From: Amir Shehata <amir.shehata@intel.com>
Date: Wed, 17 Dec 2014 17:35:15 +0000 (-0800)
Subject: LU-6010 lnet: prevent assert on LNet module unload
X-Git-Tag: 2.6.94~4
X-Git-Url: https://git.whamcloud.com/?p=fs%2Flustre-release.git;a=commitdiff_plain;h=refs%2Fchanges%2F10%2F13110%2F16;hp=f3e49e66608a20ac1b006b5e4202ad8ad88c1979

LU-6010 lnet: prevent assert on LNet module unload

There is a use case where lnet can be unloaded while there are
no NIs configured.  Removing lnet in this case will cause
LNetFini() to be called without a prior call to LNetNIFini().
This will cause the LASSERT(the_lnet.ln_refcount == 0) to be
triggered.

To deal with this use case when LNet is configured a reference
count on the module is taken using try_module_get().  This way
LNet must be unconfigured before it could be removed; therefore
avoiding the above case.  When LNet is unconfigured module_put()
is called to return the reference count.

Signed-off-by: Amir Shehata <amir.shehata@intel.com>
Change-Id: I0f283eeb395fa9a076a4d65ab3edd5e7807fc169
Reviewed-on: http://review.whamcloud.com/13110
Tested-by: Jenkins
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
---

diff --git a/lnet/lnet/module.c b/lnet/lnet/module.c
index 197ff25..a8f39b3 100644
--- a/lnet/lnet/module.c
+++ b/lnet/lnet/module.c
@@ -53,13 +53,21 @@ lnet_configure(void *arg)
 	LNET_MUTEX_LOCK(&lnet_config_mutex);
 
 	if (!the_lnet.ln_niinit_self) {
+		rc = try_module_get(THIS_MODULE);
+
+		if (rc != 1)
+			goto out;
+
 		rc = LNetNIInit(LNET_PID_LUSTRE);
 		if (rc >= 0) {
 			the_lnet.ln_niinit_self = 1;
 			rc = 0;
+		} else {
+			module_put(THIS_MODULE);
 		}
 	}
 
+out:
 	LNET_MUTEX_UNLOCK(&lnet_config_mutex);
 	return rc;
 }
@@ -67,21 +75,23 @@ lnet_configure(void *arg)
 static int
 lnet_unconfigure (void)
 {
-        int   refcount;
+	int   refcount;
+
+	LNET_MUTEX_LOCK(&lnet_config_mutex);
 
-        LNET_MUTEX_LOCK(&lnet_config_mutex);
+	if (the_lnet.ln_niinit_self) {
+		the_lnet.ln_niinit_self = 0;
+		LNetNIFini();
+		module_put(THIS_MODULE);
+	}
 
-        if (the_lnet.ln_niinit_self) {
-                the_lnet.ln_niinit_self = 0;
-                LNetNIFini();
-        }
+	LNET_MUTEX_LOCK(&the_lnet.ln_api_mutex);
+	refcount = the_lnet.ln_refcount;
+	LNET_MUTEX_UNLOCK(&the_lnet.ln_api_mutex);
 
-        LNET_MUTEX_LOCK(&the_lnet.ln_api_mutex);
-        refcount = the_lnet.ln_refcount;
-        LNET_MUTEX_UNLOCK(&the_lnet.ln_api_mutex);
+	LNET_MUTEX_UNLOCK(&lnet_config_mutex);
 
-        LNET_MUTEX_UNLOCK(&lnet_config_mutex);
-        return (refcount == 0) ? 0 : -EBUSY;
+	return (refcount == 0) ? 0 : -EBUSY;
 }
 
 static int