[dpdk-dev] [PATCH] net/tap: fix unexpected link handler

[wangyunjian]

From: Yunjian Wang <wangyunj...@huawei.com>

The nic's interrupt source has some active handler, which maybe call
tap_dev_intr_handler() to set link handler. We should cancel the link
handler before close fd to prevent executing the link handler. It
triggers segfault.

Call Trace:
   0x00007f15e08dad99 in __rte_panic (Error adding fd %d epoll_ctl, %s\n")
   0x00007f15e08e9b87 in eal_intr_thread_main ()
   0x00007f15e249be15 in start_thread ()
   0x00007f15d5322f9d in clone ()

Fixes: c0bddd3a057f ("net/tap: add link status notification")
CC: sta...@dpdk.org

Signed-off-by: Yunjian Wang <wangyunj...@huawei.com>
---
 drivers/net/tap/rte_eth_tap.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
index 05470a211..6aa3d5cd3 100644
--- a/drivers/net/tap/rte_eth_tap.c
+++ b/drivers/net/tap/rte_eth_tap.c
@@ -18,6 +18,7 @@
 #include <rte_string_fns.h>
 #include <rte_ethdev.h>
 #include <rte_errno.h>
+#include <rte_cycles.h>
 
 #include <assert.h>
 #include <sys/types.h>
@@ -1563,13 +1564,12 @@ static int
 tap_lsc_intr_handle_set(struct rte_eth_dev *dev, int set)
 {
        struct pmd_internals *pmd = dev->data->dev_private;
+       int ret;
 
        /* In any case, disable interrupt if the conf is no longer there. */
        if (!dev->data->dev_conf.intr_conf.lsc) {
                if (pmd->intr_handle.fd != -1) {
-                       tap_nl_final(pmd->intr_handle.fd);
-                       rte_intr_callback_unregister(&pmd->intr_handle,
-                               tap_dev_intr_handler, dev);
+                       goto clean;
                }
                return 0;
        }
@@ -1580,9 +1580,26 @@ tap_lsc_intr_handle_set(struct rte_eth_dev *dev, int set)
                return rte_intr_callback_register(
                        &pmd->intr_handle, tap_dev_intr_handler, dev);
        }
+
+clean:
+       do {
+               ret = rte_intr_callback_unregister(&pmd->intr_handle,
+                       tap_dev_intr_handler, dev);
+               if (ret >= 0) {
+                       break;
+               } else if (ret == -EAGAIN) {
+                       rte_delay_ms(100);
+               } else {
+                       TAP_LOG(ERR, "intr callback unregister failed: %d",
+                                    ret);
+                       break;
+               }
+       } while (true);
+
        tap_nl_final(pmd->intr_handle.fd);
-       return rte_intr_callback_unregister(&pmd->intr_handle,
-                                           tap_dev_intr_handler, dev);
+       pmd->intr_handle.fd = -1;
+
+       return 0;
 }
 
 static int
-- 
2.19.1