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Subject[PATCH] avr32: fix deadlock when reading clock list in debugfs
From: Ole Henrik Jahren <olehenja@alumni.ntnu.no>

clk_show() already has clk_list_lock. Make a version of clk_get(),
clk_get_locked(), that does not attempt to take the lock a second time.

Signed-off-by: Ole Henrik Jahren <olehenja@alumni.ntnu.no>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
---
arch/avr32/mach-at32ap/clock.c | 27 ++++++++++++++++++++-------
1 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/arch/avr32/mach-at32ap/clock.c b/arch/avr32/mach-at32ap/clock.c
index 442f08c..3951993 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, int locked)
{
struct clk *clk;

- spin_lock(&clk_list_lock);
+ if (!locked)
+ 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);
+ if (!locked)
+ spin_unlock(&clk_list_lock);
return clk;
}
}

- spin_unlock(&clk_list_lock);
+ if (!locked)
+ spin_unlock(&clk_list_lock);
return ERR_PTR(-ENOENT);
}
+
+struct clk *clk_get(struct device *dev, const char *id)
+{
+ return __clk_get(dev, id, 0);
+}
EXPORT_SYMBOL(clk_get);

void clk_put(struct clk *clk)
@@ -227,6 +235,11 @@ dump_clock(struct clk *parent, struct clkinf *r)
r->nest = nest;
}

+static struct clk *clk_get_locked(struct device *dev, const char *id)
+{
+ return __clk_get(dev, id, 1);
+}
+
static int clk_show(struct seq_file *s, void *unused)
{
struct clkinf r;
@@ -257,15 +270,15 @@ 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_locked(NULL, "osc32k");
dump_clock(clk, &r);
clk_put(clk);

- clk = clk_get(NULL, "osc0");
+ clk = clk_get_locked(NULL, "osc0");
dump_clock(clk, &r);
clk_put(clk);

- clk = clk_get(NULL, "osc1");
+ clk = clk_get_locked(NULL, "osc1");
dump_clock(clk, &r);
clk_put(clk);

--
1.7.2.2


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