[PATCH 2/2] ehea: fix possible DLPAR/mem deadlock

[Thomas Klein]

Force serialization of userspace-triggered DLPAR/mem operations

Signed-off-by: Thomas Klein <tkl...@de.ibm.com>
---

Patch created against 2.6.34-rc4

diff -Nurp linux-2.6.34-rc4.orig//drivers/net/ehea/ehea.h 
linux-2.6.34-rc4//drivers/net/ehea/ehea.h
--- linux-2.6.34-rc4.orig//drivers/net/ehea/ehea.h      2010-04-19 
11:54:07.000000000 +0200
+++ linux-2.6.34-rc4//drivers/net/ehea/ehea.h   2010-04-19 12:00:14.000000000 
+0200
@@ -40,7 +40,7 @@
 #include <asm/io.h>

 #define DRV_NAME       "ehea"
-#define DRV_VERSION    "EHEA_0102"
+#define DRV_VERSION    "EHEA_0103"

 /* eHEA capability flags */
 #define DLPAR_PORT_ADD_REM 1
diff -Nurp linux-2.6.34-rc4.orig//drivers/net/ehea/ehea_main.c 
linux-2.6.34-rc4//drivers/net/ehea/ehea_main.c
--- linux-2.6.34-rc4.orig//drivers/net/ehea/ehea_main.c 2010-04-19 
11:59:11.000000000 +0200
+++ linux-2.6.34-rc4//drivers/net/ehea/ehea_main.c      2010-04-19 
11:59:50.000000000 +0200
@@ -2889,7 +2889,6 @@ static void ehea_rereg_mrs(struct work_s
        int ret, i;
        struct ehea_adapter *adapter;

-       mutex_lock(&dlpar_mem_lock);
        ehea_info("LPAR memory changed - re-initializing driver");

        list_for_each_entry(adapter, &adapter_list, list)
@@ -2959,7 +2958,6 @@ static void ehea_rereg_mrs(struct work_s
                }
        ehea_info("re-initializing driver complete");
 out:
-       mutex_unlock(&dlpar_mem_lock);
        return;
 }

@@ -3542,7 +3540,14 @@ void ehea_crash_handler(void)
 static int ehea_mem_notifier(struct notifier_block *nb,
                              unsigned long action, void *data)
 {
+       int ret = NOTIFY_BAD;
        struct memory_notify *arg = data;
+
+       if (!mutex_trylock(&dlpar_mem_lock)) {
+               ehea_info("ehea_mem_notifier must not be called parallelized");
+               goto out;
+       }
+
        switch (action) {
        case MEM_CANCEL_OFFLINE:
                ehea_info("memory offlining canceled");
@@ -3551,14 +3556,14 @@ static int ehea_mem_notifier(struct noti
                ehea_info("memory is going online");
                set_bit(__EHEA_STOP_XFER, &ehea_driver_flags);
                if (ehea_add_sect_bmap(arg->start_pfn, arg->nr_pages))
-                       return NOTIFY_BAD;
+                       goto out_unlock;
                ehea_rereg_mrs(NULL);
                break;
        case MEM_GOING_OFFLINE:
                ehea_info("memory is going offline");
                set_bit(__EHEA_STOP_XFER, &ehea_driver_flags);
                if (ehea_rem_sect_bmap(arg->start_pfn, arg->nr_pages))
-                       return NOTIFY_BAD;
+                       goto out_unlock;
                ehea_rereg_mrs(NULL);
                break;
        default:
@@ -3566,8 +3571,12 @@ static int ehea_mem_notifier(struct noti
        }

        ehea_update_firmware_handles();
+       ret = NOTIFY_OK;

-       return NOTIFY_OK;
+out_unlock:
+       mutex_unlock(&dlpar_mem_lock);
+out:
+       return ret;
 }

 static struct notifier_block ehea_mem_nb = {
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