init() is about to fail, for memory for
> > completing already-started ataflop_probe() safely will be released as soon
> > as atari_floppy_init() released ataflop_probe_lock mutex.
> >
> > As with commit 8b52d8be86d72308 ("loop: reorder loop_exit"),
> > unregister_blkdev() needs to be called first in order to avoid calling
> > ataflop_alloc_disk() from ataflop_probe() after del_gendisk() from
> > atari_floppy_exit().
> >
> > By relocating __register_blkdev() / unregister_blkdev() as explained above,
> > we can remove ataflop_probe_lock mutex, for probe function and __exit
> > function are serialized by major_names_lock mutex.
> >
> > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> > Fixes: bf9c0538e485b591 ("ataflop: use a separate gendisk for each media format")
>
> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
I should note though that this does not apply to linux-next, I rebased
it and will send a rebased version on my v3 series of my last patch set
for add_disk error handling work().
Luis
^ permalink raw reply [flat|nested] 10+ messages in thread