linux-kernel - Re: [PATCH 2/7] ACPI / scan: Introduce common code for ACPI-based device hotplug

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Date:	Wed, 20 Feb 2013 13:23:34 -0700
From:	Toshi Kani <toshi.kani@...com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>, Jiang Liu <liuj97@...il.com>
Subject: Re: [PATCH 2/7] ACPI / scan: Introduce common code for ACPI-based
 device hotplug

On Wed, 2013-02-20 at 14:23 +0100, Rafael J. Wysocki wrote:
> On Tuesday, February 19, 2013 03:43:08 PM Yasuaki Ishimatsu wrote:
 :
> > 
> > > -	status = acpi_os_hotplug_execute(acpi_bus_hot_remove_device, ej_event);
> > > -	if (ACPI_FAILURE(status)) {
> > > -		put_device(&acpi_device->dev);
> > > -		kfree(ej_event);
> > > +	acpi_evaluate_hotplug_ost(acpi_device->handle, ost_source,
> > > +				  ACPI_OST_SC_EJECT_IN_PROGRESS, NULL);
> > > +	get_device(&acpi_device->dev);
> > > +	ret = acpi_scan_hot_remove(acpi_device);
> > 
> > Why don't you use acpi_os_hotplug_execute()? Do you have some reason?
> 
> Yes, I do.  acpi_eject_store() is run in a separate thread anyway (started by
> user space), so there's no need to use the workqueue for delayed execution here
> and we are under acpi_scan_lock anyway, so there shouldn't be any concurrency
> issues.

Well, there is an issue...  I just tested your patchset and hit the
following hang when I tried to delete a container through its sysfs
eject.  This thread got stuck in trying to delete the sysfs eject file
of the container.  I believe this is because the shell is still opening
this sysfs eject file.

PID: 1518   TASK: ffff88005f09c950  CPU: 1   COMMAND: "bash"
 #0 [ffff88003392baf8] __schedule at ffffffff8151ba75
 #1 [ffff88003392bb70] schedule at ffffffff8151bdc7
 #2 [ffff88003392bb80] schedule_timeout at ffffffff8151aa55
 #3 [ffff88003392bc00] wait_for_common at ffffffff8151bc43
 #4 [ffff88003392bc70] wait_for_completion at ffffffff8151bd60
 #5 [ffff88003392bc80] sysfs_addrm_finish at ffffffff811984ad
 #6 [ffff88003392bcd0] sysfs_hash_and_remove at ffffffff81196deb
 #7 [ffff88003392bd10] sysfs_remove_file at ffffffff81197051
 #8 [ffff88003392bd40] device_remove_file at ffffffff81332950
 #9 [ffff88003392bd50] acpi_device_unregister at ffffffff812a0556
#10 [ffff88003392bd80] acpi_bus_remove at ffffffff812a0658
#11 [ffff88003392bda0] acpi_bus_trim at ffffffff812a090e
#12 [ffff88003392bdd0] acpi_scan_hot_remove at ffffffff812a09c9
#13 [ffff88003392be30] acpi_eject_store at ffffffff812a0b45
#14 [ffff88003392be70] dev_attr_store at ffffffff81332038
#15 [ffff88003392be80] sysfs_write_file at ffffffff81197212
#16 [ffff88003392bee0] vfs_write at ffffffff8113a3cb
#17 [ffff88003392bf20] sys_write at ffffffff8113a5fd
#18 [ffff88003392bf80] system_call_fastpath at ffffffff81523759
    RIP: 00000033a16e4950  RSP: 00007fff4a5f5368  RFLAGS: 00000206
    RAX: 0000000000000001  RBX: ffffffff81523759  RCX: ffffffffffffffff
    RDX: 0000000000000002  RSI: 00007f2f8a3d8000  RDI: 0000000000000001
    RBP: 00007f2f8a3d8000   R8: 000000000000000a   R9: 00007f2f8a3c4740
    R10: 00007f2f8a3c4740  R11: 0000000000000246  R12: 00000033a19b1260
    R13: 0000000000000002  R14: ffff880000000000  R15: ffff88003395d680
    ORIG_RAX: 0000000000000001  CS: 0033  SS: 002b

Thanks,
-Toshi


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