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GET /api/patches/815044/?format=api
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{
    "id": 815044,
    "url": "http://patchwork.ozlabs.org/api/patches/815044/?format=api",
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        "url": "http://patchwork.ozlabs.org/api/projects/46/?format=api",
        "name": "Intel Wired Ethernet development",
        "link_name": "intel-wired-lan",
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    "date": "2017-09-16T16:00:00",
    "name": "[net] driver: e1000: fix race condition between e1000_down() and e1000_watchdog",
    "commit_ref": null,
    "pull_url": null,
    "state": "accepted",
    "archived": false,
    "hash": "0cc2bdad001142b9c59fade43303148719fc2537",
    "submitter": {
        "id": 30369,
        "url": "http://patchwork.ozlabs.org/api/people/30369/?format=api",
        "name": "Vincenzo Maffione",
        "email": "v.maffione@gmail.com"
    },
    "delegate": {
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        "url": "http://patchwork.ozlabs.org/api/users/68/?format=api",
        "username": "jtkirshe",
        "first_name": "Jeff",
        "last_name": "Kirsher",
        "email": "jeffrey.t.kirsher@intel.com"
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    "mbox": "http://patchwork.ozlabs.org/project/intel-wired-lan/patch/20170916160000.3560-1-v.maffione@gmail.com/mbox/",
    "series": [
        {
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            "url": "http://patchwork.ozlabs.org/api/series/3684/?format=api",
            "web_url": "http://patchwork.ozlabs.org/project/intel-wired-lan/list/?series=3684",
            "date": "2017-09-16T16:00:00",
            "name": "[net] driver: e1000: fix race condition between e1000_down() and e1000_watchdog",
            "version": 1,
            "mbox": "http://patchwork.ozlabs.org/series/3684/mbox/"
        }
    ],
    "comments": "http://patchwork.ozlabs.org/api/patches/815044/comments/",
    "check": "pending",
    "checks": "http://patchwork.ozlabs.org/api/patches/815044/checks/",
    "tags": {},
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        "From": "Vincenzo Maffione <v.maffione@gmail.com>",
        "To": "jeffrey.t.kirsher@intel.com",
        "Date": "Sat, 16 Sep 2017 18:00:00 +0200",
        "Message-Id": "<20170916160000.3560-1-v.maffione@gmail.com>",
        "X-Mailer": "git-send-email 2.14.1",
        "X-Mailman-Approved-At": "Mon, 18 Sep 2017 17:07:45 +0000",
        "Cc": "netdev@vger.kernel.org, intel-wired-lan@lists.osuosl.org,\n\tlinux-kernel@vger.kernel.org, Vincenzo Maffione <v.maffione@gmail.com>",
        "Subject": "[Intel-wired-lan] [PATCH net] driver: e1000: fix race condition\n\tbetween e1000_down() and e1000_watchdog",
        "X-BeenThere": "intel-wired-lan@osuosl.org",
        "X-Mailman-Version": "2.1.18-1",
        "Precedence": "list",
        "List-Id": "Intel Wired Ethernet Linux Kernel Driver Development\n\t<intel-wired-lan.osuosl.org>",
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        "Errors-To": "intel-wired-lan-bounces@osuosl.org",
        "Sender": "\"Intel-wired-lan\" <intel-wired-lan-bounces@osuosl.org>"
    },
    "content": "This patch fixes a race condition that can result into the interface being\nup and carrier on, but with transmits disabled in the hardware.\nThe bug may show up by repeatedly IFF_DOWN+IFF_UP the interface, which\nallows e1000_watchdog() interleave with e1000_down().\n\n    CPU x                           CPU y\n    --------------------------------------------------------------------\n    e1000_down():\n        netif_carrier_off()\n                                    e1000_watchdog():\n                                        if (carrier == off) {\n                                            netif_carrier_on();\n                                            enable_hw_transmit();\n                                        }\n        disable_hw_transmit();\n                                    e1000_watchdog():\n                                        /* carrier on, do nothing */\n\nSigned-off-by: Vincenzo Maffione <v.maffione@gmail.com>\n---\n drivers/net/ethernet/intel/e1000/e1000_main.c | 11 +++++++++--\n 1 file changed, 9 insertions(+), 2 deletions(-)",
    "diff": "diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c\nindex 98375e1e1185..1982f7917a8d 100644\n--- a/drivers/net/ethernet/intel/e1000/e1000_main.c\n+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c\n@@ -520,8 +520,6 @@ void e1000_down(struct e1000_adapter *adapter)\n \tstruct net_device *netdev = adapter->netdev;\n \tu32 rctl, tctl;\n \n-\tnetif_carrier_off(netdev);\n-\n \t/* disable receives in the hardware */\n \trctl = er32(RCTL);\n \tew32(RCTL, rctl & ~E1000_RCTL_EN);\n@@ -537,6 +535,15 @@ void e1000_down(struct e1000_adapter *adapter)\n \tE1000_WRITE_FLUSH();\n \tmsleep(10);\n \n+\t/* Set the carrier off after transmits have been disabled in the\n+\t * hardware, to avoid race conditions with e1000_watchdog() (which\n+\t * may be running concurrently to us, checking for the carrier\n+\t * bit to decide whether it should enable transmits again). Such\n+\t * a race condition would result into transmission being disabled\n+\t * in the hardware until the next IFF_DOWN+IFF_UP cycle.\n+\t */\n+\tnetif_carrier_off(netdev);\n+\n \tnapi_disable(&adapter->napi);\n \n \te1000_irq_disable(adapter);\n",
    "prefixes": [
        "net"
    ]
}