From mboxrd@z Thu Jan 1 00:00:00 1970 From: dingtianhong@huawei.com (Ding Tianhong) Date: Thu, 6 Jul 2017 20:49:33 +0800 Subject: [PATCH] arm64: arch_timer: fix the infinite recursion when enable ftrace and erratum workaround Message-ID: <43ec809d-b8f2-eb73-8ad6-9966cf67625f@huawei.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org When enable preempt and ftrace, and perform the following steps, the system will hang: mount -t debugfs nodev /sys/kernel/debug/ cd /sys/kernel/debug/tracing/ echo function_graph > current_tracer This is because the preempt_disable and preempt_enable calls would cause infinite recursion for some chips which needs the timer erratum workaround and the system will hang, so use the preempt_disable/enable_notrace calls to prevent recursion. Fixes: 6acc71ccac71 ("arm64: arch_timer: Allows a CPU-specific erratum to only affect a subset of CPUs") Signed-off-by: Ding Tianhong --- arch/arm64/include/asm/arch_timer.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h index 74d08e4..67bb7a4 100644 --- a/arch/arm64/include/asm/arch_timer.h +++ b/arch/arm64/include/asm/arch_timer.h @@ -65,13 +65,13 @@ struct arch_timer_erratum_workaround { u64 _val; \ if (needs_unstable_timer_counter_workaround()) { \ const struct arch_timer_erratum_workaround *wa; \ - preempt_disable(); \ + preempt_disable_notrace(); \ wa = __this_cpu_read(timer_unstable_counter_workaround); \ if (wa && wa->read_##reg) \ _val = wa->read_##reg(); \ else \ _val = read_sysreg(reg); \ - preempt_enable(); \ + preempt_enable_notrace(); \ } else { \ _val = read_sysreg(reg); \ } \ -- 1.9.0