From c1dcc927dae01dfd4904ee82ce2c00b50eab6dc3 Mon Sep 17 00:00:00 2001 From: Soren Brinkmann Date: Tue, 26 Nov 2013 17:04:50 -0800 Subject: [PATCH] clocksource: cadence_ttc: Fix mutex taken inside interrupt context When the kernel is compiled with: CONFIG_HIGH_RES_TIMERS=no CONFIG_HZ_PERIODIC=yes CONFIG_DEBUG_ATOMIC_SLEEP=yes The following WARN appears: WARNING: CPU: 1 PID: 0 at linux/kernel/mutex.c:856 mutex_trylock+0x70/0x1fc() DEBUG_LOCKS_WARN_ON(in_interrupt()) Modules linked in: CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.12.0-xilinx-dirty #93 [] (unwind_backtrace+0x0/0x11c) from [] (show_stack+0x10/0x14) [] (show_stack+0x10/0x14) from [] (dump_stack+0x7c/0xc0) [] (dump_stack+0x7c/0xc0) from [] (warn_slowpath_common+0x60/0x84) [] (warn_slowpath_common+0x60/0x84) from [] (warn_slowpath_fmt+0x2c/0x3c) [] (warn_slowpath_fmt+0x2c/0x3c) from [] (mutex_trylock+0x70/0x1fc) [] (mutex_trylock+0x70/0x1fc) from [] (clk_prepare_lock+0xc/0xe4) [] (clk_prepare_lock+0xc/0xe4) from [] (clk_get_rate+0xc/0x44) [] (clk_get_rate+0xc/0x44) from [] (ttc_set_mode+0x34/0x78) [] (ttc_set_mode+0x34/0x78) from [] (clockevents_set_mode+0x28/0x5c) [] (clockevents_set_mode+0x28/0x5c) from [] (tick_broadcast_on_off+0x190/0x1c0) [] (tick_broadcast_on_off+0x190/0x1c0) from [] (clockevents_notify+0x58/0x1ac) [] (clockevents_notify+0x58/0x1ac) from [] (cpuidle_setup_broadcast_timer+0x20/0x24) [] (cpuidle_setup_broadcast_timer+0x20/0x24) from [] (generic_smp_call_function_single_interrupt+0) [] (generic_smp_call_function_single_interrupt+0xe0/0x130) from [] (handle_IPI+0x88/0x118) [] (handle_IPI+0x88/0x118) from [] (gic_handle_irq+0x58/0x60) [] (gic_handle_irq+0x58/0x60) from [] (__irq_svc+0x44/0x78) Exception stack(0xef099fa0 to 0xef099fe8) 9fa0: 00000001 ef092100 00000000 ef092100 ef098000 00000015 c0399f2c c0579d74 9fc0: 0000406a 413fc090 00000000 00000000 00000000 ef099fe8 c00666ec c000f46c 9fe0: 20000113 ffffffff [] (__irq_svc+0x44/0x78) from [] (arch_cpu_idle+0x34/0x3c) [] (arch_cpu_idle+0x34/0x3c) from [] (cpu_startup_entry+0xa8/0x10c) [] (cpu_startup_entry+0xa8/0x10c) from [<000085a4>] (0x85a4) We are in an interrupt context (IPI) and we are calling clk_get_rate in the set_mode function which in turn ends up by getting a mutex... Even if that does not hang, it is a potential kernel deadlock. It is not allowed to call clk_get_rate() from interrupt context. To avoid such calls the timer input frequency is stored in the driver's data struct which makes it accessible to the driver in any context. [dlezcano] completed the changelog with the WARN trace and added a more detailed description. Tested on zync zc702. Acked-by: Daniel Lezcano Tested-by: Daniel Lezcano Signed-off-by: Soren Brinkmann Signed-off-by: Daniel Lezcano --- drivers/clocksource/cadence_ttc_timer.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/drivers/clocksource/cadence_ttc_timer.c b/drivers/clocksource/cadence_ttc_timer.c index b2bb3a4bc205..a92350b55d32 100644 --- a/drivers/clocksource/cadence_ttc_timer.c +++ b/drivers/clocksource/cadence_ttc_timer.c @@ -67,11 +67,13 @@ * struct ttc_timer - This definition defines local timer structure * * @base_addr: Base address of timer + * @freq: Timer input clock frequency * @clk: Associated clock source * @clk_rate_change_nb Notifier block for clock rate changes */ struct ttc_timer { void __iomem *base_addr; + unsigned long freq; struct clk *clk; struct notifier_block clk_rate_change_nb; }; @@ -196,9 +198,8 @@ static void ttc_set_mode(enum clock_event_mode mode, switch (mode) { case CLOCK_EVT_MODE_PERIODIC: - ttc_set_interval(timer, - DIV_ROUND_CLOSEST(clk_get_rate(ttce->ttc.clk), - PRESCALE * HZ)); + ttc_set_interval(timer, DIV_ROUND_CLOSEST(ttce->ttc.freq, + PRESCALE * HZ)); break; case CLOCK_EVT_MODE_ONESHOT: case CLOCK_EVT_MODE_UNUSED: @@ -273,6 +274,8 @@ static void __init ttc_setup_clocksource(struct clk *clk, void __iomem *base) return; } + ttccs->ttc.freq = clk_get_rate(ttccs->ttc.clk); + ttccs->ttc.clk_rate_change_nb.notifier_call = ttc_rate_change_clocksource_cb; ttccs->ttc.clk_rate_change_nb.next = NULL; @@ -298,16 +301,14 @@ static void __init ttc_setup_clocksource(struct clk *clk, void __iomem *base) __raw_writel(CNT_CNTRL_RESET, ttccs->ttc.base_addr + TTC_CNT_CNTRL_OFFSET); - err = clocksource_register_hz(&ttccs->cs, - clk_get_rate(ttccs->ttc.clk) / PRESCALE); + err = clocksource_register_hz(&ttccs->cs, ttccs->ttc.freq / PRESCALE); if (WARN_ON(err)) { kfree(ttccs); return; } ttc_sched_clock_val_reg = base + TTC_COUNT_VAL_OFFSET; - setup_sched_clock(ttc_sched_clock_read, 16, - clk_get_rate(ttccs->ttc.clk) / PRESCALE); + setup_sched_clock(ttc_sched_clock_read, 16, ttccs->ttc.freq / PRESCALE); } static int ttc_rate_change_clockevent_cb(struct notifier_block *nb, @@ -334,6 +335,9 @@ static int ttc_rate_change_clockevent_cb(struct notifier_block *nb, ndata->new_rate / PRESCALE); local_irq_restore(flags); + /* update cached frequency */ + ttc->freq = ndata->new_rate; + /* fall through */ } case PRE_RATE_CHANGE: @@ -367,6 +371,7 @@ static void __init ttc_setup_clockevent(struct clk *clk, if (clk_notifier_register(ttcce->ttc.clk, &ttcce->ttc.clk_rate_change_nb)) pr_warn("Unable to register clock notifier.\n"); + ttcce->ttc.freq = clk_get_rate(ttcce->ttc.clk); ttcce->ttc.base_addr = base; ttcce->ce.name = "ttc_clockevent"; @@ -396,7 +401,7 @@ static void __init ttc_setup_clockevent(struct clk *clk, } clockevents_config_and_register(&ttcce->ce, - clk_get_rate(ttcce->ttc.clk) / PRESCALE, 1, 0xfffe); + ttcce->ttc.freq / PRESCALE, 1, 0xfffe); } /**