linux-kernel - RE: [PATCH] qed: Fix -Wmaybe-uninitialized false positive

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Message-ID: <MN2PR18MB318218F121EBE1144A4AA36EA1EA0@MN2PR18MB3182.namprd18.prod.outlook.com>
Date:   Tue, 18 Jun 2019 09:27:28 +0000
From:   Michal Kalderon <mkalderon@...vell.com>
To:     Arnd Bergmann <arnd@...db.de>, Ariel Elior <aelior@...vell.com>,
        GR-everest-linux-l2 <GR-everest-linux-l2@...vell.com>,
        "David S. Miller" <davem@...emloft.net>
CC:     Ariel Elior <aelior@...vell.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Denis Bolotin <dbolotin@...vell.com>,
        Tomer Tayar <tomer.tayar@...ium.com>,
        Sudarsana Reddy Kalluru <skalluru@...vell.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] qed: Fix -Wmaybe-uninitialized false positive

> From: Arnd Bergmann <arnd@...db.de>
> Sent: Monday, June 17, 2019 4:05 PM
> 
> A previous attempt to shut up the uninitialized variable use warning was
> apparently insufficient. When CONFIG_PROFILE_ANNOTATED_BRANCHES is
> set, gcc-8 still warns, because the unlikely() check in DP_NOTICE() causes it to
> no longer track the state of all variables correctly:
> 
> drivers/net/ethernet/qlogic/qed/qed_dev.c: In function
> 'qed_llh_set_ppfid_affinity':
> drivers/net/ethernet/qlogic/qed/qed_dev.c:798:47: error: 'abs_ppfid' may
> be used uninitialized in this function [-Werror=maybe-uninitialized]
>   addr = NIG_REG_PPF_TO_ENGINE_SEL + abs_ppfid * 0x4;
>                                      ~~~~~~~~~~^~~~~
> 
> This is not a nice workaround, but always initializing the output from
> qed_llh_abs_ppfid() at least shuts up the false positive reliably.
> 
> Fixes: 79284adeb99e ("qed: Add llh ppfid interface and 100g support for
> offload protocols")
> Fixes: 8e2ea3ea9625 ("qed: Fix static checker warning")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/net/ethernet/qlogic/qed/qed_dev.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/ethernet/qlogic/qed/qed_dev.c
> b/drivers/net/ethernet/qlogic/qed/qed_dev.c
> index eec7cb65c7e6..a1ebc2b1ca0b 100644
> --- a/drivers/net/ethernet/qlogic/qed/qed_dev.c
> +++ b/drivers/net/ethernet/qlogic/qed/qed_dev.c
> @@ -652,6 +652,7 @@ static int qed_llh_abs_ppfid(struct qed_dev *cdev, u8
> ppfid, u8 *p_abs_ppfid)
>  		DP_NOTICE(cdev,
>  			  "ppfid %d is not valid, available indices are
> 0..%hhd\n",
>  			  ppfid, p_llh_info->num_ppfid - 1);
> +		*p_abs_ppfid = 0;
>  		return -EINVAL;
>  	}
> 
> --
> 2.20.0

Thanks, 

Acked-by: Michal Kalderon <michal.kalderon@...vell.com>