linux-kernel - Re: [PATCH 1/2][next] RDMA/hns: fix comparison of unsigned long variable 'end' with less than zero

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Message-ID: <2046653d-bc90-d287-22a6-b9eaa2740b6e@huawei.com>
Date:   Tue, 9 Jul 2019 18:58:08 +0800
From:   oulijun <oulijun@...wei.com>
To:     Colin King <colin.king@...onical.com>,
        Wei Hu <xavier.huwei@...wei.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>, <linux-rdma@...r.kernel.org>
CC:     <kernel-janitors@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2][next] RDMA/hns: fix comparison of unsigned long
 variable 'end' with less than zero

在 2019/5/31 17:21, Colin King 写道:
> From: Colin Ian King <colin.king@...onical.com>
>
> Currently the comparison of end with less than zero is always false
> because end is an unsigned long.  Also, replace checks of end with
> non-zero with end > 0 as it is possible that the #defined decrement
> may be changed in the future causing end to step over zero and go
> negative.
>
> The initialization of end with 0 is also redundant as this value is
> never read and is later set to HW_SYNC_TIMEOUT_MSECS, so fix this by
> initializing it with this value to begin with.
>
> Addresses-Coverity: ("Unsigned compared against 0")
> Fixes: 669cefb654cb ("RDMA/hns: Remove jiffies operation in disable interrupt context")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/infiniband/hw/hns/hns_roce_hem.c   |  4 ++--
>  drivers/infiniband/hw/hns/hns_roce_hw_v1.c | 12 ++++++------
>  2 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/infiniband/hw/hns/hns_roce_hem.c b/drivers/infiniband/hw/hns/hns_roce_hem.c
> index 157c84a1f55f..b3641aeff27a 100644
> --- a/drivers/infiniband/hw/hns/hns_roce_hem.c
> +++ b/drivers/infiniband/hw/hns/hns_roce_hem.c
> @@ -326,7 +326,7 @@ static int hns_roce_set_hem(struct hns_roce_dev *hr_dev,
>  {
>  	spinlock_t *lock = &hr_dev->bt_cmd_lock;
>  	struct device *dev = hr_dev->dev;
> -	unsigned long end = 0;
> +	long end;
>  	unsigned long flags;
>  	struct hns_roce_hem_iter iter;
>  	void __iomem *bt_cmd;
> @@ -377,7 +377,7 @@ static int hns_roce_set_hem(struct hns_roce_dev *hr_dev,
>  		bt_cmd = hr_dev->reg_base + ROCEE_BT_CMD_H_REG;
>  
>  		end = HW_SYNC_TIMEOUT_MSECS;
> -		while (end) {
> +		while (end > 0) {
>  			if (!readl(bt_cmd) >> BT_CMD_SYNC_SHIFT)
>  				break;
>  
> diff --git a/drivers/infiniband/hw/hns/hns_roce_hw_v1.c b/drivers/infiniband/hw/hns/hns_roce_hw_v1.c
> index 1fc77b1f2c6d..e13fea71bcb8 100644
> --- a/drivers/infiniband/hw/hns/hns_roce_hw_v1.c
> +++ b/drivers/infiniband/hw/hns/hns_roce_hw_v1.c
> @@ -966,7 +966,7 @@ static int hns_roce_v1_recreate_lp_qp(struct hns_roce_dev *hr_dev)
>  	struct hns_roce_free_mr *free_mr;
>  	struct hns_roce_v1_priv *priv;
>  	struct completion comp;
> -	unsigned long end = HNS_ROCE_V1_RECREATE_LP_QP_TIMEOUT_MSECS;
> +	long end = HNS_ROCE_V1_RECREATE_LP_QP_TIMEOUT_MSECS;
>  
>  	priv = (struct hns_roce_v1_priv *)hr_dev->priv;
>  	free_mr = &priv->free_mr;
> @@ -986,7 +986,7 @@ static int hns_roce_v1_recreate_lp_qp(struct hns_roce_dev *hr_dev)
>  
>  	queue_work(free_mr->free_mr_wq, &(lp_qp_work->work));
>  
> -	while (end) {
> +	while (end > 0) {
>  		if (try_wait_for_completion(&comp))
>  			return 0;
>  		msleep(HNS_ROCE_V1_RECREATE_LP_QP_WAIT_VALUE);
> @@ -1104,7 +1104,7 @@ static int hns_roce_v1_dereg_mr(struct hns_roce_dev *hr_dev,
>  	struct hns_roce_free_mr *free_mr;
>  	struct hns_roce_v1_priv *priv;
>  	struct completion comp;
> -	unsigned long end = HNS_ROCE_V1_FREE_MR_TIMEOUT_MSECS;
> +	long end = HNS_ROCE_V1_FREE_MR_TIMEOUT_MSECS;
>  	unsigned long start = jiffies;
>  	int npages;
>  	int ret = 0;
> @@ -1134,7 +1134,7 @@ static int hns_roce_v1_dereg_mr(struct hns_roce_dev *hr_dev,
>  
>  	queue_work(free_mr->free_mr_wq, &(mr_work->work));
>  
> -	while (end) {
> +	while (end > 0) {
>  		if (try_wait_for_completion(&comp))
>  			goto free_mr;
>  		msleep(HNS_ROCE_V1_FREE_MR_WAIT_VALUE);
> @@ -2425,7 +2425,8 @@ static int hns_roce_v1_clear_hem(struct hns_roce_dev *hr_dev,
>  {
>  	struct device *dev = &hr_dev->pdev->dev;
>  	struct hns_roce_v1_priv *priv;
> -	unsigned long end = 0, flags = 0;
> +	unsigned long flags = 0;
> +	long end = HW_SYNC_TIMEOUT_MSECS;
>  	__le32 bt_cmd_val[2] = {0};
>  	void __iomem *bt_cmd;
>  	u64 bt_ba = 0;
> @@ -2463,7 +2464,6 @@ static int hns_roce_v1_clear_hem(struct hns_roce_dev *hr_dev,
>  
>  	bt_cmd = hr_dev->reg_base + ROCEE_BT_CMD_H_REG;
>  
> -	end = HW_SYNC_TIMEOUT_MSECS;
>  	while (1) {
>  		if (readl(bt_cmd) >> BT_CMD_SYNC_SHIFT) {
>  			if (end < 0) {

Good, thanks.