Messages in this thread Patch in this message | | | Date | Wed, 25 May 2005 08:50:05 +0200 | From | Hannes Reinecke <> | Subject | Re: [PATCH] Fix reference counting for failed SCSI devices |
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James Bottomley wrote: > On Tue, 2005-05-24 at 11:38 +0200, Hannes Reinecke wrote: >>whenever the scsi-ml tries to scan non-existent devices the reference >>count in scsi_alloc_sdev() and scsi_probe_and_add_lun() is not adjusted >>properly. Every call to XXX_initialize in the driver core sets the >>reference count to 1, so for a proper deallocation an explicit XXX_put() >>has to be done. > > That's true, but I don't see what the problem is if the device has never > been made visible. > It's not visible but it's still allocated and referenced. So on doing a rmmod these class_devices are being deallocated which crashes as the class device is not connected properly.
>>+ put_device(&starget->dev); > > this would amount to a double put, since the parent put method is called > in the device release. > Oops. Correct.
>>+ class_device_put(&sdev->sdev_classdev); > > This is unnecessary since the class device is simply occupying a private > area in the scsi_device. As long as its never made visible to the > system, its refcount is irrelevant > It's not. Whenever you try to rmmod the adapter it becomes highly relevant. If it doesn't crash you've at least generated a memleak as the class device is never freed. (And these are quite a few for Wide-SCSI Double-channel adapters ...)
>> put_device(&sdev->sdev_gendev); >> out: >> if (display_failure_msg) >>@@ -855,6 +857,8 @@ static int scsi_probe_and_add_lun(struct >> if (sdev->host->hostt->slave_destroy) >> sdev->host->hostt->slave_destroy(sdev); >> transport_destroy_device(&sdev->sdev_gendev); >>+ class_device_put(&sdev->sdev_classdev); >>+ put_device(sdev->sdev_gendev.parent); > > same should apply here. As long as this cascade occurs before > scsi_add_lun() (which calls scsi_sysfs_add_sdev()), which is what makes > the whole set of devices and classes visible. > Correct for the parent device. The class device has to be deallocated properly if a rmmod should work properly.
New patch attached. Please apply.
Cheers,
Hannes -- Dr. Hannes Reinecke hare@suse.de SuSE Linux AG S390 & zSeries Maxfeldstraße 5 +49 911 74053 688 90409 Nürnberg http://www.suse.de From: Hannes Reinecke <hare@suse.de> Subject: Fix refcount for failed devices
When a non-present device is scanned it is not properly deregistered from the driver core. Calling XXX_initialize() functions from the driver core sets the reference count to 1, so for proper deallocation a XXX_put() has to be issued.
--- linux-2.6.12-rc4/drivers/scsi/scsi_scan.c.orig 2005-05-24 10:26:46.000000000 +0200 +++ linux-2.6.12-rc4/drivers/scsi/scsi_scan.c 2005-05-24 10:55:52.000000000 +0200 @@ -282,6 +282,7 @@ static struct scsi_device *scsi_alloc_sd out_device_destroy: transport_destroy_device(&sdev->sdev_gendev); scsi_free_queue(sdev->request_queue); + class_device_put(&sdev->sdev_classdev); put_device(&sdev->sdev_gendev); out: if (display_failure_msg) @@ -855,6 +856,7 @@ static int scsi_probe_and_add_lun(struct if (sdev->host->hostt->slave_destroy) sdev->host->hostt->slave_destroy(sdev); transport_destroy_device(&sdev->sdev_gendev); + class_device_put(&sdev->sdev_classdev); put_device(&sdev->sdev_gendev); } out: | |