Commit d6838a62 authored Sep 18, 2012 by Tushar Behera Committed by Kukjin Kim Sep 18, 2012

ARM: SAMSUNG: Use spin_lock_{irqsave,irqrestore} in clk_set_rate



The spinlock clocks_lock can be held during ISR, hence it is not safe to
hold that lock with disabling interrupts.

It fixes following potential deadlock.

=========================================================
[ INFO: possible irq lock inversion dependency detected ]
3.6.0-rc4+ #2 Not tainted
---------------------------------------------------------
swapper/0/1 just changed the state of lock:
 (&(&host->lock)->rlock){-.....}, at: [<c027fb0d>] sdhci_irq+0x15/0x564
but this lock took another, HARDIRQ-unsafe lock in the past:
 (clocks_lock){+.+...}

and interrupts could create inverse lock ordering between them.

other info that might help us debug this:
 Possible interrupt unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(clocks_lock);
                               local_irq_disable();
                               lock(&(&host->lock)->rlock);
                               lock(clocks_lock);
  <Interrupt>
    lock(&(&host->lock)->rlock);

 *** DEADLOCK ***

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

parent dbc5e1e8

arch/arm/plat-samsung/clock.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -144,6 +144,7 @@ long clk_round_rate(struct clk *clk, unsigned long rate)

		int clk_set_rate(struct clk *clk, unsigned long rate)
		{
		unsigned long flags;
		int ret;

		if (IS_ERR(clk))
		@@ -159,9 +160,9 @@ int clk_set_rate(struct clk *clk, unsigned long rate)
		if (clk->ops == NULL \|\| clk->ops->set_rate == NULL)
		return -EINVAL;

		spin_lock(&clocks_lock);
		spin_lock_irqsave(&clocks_lock, flags);
		ret = (clk->ops->set_rate)(clk, rate);
		spin_unlock(&clocks_lock);
		spin_unlock_irqrestore(&clocks_lock, flags);

		return ret;
		}