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authorThierry Reding <treding@nvidia.com>2015-09-10 15:55:21 +0200
committerStephen Boyd <sboyd@codeaurora.org>2015-09-16 15:16:03 -0700
commite1595d89ae8180e0d3815cc75336ac3484de0aa0 (patch)
treee3c79b1d6f65755e3463e64492e3579727cba5bb
parent380528f742796e1244e931c51e77c9ed664f566c (diff)
downloadop-kernel-dev-e1595d89ae8180e0d3815cc75336ac3484de0aa0.zip
op-kernel-dev-e1595d89ae8180e0d3815cc75336ac3484de0aa0.tar.gz
clk: tegra: dfll: Properly protect OPP list
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: =============================== [ INFO: suspicious RCU usage. ] 4.2.0-next-20150908 #1 Not tainted ------------------------------- drivers/base/power/opp.c:460 Missing rcu_read_lock() or dev_opp_list_lock protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 0 4 locks held by kworker/u8:0/6: #0: ("%s""deferwq"){++++.+}, at: [<c0040d8c>] process_one_work+0x118/0x4bc #1: (deferred_probe_work){+.+.+.}, at: [<c0040d8c>] process_one_work+0x118/0x4bc #2: (&dev->mutex){......}, at: [<c03b8194>] __device_attach+0x20/0x118 #3: (prepare_lock){+.+...}, at: [<c054bc08>] clk_prepare_lock+0x10/0xf8 stack backtrace: CPU: 2 PID: 6 Comm: kworker/u8:0 Not tainted 4.2.0-next-20150908 #1 Hardware name: NVIDIA Tegra SoC (Flattened Device Tree) Workqueue: deferwq deferred_probe_work_func [<c001802c>] (unwind_backtrace) from [<c00135a4>] (show_stack+0x10/0x14) [<c00135a4>] (show_stack) from [<c02a8418>] (dump_stack+0x94/0xd4) [<c02a8418>] (dump_stack) from [<c03c6f6c>] (dev_pm_opp_find_freq_ceil+0x108/0x114) [<c03c6f6c>] (dev_pm_opp_find_freq_ceil) from [<c0551a3c>] (dfll_calculate_rate_request+0xb8/0x170) [<c0551a3c>] (dfll_calculate_rate_request) from [<c0551b10>] (dfll_clk_round_rate+0x1c/0x2c) [<c0551b10>] (dfll_clk_round_rate) from [<c054de2c>] (clk_calc_new_rates+0x1b8/0x228) [<c054de2c>] (clk_calc_new_rates) from [<c054e44c>] (clk_core_set_rate_nolock+0x44/0xac) [<c054e44c>] (clk_core_set_rate_nolock) from [<c054e4d8>] (clk_set_rate+0x24/0x34) [<c054e4d8>] (clk_set_rate) from [<c0512460>] (tegra124_cpufreq_probe+0x120/0x230) [<c0512460>] (tegra124_cpufreq_probe) from [<c03b9cbc>] (platform_drv_probe+0x44/0xac) [<c03b9cbc>] (platform_drv_probe) from [<c03b84c8>] (driver_probe_device+0x218/0x304) [<c03b84c8>] (driver_probe_device) from [<c03b69b0>] (bus_for_each_drv+0x60/0x94) [<c03b69b0>] (bus_for_each_drv) from [<c03b8228>] (__device_attach+0xb4/0x118) ata1: SATA link down (SStatus 0 SControl 300) [<c03b8228>] (__device_attach) from [<c03b77c8>] (bus_probe_device+0x88/0x90) [<c03b77c8>] (bus_probe_device) from [<c03b7be8>] (deferred_probe_work_func+0x58/0x8c) [<c03b7be8>] (deferred_probe_work_func) from [<c0040dfc>] (process_one_work+0x188/0x4bc) [<c0040dfc>] (process_one_work) from [<c004117c>] (worker_thread+0x4c/0x4f4) [<c004117c>] (worker_thread) from [<c0047230>] (kthread+0xe4/0xf8) [<c0047230>] (kthread) from [<c000f7d0>] (ret_from_fork+0x14/0x24) Signed-off-by: Thierry Reding <treding@nvidia.com> Fixes: c4fe70ada40f ("clk: tegra: Add closed loop support for the DFLL") [vince.h@nvidia.com: Unlock rcu on error path] Signed-off-by: Vince Hsu <vince.h@nvidia.com> [sboyd@codeaurora.org: Dropped second hunk that nested the rcu read lock unnecessarily] Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
-rw-r--r--drivers/clk/tegra/clk-dfll.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/clk/tegra/clk-dfll.c b/drivers/clk/tegra/clk-dfll.c
index c2ff859..c4e3a52 100644
--- a/drivers/clk/tegra/clk-dfll.c
+++ b/drivers/clk/tegra/clk-dfll.c
@@ -682,11 +682,17 @@ 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))
+ if (IS_ERR(opp)) {
+ rcu_read_unlock();
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;
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