[dpdk-dev] [PATCH 2/3] devargs: delay freeing previous devargs when overriding them

[Darek Stojaczyk <dariusz.stojaczyk@intel.com>]

In eal hotplug path, the previous devargs may be still
referenced by device structs at the time the rte_devargs_insert()
is called. Those references are updated almost immediately
afterwards, but in cases something goes wrong and they cannot
be updated, we might want to still keep the old devargs around.

This patch modifies rte_devargs_insert() so that it returns
a pointer to previous devargs that are being overridden. In
case something in the EAL hotplug path goes wrong, we can now
remove the newly inserted devargs and re-insert the old ones.

Note: Functional changes will come in a subsequent patch. This
      one only extends the API.

Signed-off-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
---
 drivers/bus/vdev/vdev.c                     | 12 +++++++++---
 lib/librte_eal/common/eal_common_dev.c      | 11 +++++++----
 lib/librte_eal/common/eal_common_devargs.c  | 21 ++++++++++++++-------
 lib/librte_eal/common/include/rte_devargs.h |  8 ++------
 4 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/drivers/bus/vdev/vdev.c b/drivers/bus/vdev/vdev.c
index 9c66bdc78..bbdae2314 100644
--- a/drivers/bus/vdev/vdev.c
+++ b/drivers/bus/vdev/vdev.c
@@ -9,6 +9,7 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include <sys/queue.h>
+#include <assert.h>
 
 #include <rte_eal.h>
 #include <rte_dev.h>
@@ -207,7 +208,7 @@ insert_vdev(const char *name, const char *args,
 		bool init)
 {
 	struct rte_vdev_device *dev;
-	struct rte_devargs *devargs;
+	struct rte_devargs *devargs, *prev_devargs;
 	int ret;
 
 	if (name == NULL)
@@ -239,8 +240,13 @@ insert_vdev(const char *name, const char *args,
 	}
 
 	TAILQ_INSERT_TAIL(&vdev_device_list, dev, next);
-	if (init)
-		rte_devargs_insert(devargs);
+	if (init) {
+		rte_devargs_insert(devargs, &prev_devargs);
+		 /* any previous devargs should have been caught by the above
+		  * find_vdev(name) check
+		  */
+		assert(prev_devargs == NULL);
+	}
 
 	if (p_dev)
 		*p_dev = dev;
diff --git a/lib/librte_eal/common/eal_common_dev.c b/lib/librte_eal/common/eal_common_dev.c
index 62e9ed477..4cb424df1 100644
--- a/lib/librte_eal/common/eal_common_dev.c
+++ b/lib/librte_eal/common/eal_common_dev.c
@@ -131,7 +131,7 @@ int
 local_dev_probe(const char *devargs, struct rte_device **new_dev)
 {
 	struct rte_device *dev;
-	struct rte_devargs *da;
+	struct rte_devargs *da, *prev_da;
 	int ret;
 
 	*new_dev = NULL;
@@ -150,9 +150,12 @@ local_dev_probe(const char *devargs, struct rte_device **new_dev)
 		goto err_devarg;
 	}
 
-	ret = rte_devargs_insert(da);
-	if (ret)
-		goto err_devarg;
+	rte_devargs_insert(da, &prev_da);
+
+	if (prev_da != NULL) {
+		free(prev_da->args);
+		free(prev_da);
+	}
 
 	ret = da->bus->scan();
 	if (ret)
diff --git a/lib/librte_eal/common/eal_common_devargs.c b/lib/librte_eal/common/eal_common_devargs.c
index b7b9cb69e..c46365b69 100644
--- a/lib/librte_eal/common/eal_common_devargs.c
+++ b/lib/librte_eal/common/eal_common_devargs.c
@@ -262,16 +262,23 @@ rte_devargs_parsef(struct rte_devargs *da, const char *format, ...)
 	return ret;
 }
 
-int __rte_experimental
-rte_devargs_insert(struct rte_devargs *da)
+void __rte_experimental
+rte_devargs_insert(struct rte_devargs *da, struct rte_devargs **prev_da)
 {
-	int ret;
+	struct rte_devargs *d;
+	void *tmp;
+
+	*prev_da = NULL;
+	TAILQ_FOREACH_SAFE(d, &devargs_list, next, tmp) {
+		if (strcmp(d->bus->name, da->bus->name) == 0 &&
+		    strcmp(d->name, da->name) == 0) {
+			TAILQ_REMOVE(&devargs_list, d, next);
+			*prev_da = d;
+			break;
+		}
+	}
 
-	ret = rte_devargs_remove(da);
-	if (ret < 0)
-		return ret;
 	TAILQ_INSERT_TAIL(&devargs_list, da, next);
-	return 0;
 }
 
 /* store a whitelist parameter for later parsing */
diff --git a/lib/librte_eal/common/include/rte_devargs.h b/lib/librte_eal/common/include/rte_devargs.h
index b1f121f83..753cf7f54 100644
--- a/lib/librte_eal/common/include/rte_devargs.h
+++ b/lib/librte_eal/common/include/rte_devargs.h
@@ -146,14 +146,10 @@ __attribute__((format(printf, 2, 0)));
  *
  * @param da
  *  The devargs structure to insert.
- *
- * @return
- *   - 0 on success
- *   - Negative on error.
  */
 __rte_experimental
-int
-rte_devargs_insert(struct rte_devargs *da);
+void
+rte_devargs_insert(struct rte_devargs *da, struct rte_devargs **prev_da);
 
 /**
  * Add a device to the user device list
-- 
2.17.1