[PATCH v2] um: net: replace GFP_KERNEL with GFP_ATOMIC when spinlock is held

[Saurabh Sengar]

replace GFP_KERNEL with GFP_ATOMIC while spinlock is held,
as code while holding a spinlock should be atomic.
GFP_KERNEL may sleep and can cause deadlock,
where as GFP_ATOMIC may fail but certainly avoids deadlock

Signed-off-by: Saurabh Sengar <saurabh.tr...@gmail.com>
---
v2: correcting the subject

 arch/um/drivers/net_kern.c | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c
index f70dd54..7d4b709 100644
--- a/arch/um/drivers/net_kern.c
+++ b/arch/um/drivers/net_kern.c
@@ -388,16 +388,22 @@ static const struct net_device_ops uml_netdev_ops = {
 static int driver_registered;
 
 static void eth_configure(int n, void *init, char *mac,
-                         struct transport *transport)
+                         struct transport *transport, bool atomic)
 {
        struct uml_net *device;
        struct net_device *dev;
        struct uml_net_private *lp;
        int err, size;
+       int gfp_mask;
 
        size = transport->private_size + sizeof(struct uml_net_private);
 
-       device = kzalloc(sizeof(*device), GFP_KERNEL);
+       if (atomic)
+               gfp_mask = GFP_ATOMIC;
+       else
+               gfp_mask = GFP_KERNEL;
+
+       device = kzalloc(sizeof(*device), gfp_mask);
        if (device == NULL) {
                printk(KERN_ERR "eth_configure failed to allocate struct "
                       "uml_net\n");
@@ -568,9 +574,10 @@ static LIST_HEAD(transports);
 static LIST_HEAD(eth_cmd_line);
 
 static int check_transport(struct transport *transport, char *eth, int n,
-                          void **init_out, char **mac_out)
+                          void **init_out, char **mac_out, bool atomic)
 {
        int len;
+       int gfp_mask;
 
        len = strlen(transport->name);
        if (strncmp(eth, transport->name, len))
@@ -582,7 +589,12 @@ static int check_transport(struct transport *transport, 
char *eth, int n,
        else if (*eth != '\0')
                return 0;
 
-       *init_out = kmalloc(transport->setup_size, GFP_KERNEL);
+       if (atomic)
+               gfp_mask = GFP_ATOMIC;
+       else
+               gfp_mask = GFP_KERNEL;
+
+       *init_out = kmalloc(transport->setup_size, gfp_mask);
        if (*init_out == NULL)
                return 1;
 
@@ -600,6 +612,7 @@ void register_transport(struct transport *new)
        void *init;
        char *mac = NULL;
        int match;
+       bool atomic = false;
 
        spin_lock(&transports_lock);
        BUG_ON(!list_empty(&new->list));
@@ -609,11 +622,11 @@ void register_transport(struct transport *new)
        list_for_each_safe(ele, next, &eth_cmd_line) {
                eth = list_entry(ele, struct eth_init, list);
                match = check_transport(new, eth->init, eth->index, &init,
-                                       &mac);
+                                       &mac, atomic);
                if (!match)
                        continue;
                else if (init != NULL) {
-                       eth_configure(eth->index, init, mac, new);
+                       eth_configure(eth->index, init, mac, new, atomic);
                        kfree(init);
                }
                list_del(&eth->list);
@@ -627,14 +640,16 @@ static int eth_setup_common(char *str, int index)
        void *init;
        char *mac = NULL;
        int found = 0;
+       bool atomic = false;
 
        spin_lock(&transports_lock);
+       atomic = true;
        list_for_each(ele, &transports) {
                transport = list_entry(ele, struct transport, list);
-               if (!check_transport(transport, str, index, &init, &mac))
+               if (!check_transport(transport, str, index, &init, &mac, 
atomic))
                        continue;
                if (init != NULL) {
-                       eth_configure(index, init, mac, transport);
+                       eth_configure(index, init, mac, transport, atomic);
                        kfree(init);
                }
                found = 1;
-- 
1.9.1

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