From: Nishanth Menon Date: Thu, 15 Mar 2012 18:24:31 +0000 (-0500) Subject: ARM: OMAP: clock: fix race in disable all clocks X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=0eb4fd9b3e4d08973f7f086dbdb14a0ad5c3d76d;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git ARM: OMAP: clock: fix race in disable all clocks clk_disable_unused is invoked when CONFIG_OMAP_RESET_CLOCKS=y. Since clk_disable_unused is called as lateinitcall, there can be more than a few workqueues executing off secondary CPU(s). The current code does the following: a) checks if clk is unused b) holds lock c) disables clk d) unlocks Between (a) and (b) being executed on CPU0, It is possible to have a driver executing on CPU1 which could do a get_sync->clk_get (and increase the use_count) of the clock which was just about to be disabled by clk_disable_unused. We ensure instead that the entire list traversal is protected by the lock allowing for parent child clock traversal which could be potentially be done by runtime operations to be safe as well. Reported-by: Todd Poynor Signed-off-by: Nishanth Menon Signed-off-by: Paul Walmsley --- diff --git a/arch/arm/plat-omap/clock.c b/arch/arm/plat-omap/clock.c index 56b6f8b7053e..8506cbb7fea4 100644 --- a/arch/arm/plat-omap/clock.c +++ b/arch/arm/plat-omap/clock.c @@ -441,6 +441,8 @@ static int __init clk_disable_unused(void) return 0; pr_info("clock: disabling unused clocks to save power\n"); + + spin_lock_irqsave(&clockfw_lock, flags); list_for_each_entry(ck, &clocks, node) { if (ck->ops == &clkops_null) continue; @@ -448,10 +450,9 @@ static int __init clk_disable_unused(void) if (ck->usecount > 0 || !ck->enable_reg) continue; - spin_lock_irqsave(&clockfw_lock, flags); arch_clock->clk_disable_unused(ck); - spin_unlock_irqrestore(&clockfw_lock, flags); } + spin_unlock_irqrestore(&clockfw_lock, flags); return 0; }