linux-kernel - Re: [PATCH] qla2xxx: avoid maybe

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Message-ID: <1458078554.2375.97.camel@linux.vnet.ibm.com>
Date:	Tue, 15 Mar 2016 14:49:14 -0700
From:	James Bottomley <jejb@...ux.vnet.ibm.com>
To:	Arnd Bergmann <arnd@...db.de>, qla2xxx-upstream@...gic.com,
	"Martin K. Petersen" <martin.petersen@...cle.com>
Cc:	Nicholas Bellinger <nab@...ux-iscsi.org>,
	Himanshu Madhani <himanshu.madhani@...gic.com>,
	Quinn Tran <quinn.tran@...gic.com>,
	Alexei Potashnik <alexei@...estorage.com>,
	Bart Van Assche <bart.vanassche@...disk.com>,
	Swapnil Nagle <swapnil.nagle@...estorage.com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] qla2xxx: avoid maybe_uninitialized warning

On Tue, 2016-03-15 at 22:40 +0100, Arnd Bergmann wrote:
> The qlt_check_reserve_free_req() function produces an incorrect 
> warning when CONFIG_PROFILE_ANNOTATED_BRANCHES is set:
> 
> drivers/scsi/qla2xxx/qla_target.c: In function
> 'qlt_check_reserve_free_req':
> drivers/scsi/qla2xxx/qla_target.c:1887:3: error: 'cnt_in' may be used
> uninitialized in this function [-Werror=maybe-uninitialized]
>    ql_dbg(ql_dbg_io, vha, 0x305a,
>    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>        "qla_target(%d): There is no room in the request ring: vha
> ->req->ring_index=%d, vha->req->cnt=%d, req_cnt=%d Req-out=%d Req
> -in=%d Req-Length=%d\n",
>       
>  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ~~~~~~~~~~
>        vha->vp_idx, vha->req->ring_index,
>        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>        vha->req->cnt, req_cnt, cnt, cnt_in, vha->req->length);
>        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/scsi/qla2xxx/qla_target.c:1887:3: error: 'cnt' may be used
> uninitialized in this function [-Werror=maybe-uninitialized]
> 
> The problem is that gcc fails to track the state of the condition 
> across an annotated branch.
> 
> This slightly rearranges the code to move the second if() block
> into the first one, to avoid the warning while retaining the
> behavior of the code.

I thought our usual policy was to ask someone to fix the compiler when
it emitted a spurious warning.

James