diff options
author | Soren Brinkmann <soren.brinkmann@xilinx.com> | 2013-11-27 01:04:50 (GMT) |
---|---|---|
committer | Daniel Lezcano <daniel.lezcano@linaro.org> | 2013-12-30 10:32:24 (GMT) |
commit | c1dcc927dae01dfd4904ee82ce2c00b50eab6dc3 (patch) | |
tree | a48598475900901e31c1c397a2bdb8d085092ea1 /drivers/clocksource/cadence_ttc_timer.c | |
parent | b0031f227e47919797dc0e1c1990f3ef151ff0cc (diff) | |
download | linux-c1dcc927dae01dfd4904ee82ce2c00b50eab6dc3.tar.xz |
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
[<c0014a78>] (unwind_backtrace+0x0/0x11c) from [<c0011b6c>] (show_stack+0x10/0x14)
[<c0011b6c>] (show_stack+0x10/0x14) from [<c039120c>] (dump_stack+0x7c/0xc0)
[<c039120c>] (dump_stack+0x7c/0xc0) from [<c001fda4>] (warn_slowpath_common+0x60/0x84)
[<c001fda4>] (warn_slowpath_common+0x60/0x84) from [<c001fe48>] (warn_slowpath_fmt+0x2c/0x3c)
[<c001fe48>] (warn_slowpath_fmt+0x2c/0x3c) from [<c0392658>] (mutex_trylock+0x70/0x1fc)
[<c0392658>] (mutex_trylock+0x70/0x1fc) from [<c02dfc08>] (clk_prepare_lock+0xc/0xe4)
[<c02dfc08>] (clk_prepare_lock+0xc/0xe4) from [<c02e099c>] (clk_get_rate+0xc/0x44)
[<c02e099c>] (clk_get_rate+0xc/0x44) from [<c02d0394>] (ttc_set_mode+0x34/0x78)
[<c02d0394>] (ttc_set_mode+0x34/0x78) from [<c005f794>] (clockevents_set_mode+0x28/0x5c)
[<c005f794>] (clockevents_set_mode+0x28/0x5c) from [<c00607fc>] (tick_broadcast_on_off+0x190/0x1c0)
[<c00607fc>] (tick_broadcast_on_off+0x190/0x1c0) from [<c005f168>] (clockevents_notify+0x58/0x1ac)
[<c005f168>] (clockevents_notify+0x58/0x1ac) from [<c02b99dc>] (cpuidle_setup_broadcast_timer+0x20/0x24)
[<c02b99dc>] (cpuidle_setup_broadcast_timer+0x20/0x24) from [<c006cd04>] (generic_smp_call_function_single_interrupt+0)
[<c006cd04>] (generic_smp_call_function_single_interrupt+0xe0/0x130) from [<c00138c8>] (handle_IPI+0x88/0x118)
[<c00138c8>] (handle_IPI+0x88/0x118) from [<c0008504>] (gic_handle_irq+0x58/0x60)
[<c0008504>] (gic_handle_irq+0x58/0x60) from [<c0012644>] (__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
[<c0012644>] (__irq_svc+0x44/0x78) from [<c000f46c>] (arch_cpu_idle+0x34/0x3c)
[<c000f46c>] (arch_cpu_idle+0x34/0x3c) from [<c0053980>] (cpu_startup_entry+0xa8/0x10c)
[<c0053980>] (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 <daniel.lezcano@linaro.org>
Tested-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Diffstat (limited to 'drivers/clocksource/cadence_ttc_timer.c')
-rw-r--r-- | drivers/clocksource/cadence_ttc_timer.c | 21 |
1 files changed, 13 insertions, 8 deletions
diff --git a/drivers/clocksource/cadence_ttc_timer.c b/drivers/clocksource/cadence_ttc_timer.c index b2bb3a4b..a92350b 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); } /** |