linux-kernel - Re: [PATCH v2 06/15] NTB: ntb_perf: Add full multi-port NTB API support

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Date:   Wed, 6 Dec 2017 09:17:37 +0800
From:   kbuild test robot <lkp@...el.com>
To:     Serge Semin <fancer.lancer@...il.com>
Cc:     kbuild-all@...org, jdmason@...zu.us, dave.jiang@...el.com,
        Allen.Hubbe@....com, Shyam-sundar.S-k@....com,
        Xiangliang.Yu@....com, gary.hook@....com,
        Sergey.Semin@...latforms.ru, linux-ntb@...glegroups.com,
        linux-kernel@...r.kernel.org, Serge Semin <fancer.lancer@...il.com>
Subject: Re: [PATCH v2 06/15] NTB: ntb_perf: Add full multi-port NTB API
 support

Hi Serge,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v4.15-rc2]
[cannot apply to ntb/ntb-next next-20171205]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Serge-Semin/NTB-Add-full-multi-port-API-support-to-the-test-drivers/20171206-081300
config: x86_64-randconfig-x004-201749 (attached as .config)
compiler: gcc-7 (Debian 7.2.0-12) 7.2.1 20171025
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   drivers/ntb/test/ntb_perf.c: In function 'perf_thread_work':
>> drivers/ntb/test/ntb_perf.c:821:22: warning: 'try' may be used uninitialized in this function [-Wmaybe-uninitialized]
     } while (!tx && (try++ < DMA_TRIES));
                      ~~~^~
   drivers/ntb/test/ntb_perf.c:782:6: note: 'try' was declared here
     int try, ret = 0;
         ^~~

vim +/try +821 drivers/ntb/test/ntb_perf.c

   775	
   776	static int perf_copy_chunk(struct perf_thread *pthr,
   777				   void __iomem *dst, void *src, size_t len)
   778	{
   779		struct dma_async_tx_descriptor *tx;
   780		struct dmaengine_unmap_data *unmap;
   781		struct device *dma_dev;
   782		int try, ret = 0;
   783	
   784		if (!use_dma) {
   785			memcpy_toio(dst, src, len);
   786			goto ret_check_tsync;
   787		}
   788	
   789		dma_dev = pthr->dma_chan->device->dev;
   790	
   791		if (!is_dma_copy_aligned(pthr->dma_chan->device, offset_in_page(src),
   792					 offset_in_page(dst), len))
   793			return -EIO;
   794	
   795		unmap = dmaengine_get_unmap_data(dma_dev, 2, GFP_NOWAIT);
   796		if (!unmap)
   797			return -ENOMEM;
   798	
   799		unmap->len = len;
   800		unmap->addr[0] = dma_map_page(dma_dev, virt_to_page(src),
   801			offset_in_page(src), len, DMA_TO_DEVICE);
   802		if (dma_mapping_error(dma_dev, unmap->addr[0])) {
   803			ret = -EIO;
   804			goto err_free_resource;
   805		}
   806		unmap->to_cnt = 1;
   807	
   808		unmap->addr[1] = dma_map_page(dma_dev, virt_to_page(dst),
   809			offset_in_page(dst), len, DMA_FROM_DEVICE);
   810		if (dma_mapping_error(dma_dev, unmap->addr[1])) {
   811			ret = -EIO;
   812			goto err_free_resource;
   813		}
   814		unmap->from_cnt = 1;
   815	
   816		do {
   817			tx = dmaengine_prep_dma_memcpy(pthr->dma_chan, unmap->addr[1],
   818				unmap->addr[0], len, DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
   819			if (!tx)
   820				msleep(DMA_MDELAY);
 > 821		} while (!tx && (try++ < DMA_TRIES));
   822	
   823		if (!tx) {
   824			ret = -EIO;
   825			goto err_free_resource;
   826		}
   827	
   828		tx->callback = perf_dma_copy_callback;
   829		tx->callback_param = pthr;
   830		dma_set_unmap(tx, unmap);
   831	
   832		if (dma_submit_error(dmaengine_submit(tx))) {
   833			dmaengine_unmap_put(unmap);
   834			goto err_free_resource;
   835		}
   836	
   837		dmaengine_unmap_put(unmap);
   838	
   839		atomic_inc(&pthr->dma_sync);
   840		dma_async_issue_pending(pthr->dma_chan);
   841	
   842	ret_check_tsync:
   843		return likely(atomic_read(&pthr->perf->tsync) > 0) ? 0 : -EINTR;
   844	
   845	err_free_resource:
   846		dmaengine_unmap_put(unmap);
   847	
   848		return ret;
   849	}
   850	

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