avr32: fix deadlock when reading clock list in debugfs

When writing out /sys/kernel/debug/at32ap_clk, clock list lock is being
held while clk_get() is called. clk_get() attempts to take the same
lock, which results in deadlock. Introduce and call lock free version,
__clk_get(), instead.

Signed-off-by: Ole Henrik Jahren <olehenja@alumni.ntnu.no>
Cc: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
Signed-off-by: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>

1 files changed, 16 insertions, 8 deletions

diff --git a/arch/avr32/mach-at32ap/clock.c b/arch/avr32/mach-at32ap/clock.c
index 442f08c5e641..86925fd6ea5b 100644
--- a/arch/avr32/mach-at32ap/clock.c
+++ b/arch/avr32/mach-at32ap/clock.c
@@ -35,22 +35,30 @@ void at32_clk_register(struct clk *clk)
         spin_unlock(&clk_list_lock);
 }
 
-struct clk *clk_get(struct device *dev, const char *id)
+static struct clk *__clk_get(struct device *dev, const char *id)
 {
         struct clk *clk;
 
-        spin_lock(&clk_list_lock);
-
         list_for_each_entry(clk, &at32_clock_list, list) {
                 if (clk->dev == dev && strcmp(id, clk->name) == 0) {
-                        spin_unlock(&clk_list_lock);
                         return clk;
                 }
         }
 
-        spin_unlock(&clk_list_lock);
         return ERR_PTR(-ENOENT);
 }
+
+struct clk *clk_get(struct device *dev, const char *id)
+{
+        struct clk *clk;
+
+        spin_lock(&clk_list_lock);
+        clk = __clk_get(dev, id);
+        spin_unlock(&clk_list_lock);
+
+        return clk;
+}
+
 EXPORT_SYMBOL(clk_get);
 
 void clk_put(struct clk *clk)
@@ -257,15 +265,15 @@ static int clk_show(struct seq_file *s, void *unused)
         spin_lock(&clk_list_lock);
 
         /* show clock tree as derived from the three oscillators */
-        clk = clk_get(NULL, "osc32k");
+        clk = __clk_get(NULL, "osc32k");
         dump_clock(clk, &r);
         clk_put(clk);
 
-        clk = clk_get(NULL, "osc0");
+        clk = __clk_get(NULL, "osc0");
         dump_clock(clk, &r);
         clk_put(clk);
 
-        clk = clk_get(NULL, "osc1");
+        clk = __clk_get(NULL, "osc1");
         dump_clock(clk, &r);
         clk_put(clk);