powerpc/pseries: Correct rtas_data_buf locking in dlpar code

The dlpar code can cause a deadlock to occur when making the RTAS
configure-connector call.  This occurs because we make kmalloc calls,
which can block, while parsing the rtas_data_buf and holding the
rtas_data_buf_lock.  This an cause issues if someone else attempts
to grab the rtas_data_bug_lock.

This patch alleviates this issue by copying the contents of the rtas_data_buf
to a local buffer before parsing.  This allows us to only hold the
rtas_data_buf_lock around the RTAS configure-connector calls.

Signed-off-by: Nathan Fontenot <nfont@austin.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/platforms/pseries/dlpar.c b/arch/powerpc/platforms/pseries/dlpar.c
index 227c1c3..72d8054 100644 (file)
--- a/arch/powerpc/platforms/pseries/dlpar.c
+++ b/arch/powerpc/platforms/pseries/dlpar.c
@@ -129,20 +129,35 @@ struct device_node *dlpar_configure_connector(u32 drc_index)
        struct property *property;
        struct property *last_property = NULL;
        struct cc_workarea *ccwa;
+       char *data_buf;
        int cc_token;
-       int rc;
+       int rc = -1;
 
        cc_token = rtas_token("ibm,configure-connector");
        if (cc_token == RTAS_UNKNOWN_SERVICE)
                return NULL;
 
-       spin_lock(&rtas_data_buf_lock);
-       ccwa = (struct cc_workarea *)&rtas_data_buf[0];
+       data_buf = kzalloc(RTAS_DATA_BUF_SIZE, GFP_KERNEL);
+       if (!data_buf)
+               return NULL;
+
+       ccwa = (struct cc_workarea *)&data_buf[0];
        ccwa->drc_index = drc_index;
        ccwa->zero = 0;
 
-       rc = rtas_call(cc_token, 2, 1, NULL, rtas_data_buf, NULL);
-       while (rc) {
+       do {
+               /* Since we release the rtas_data_buf lock between configure
+                * connector calls we want to re-populate the rtas_data_buffer
+                * with the contents of the previous call.
+                */
+               spin_lock(&rtas_data_buf_lock);
+
+               memcpy(rtas_data_buf, data_buf, RTAS_DATA_BUF_SIZE);
+               rc = rtas_call(cc_token, 2, 1, NULL, rtas_data_buf, NULL);
+               memcpy(data_buf, rtas_data_buf, RTAS_DATA_BUF_SIZE);
+
+               spin_unlock(&rtas_data_buf_lock);
+
                switch (rc) {
                case NEXT_SIBLING:
                        dn = dlpar_parse_cc_node(ccwa);
@@ -197,18 +212,19 @@ struct device_node *dlpar_configure_connector(u32 drc_index)
                               "returned from configure-connector\n", rc);
                        goto cc_error;
                }
+       } while (rc);
 
-               rc = rtas_call(cc_token, 2, 1, NULL, rtas_data_buf, NULL);
+cc_error:
+       kfree(data_buf);
+
+       if (rc) {
+               if (first_dn)
+                       dlpar_free_cc_nodes(first_dn);
+
+               return NULL;
        }
 
-       spin_unlock(&rtas_data_buf_lock);
        return first_dn;
-
-cc_error:
-       if (first_dn)
-               dlpar_free_cc_nodes(first_dn);
-       spin_unlock(&rtas_data_buf_lock);
-       return NULL;
 }
 
 static struct device_node *derive_parent(const char *path)