From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: [PATCH v2 omap 2/6] arm: Use _rcuidle for suspend/resume tracepoints Date: Mon, 16 May 2016 11:50:04 -0700 Message-ID: <1463424608-20237-2-git-send-email-paulmck@linux.vnet.ibm.com> References: <20160516184844.GA20144@linux.vnet.ibm.com> Return-path: In-Reply-To: <20160516184844.GA20144@linux.vnet.ibm.com> Sender: linux-pm-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, linux-clk@vger.kernel.org Cc: tony@atomide.com, mingo@kernel.org, linux@roeck-us.net, rostedt@goodmis.org, "Paul E. McKenney" , Russell King , "Rafael J. Wysocki" , Pavel Machek List-Id: linux-omap@vger.kernel.org Further testing with false negatives suppressed by commit 293e2421fe25 ("rcu: Remove superfluous versions of rcu_read_lock_sched_held()") identified a few more unprotected uses of RCU from the idle loop. Because RCU actively ignores idle-loop code (for energy-efficiency reasons, among other things), using RCU from the idle loop can result in too-short grace periods, in turn resulting in arbitrary misbehavior. The affected functions are smp_cross_call() and rpm_suspend(). The resulting lockdep-RCU splats are as follows: ------------------------------------------------------------------------ =============================== [ INFO: suspicious RCU usage. ] 4.6.0-rc5-next-20160426+ #1112 Not tainted ------------------------------- include/trace/events/ipi.h:35 suspicious rcu_dereference_check() usage! other info that might help us debug this: RCU used illegally from idle CPU! rcu_scheduler_active = 1, debug_locks = 0 RCU used illegally from extended quiescent state! no locks held by swapper/0/0. stack backtrace: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.6.0-rc5-next-20160426+ #1112 Hardware name: Generic OMAP4 (Flattened Device Tree) [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [] (show_stack) from [] (dump_stack+0xb0/0xe4) [] (dump_stack) from [] (smp_cross_call+0xbc/0x188) [] (smp_cross_call) from [] (generic_exec_single+0x9c/0x15c) [] (generic_exec_single) from [] (smp_call_function_single_async+0 x38/0x9c) [] (smp_call_function_single_async) from [] (cpuidle_coupled_poke_others+0x8c/0xa8) [] (cpuidle_coupled_poke_others) from [] (cpuidle_enter_state_coupled+0x26c/0x390) [] (cpuidle_enter_state_coupled) from [] (cpu_startup_entry+0x198/0x3a0) [] (cpu_startup_entry) from [] (start_kernel+0x354/0x3c8) [] (start_kernel) from [<8000807c>] (0x8000807c) ------------------------------------------------------------------------ Warning from omap3 =============================== [ INFO: suspicious RCU usage. ] 4.6.0-rc5-next-20160426+ #1112 Not tainted ------------------------------- include/trace/events/rpm.h:63 suspicious rcu_dereference_check() usage! other info that might help us debug this: RCU used illegally from idle CPU! rcu_scheduler_active = 1, debug_locks = 0 RCU used illegally from extended quiescent state! 1 lock held by swapper/0/0: #0: (&(&dev->power.lock)->rlock){-.-...}, at: [] __pm_runtime_suspend+0x54/0x84 stack backtrace: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.6.0-rc5-next-20160426+ #1112 Hardware name: Generic OMAP36xx (Flattened Device Tree) [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [] (show_stack) from [] (dump_stack+0xb0/0xe4) [] (dump_stack) from [] (rpm_suspend+0x604/0x7e4) [] (rpm_suspend) from [] (__pm_runtime_suspend+0x64/0x84) [] (__pm_runtime_suspend) from [] (omap2_gpio_prepare_for_idle+0x5c/0x70) [] (omap2_gpio_prepare_for_idle) from [] (omap_sram_idle+0x140/0x244) [] (omap_sram_idle) from [] (omap3_enter_idle_bm+0xfc/0x1ec) [] (omap3_enter_idle_bm) from [] (cpuidle_enter_state+0x80/0x3d4) [] (cpuidle_enter_state) from [] (cpu_startup_entry+0x198/0x3a0) [] (cpu_startup_entry) from [] (start_kernel+0x354/0x3c8) [] (start_kernel) from [<8000807c>] (0x8000807c) ------------------------------------------------------------------------ Reported-by: Tony Lindgren Signed-off-by: Paul E. McKenney Tested-by: Tony Lindgren Cc: Russell King Cc: Steven Rostedt Cc: "Rafael J. Wysocki" Cc: Pavel Machek Cc: Cc: Cc: --- arch/arm/kernel/smp.c | 2 +- drivers/base/power/runtime.c | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index baee70267f29..7afe48ae5d76 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -486,7 +486,7 @@ static const char *ipi_types[NR_IPI] __tracepoint_string = { static void smp_cross_call(const struct cpumask *target, unsigned int ipinr) { - trace_ipi_raise(target, ipi_types[ipinr]); + trace_ipi_raise_rcuidle(target, ipi_types[ipinr]); __smp_cross_call(target, ipinr); } diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 4c7055009bd6..ad115568ce58 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -419,7 +419,7 @@ static int rpm_suspend(struct device *dev, int rpmflags) struct device *parent = NULL; int retval; - trace_rpm_suspend(dev, rpmflags); + trace_rpm_suspend_rcuidle(dev, rpmflags); repeat: retval = rpm_check_suspend_allowed(dev); @@ -549,7 +549,7 @@ static int rpm_suspend(struct device *dev, int rpmflags) } out: - trace_rpm_return_int(dev, _THIS_IP_, retval); + trace_rpm_return_int_rcuidle(dev, _THIS_IP_, retval); return retval; -- 2.5.2