[PATCH v3 13/13] clocksource/drivers/rockchip_timer: Prevent ftrace recursion
From: heiko@sntech.de (Heiko Stübner)
Date: 2016-11-29 15:03:15
Also in:
linux-devicetree, linux-rockchip, lkml
Am Dienstag, 29. November 2016, 16:45:18 schrieb Alexander Kochetkov:
Currently rockchip_timer can be used as a scheduler clock. We properly marked rk_timer_sched_clock_read() as notrace but we then call another function rk_timer_counter_read() that _wasn't_ notrace. Having a traceable function in the sched_clock() path leads to a recursion within ftrace and a kernel crash. Fix this by adding an extra notrace function to keep other users of rk_timer_counter_read() traceable. Signed-off-by: Alexander Kochetkov <redacted>
you introduced the issue yourself in patch 11/13. In general any patch should never leave the kernel in a worse state than it was before, so no patch should ever introduce known issues itself. In that line of thought, don't patches 10+11 introduce warnings about unused functions as well when applied without patch 12? Maybe merge them? Heiko
quoted hunk ↗ jump to hunk
--- drivers/clocksource/rockchip_timer.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)diff --git a/drivers/clocksource/rockchip_timer.cb/drivers/clocksource/rockchip_timer.c index 1af80a0..a127822 100644--- a/drivers/clocksource/rockchip_timer.c +++ b/drivers/clocksource/rockchip_timer.c@@ -87,7 +87,7 @@ static void rk_timer_update_counter(u64 cycles, structrk_timer *timer) writel_relaxed(upper, timer->base + TIMER_LOAD_COUNT1); } -static u64 rk_timer_counter_read(struct rk_timer *timer) +static u64 notrace _rk_timer_counter_read(struct rk_timer *timer) { u64 counter; u32 lower;@@ -106,6 +106,11 @@ static u64 rk_timer_counter_read(struct rk_timer*timer) return counter; } +static u64 rk_timer_counter_read(struct rk_timer *timer) +{ + return _rk_timer_counter_read(timer); +} + static void rk_timer_interrupt_clear(struct rk_timer *timer) { writel_relaxed(1, timer->base + TIMER_INT_STATUS);@@ -168,7 +173,7 @@ static u64 notrace rk_timer_sched_clock_read(void) { struct rk_clocksource *_cs = &cs_timer; - return ~rk_timer_counter_read(&_cs->timer); + return ~_rk_timer_counter_read(&_cs->timer); } static int __init rk_timer_init(struct device_node *np, u32 ctrl_reg)