linux-kernel - Re: [PATCH 7/9] scsi: megaraid_sas - Driver created the self work queue for OCR

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Message-ID: <4CF63D45.8020608@redhat.com>
Date:	Wed, 01 Dec 2010 13:19:17 +0100
From:	Tomas Henzl <thenzl@...hat.com>
To:	"Yang, Bo" <Bo.Yang@....com>
CC:	"'James.Bottomley@...senPartnership.com'" 
	<James.Bottomley@...senPartnership.com>,
	"'linux-scsi@...r.kernel.org'" <linux-scsi@...r.kernel.org>,
	"'akpm@...l.org'" <akpm@...l.org>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 7/9] scsi: megaraid_sas - Driver created the self work
 queue for OCR

On 11/30/2010 07:05 PM, Yang, Bo wrote:
> Tomas,
>
> In which case megasas_ocr_wq will hit NULL if create_workqueue create work queue success? If create_workqueue failed, OCR may have the problem.  But do you know if create_workqueue has the number limitation for creating work queues (how many work queue can it created? 10 or 20)?
>   
+	megasas_ocr_wq = create_workqueue("megasas_ocr");
+
+	if ( !megasas_ocr_wq )
+		printk(KERN_DEBUG "megasas: Failed to create workqueue.\n");

Then why do you check the return value if it can not fail?

You are allocating a lot of resources in the init function and when some of them is not 
available (which is unlikely) you return with an error value. Why don't you want that for 
create_workqueue too?

Is it safe enter the suspend mode with the workqueue still doing some job?
Shouldn't be the workqueue flushed in the suspend function?
 

> Thanks,
>
> Bo Yang
>
> -----Original Message-----
> From: Tomas Henzl [mailto:thenzl@...hat.com]
> Sent: Tuesday, November 30, 2010 11:11 AM 
> To: Yang, Bo
> Cc: 'James.Bottomley@...senPartnership.com'; 'linux-scsi@...r.kernel.org'; 'akpm@...l.org'; 'linux-kernel@...r.kernel.org'
> Subject: Re: [PATCH 7/9] scsi: megaraid_sas - Driver created the self work queue for OCR
>
> On 11/19/2010 06:37 PM, Yang, Bo wrote:
>   
>> Driver created the owner work queue (don't use global work queue). This queue will be used for online controller reset routine.
>>
>> Signed-off-by Bo Yang<bo.yang@....com>
>>
>> ---
>> drivers/scsi/megaraid/megaraid_sas.c |   13 ++++++++++++-
>>  1 file changed, 12 insertions(+), 1 deletion(-)
>>   
>> diff -rupN old/drivers/scsi/megaraid/megaraid_sas.c
>> new/drivers/scsi/megaraid/megaraid_sas.c ---
>> old/drivers/scsi/megaraid/megaraid_sas.c 2010-11-17 13:46:11.000000000
>> -0500 +++ new/drivers/scsi/megaraid/megaraid_sas.c 2010-11-17
>> 13:47:46.000000000 -0500 @@ -108,6 +108,7 @@ static struct
>> megasas_mgmt_info megasas_ static struct fasync_struct
>> *megasas_async_queue; static DEFINE_MUTEX(megasas_async_queue_mutex);
>> +static struct workqueue_struct *megasas_ocr_wq; static int
>> megasas_poll_wait_aen; static
>> DECLARE_WAIT_QUEUE_HEAD(megasas_poll_wait); static u32
>> support_poll_for_event; @@ -2435,7 +2436,7 @@
>> megasas_deplete_reply_queue(struct megas printk(KERN_NOTICE "megasas:
>> fwState=%x, stage:%d\n", fw_state, instance->adprecovery); -
>> schedule_work(&instance->work_init); + queue_work(megasas_ocr_wq,
>> &instance->work_init); return IRQ_HANDLED; } else { @@ -5157,6
>> +5158,11 @@ static int __init megasas_init(void) goto err_pcidrv; } +
>> megasas_ocr_wq = create_workqueue("megasas_ocr"); + + if (
>> !megasas_ocr_wq ) + printk(KERN_DEBUG "megasas: Failed to create
>> workqueue.\n"); + 
>>     
> What happens later, when you pass the null pointer to the queue_work ?
> I'm not sure this will work.
>
>   
>> rval = driver_create_file(&megasas_pci_driver.driver,
>> &driver_attr_version); if (rval) @@ -5228,6 +5234,11 @@ static void
>> __exit megasas_exit(void) &driver_attr_release_date);
>> driver_remove_file(&megasas_pci_driver.driver, &driver_attr_version);
>> + if (megasas_ocr_wq) { + destroy_workqueue(megasas_ocr_wq); +
>> megasas_ocr_wq = NULL; + } +
>> pci_unregister_driver(&megasas_pci_driver);
>> unregister_chrdev(megasas_mgmt_majorno, "megaraid_sas_ioctl"); } 
>>     
> --
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>   

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