From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thierry Reding Subject: [PATCH] clk: tegra: dfll: Properly protect OPP list Date: Thu, 10 Sep 2015 15:55:21 +0200 Message-ID: <1441893321-4563-1-git-send-email-thierry.reding@gmail.com> Return-path: Sender: linux-clk-owner@vger.kernel.org To: Thierry Reding Cc: Alexandre Courbot , Stephen Warren , Mikko Perttunen , Tuomas Tynkkynen , Viresh Kumar , Stephen Boyd , Krzysztof Kozlowski , "Rafael J. Wysocki" , linux-pm@vger.kernel.org, linux-clk@vger.kernel.org, linux-tegra@vger.kernel.org List-Id: linux-pm@vger.kernel.org From: Thierry Reding The OPP list needs to be protected against concurrent accesses. Using simple RCU read locks does the trick and gets rid of the following lockdep warning: [ 9.095873] =============================== [ 9.100050] [ INFO: suspicious RCU usage. ] [ 9.104313] 4.2.0-next-20150908 #1 Not tainted [ 9.111187] ------------------------------- [ 9.115428] drivers/base/power/opp.c:460 Missing rcu_read_lock() or dev_opp_list_lock protection! [ 9.128519] [ 9.128519] other info that might help us debug this: [ 9.128519] [ 9.136651] [ 9.136651] rcu_scheduler_active = 1, debug_locks = 0 [ 9.143222] 4 locks held by kworker/u8:0/6: [ 9.147409] #0: ("%s""deferwq"){++++.+}, at: [] process_one_work+0x118/0x4bc [ 9.155610] #1: (deferred_probe_work){+.+.+.}, at: [] process_one_work+0x118/0x4bc [ 9.164335] #2: (&dev->mutex){......}, at: [] __device_attach+0x20/0x118 [ 9.172134] #3: (prepare_lock){+.+...}, at: [] clk_prepare_lock+0x10/0xf8 [ 9.180365] [ 9.180365] stack backtrace: [ 9.184764] CPU: 2 PID: 6 Comm: kworker/u8:0 Not tainted 4.2.0-next-20150908 #1 [ 9.194536] Hardware name: NVIDIA Tegra SoC (Flattened Device Tree) [ 9.200809] Workqueue: deferwq deferred_probe_work_func [ 9.206115] [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [ 9.213918] [] (show_stack) from [] (dump_stack+0x94/0xd4) [ 9.221142] [] (dump_stack) from [] (dev_pm_opp_find_freq_ceil+0x108/0x114) [ 9.229903] [] (dev_pm_opp_find_freq_ceil) from [] (dfll_calculate_rate_request+0xb8/0x170) [ 9.240041] [] (dfll_calculate_rate_request) from [] (dfll_clk_round_rate+0x1c/0x2c) [ 9.249560] [] (dfll_clk_round_rate) from [] (clk_calc_new_rates+0x1b8/0x228) [ 9.258473] [] (clk_calc_new_rates) from [] (clk_core_set_rate_nolock+0x44/0xac) [ 9.267647] [] (clk_core_set_rate_nolock) from [] (clk_set_rate+0x24/0x34) [ 9.276306] [] (clk_set_rate) from [] (tegra124_cpufreq_probe+0x120/0x230) [ 9.284944] [] (tegra124_cpufreq_probe) from [] (platform_drv_probe+0x44/0xac) [ 9.293948] [] (platform_drv_probe) from [] (driver_probe_device+0x218/0x304) [ 9.302816] [] (driver_probe_device) from [] (bus_for_each_drv+0x60/0x94) [ 9.311397] [] (bus_for_each_drv) from [] (__device_attach+0xb4/0x118) [ 9.313229] ata1: SATA link down (SStatus 0 SControl 300) [ 9.325137] [] (__device_attach) from [] (bus_probe_device+0x88/0x90) [ 9.333360] [] (bus_probe_device) from [] (deferred_probe_work_func+0x58/0x8c) [ 9.342338] [] (deferred_probe_work_func) from [] (process_one_work+0x188/0x4bc) [ 9.351526] [] (process_one_work) from [] (worker_thread+0x4c/0x4f4) [ 9.359690] [] (worker_thread) from [] (kthread+0xe4/0xf8) [ 9.366970] [] (kthread) from [] (ret_from_fork+0x14/0x24) Signed-off-by: Thierry Reding --- drivers/clk/tegra/clk-dfll.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/clk/tegra/clk-dfll.c b/drivers/clk/tegra/clk-dfll.c index aa026bcf5b00..8e25bd52da8c 100644 --- a/drivers/clk/tegra/clk-dfll.c +++ b/drivers/clk/tegra/clk-dfll.c @@ -632,11 +632,15 @@ static int find_lut_index_for_rate(struct tegra_dfll *td, unsigned long rate) struct dev_pm_opp *opp; int i, uv; + rcu_read_lock(); + opp = dev_pm_opp_find_freq_ceil(td->soc->dev, &rate); if (IS_ERR(opp)) return PTR_ERR(opp); uv = dev_pm_opp_get_voltage(opp); + rcu_read_unlock(); + for (i = 0; i < td->i2c_lut_size; i++) { if (regulator_list_voltage(td->vdd_reg, td->i2c_lut[i]) == uv) return i; @@ -1450,6 +1454,8 @@ static int dfll_build_i2c_lut(struct tegra_dfll *td) td->i2c_lut[0] = lut; for (j = 1, rate = 0; ; rate++) { + rcu_read_lock(); + opp = dev_pm_opp_find_freq_ceil(td->soc->dev, &rate); if (IS_ERR(opp)) break; @@ -1458,6 +1464,8 @@ static int dfll_build_i2c_lut(struct tegra_dfll *td) if (v_opp <= td->soc->min_millivolts * 1000) td->dvco_rate_min = dev_pm_opp_get_freq(opp); + rcu_read_unlock(); + for (;;) { v += max(1, (v_max - v) / (MAX_DFLL_VOLTAGES - j)); if (v >= v_opp) -- 2.5.0