From 0b9a29add43273e64ef45472e08d38116fee1d82 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 24 Apr 2016 14:30:16 -0700 Subject: [PATCH] arm: Use _rcuidle tracepoint to allow use from idle Testing on ARM encountered the following pair of lockdep-RCU splats: ------------------------------------------------------------------------ =============================== [ INFO: suspicious RCU usage. ] 4.6.0-rc4-next-20160422 #1 Not tainted ------------------------------- include/trace/events/power.h:328 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-rc4-next-20160422 #1 Hardware name: Generic OMAP3-GP (Flattened Device Tree) [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [] (show_stack) from [] (dump_stack+0xa8/0xe0) [] (dump_stack) from [] (pwrdm_set_next_pwrst+0xf8/0x1cc) [] (pwrdm_set_next_pwrst) from [] (omap3_enter_idle_bm+0x1b8/0x1e8) [] (omap3_enter_idle_bm) from [] (cpuidle_enter_state+0x84/0x408) [] (cpuidle_enter_state) from [] (cpu_startup_entry+0x1c8/0x3f0) [] (cpu_startup_entry) from [] (start_kernel+0x354/0x3cc) ------------------------------------------------------------------------ [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [] (show_stack) from [] (dump_stack+0xa8/0xe0) [] (dump_stack) from [] (_pwrdm_state_switch+0x188/0x32c) [] (_pwrdm_state_switch) from [] (_pwrdm_post_transition_cb+0xc/0x14) [] (_pwrdm_post_transition_cb) from [] (pwrdm_for_each+0x30/0x5c) [] (pwrdm_for_each) from [] (pwrdm_post_transition+0x24/0x30) [] (pwrdm_post_transition) from [] (omap_sram_idle+0xfc/0x240) [] (omap_sram_idle) from [] (omap3_enter_idle_bm+0xf0/0x1e8) [] (omap3_enter_idle_bm) from [] (cpuidle_enter_state+0x84/0x408) [] (cpuidle_enter_state) from [] (cpu_startup_entry+0x1c8/0x3f0) [] (cpu_startup_entry) from [] (start_kernel+0x354/0x3cc) ------------------------------------------------------------------------ These are caused by event tracing from the idle loop, and they were exposed by commit 293e2421fe25 ("rcu: Remove superfluous versions of rcu_read_lock_sched_held()"), which suppressed some false negatives. The current commit therefore adds the _rcuidle suffix to make RCU aware of this implicit use of RCU by event tracing, thus preventing both splats. Reported-by: Guenter Roeck Signed-off-by: Paul E. McKenney Tested-by: Guenter Roeck Tested-by: Tony Lindgren Cc: Russell King Reviewed-by: Steven Rostedt Cc: Cc: --- arch/arm/mach-omap2/powerdomain.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/arm/mach-omap2/powerdomain.c b/arch/arm/mach-omap2/powerdomain.c index 78af6d8..daf2753 100644 --- a/arch/arm/mach-omap2/powerdomain.c +++ b/arch/arm/mach-omap2/powerdomain.c @@ -186,8 +186,9 @@ static int _pwrdm_state_switch(struct powerdomain *pwrdm, int flag) trace_state = (PWRDM_TRACE_STATES_FLAG | ((next & OMAP_POWERSTATE_MASK) << 8) | ((prev & OMAP_POWERSTATE_MASK) << 0)); - trace_power_domain_target(pwrdm->name, trace_state, - smp_processor_id()); + trace_power_domain_target_rcuidle(pwrdm->name, + trace_state, + smp_processor_id()); } break; default: @@ -523,8 +524,8 @@ int pwrdm_set_next_pwrst(struct powerdomain *pwrdm, u8 pwrst) if (arch_pwrdm && arch_pwrdm->pwrdm_set_next_pwrst) { /* Trace the pwrdm desired target state */ - trace_power_domain_target(pwrdm->name, pwrst, - smp_processor_id()); + trace_power_domain_target_rcuidle(pwrdm->name, pwrst, + smp_processor_id()); /* Program the pwrdm desired target state */ ret = arch_pwrdm->pwrdm_set_next_pwrst(pwrdm, pwrst); } -- 2.7.4