From 398f74569cebbf06bc6b069442bcd0e9616ca465 Mon Sep 17 00:00:00 2001 From: Stephen Boyd Date: Fri, 19 Jun 2015 21:37:56 +0100 Subject: [PATCH] ARM: 8393/1: smp: Fix suspicious RCU usage with ipi tracepoints John Stultz reports an RCU splat on boot with ARM ipi trace events enabled. =============================== [ INFO: suspicious RCU usage. ] 4.1.0-rc7-00033-gb5bed2f #153 Not tainted ------------------------------- include/trace/events/ipi.h:68 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 4.1.0-rc7-00033-gb5bed2f #153 Hardware name: Qualcomm (Flattened Device Tree) [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [] (show_stack) from [] (dump_stack+0x70/0xbc) [] (dump_stack) from [] (handle_IPI+0x428/0x604) [] (handle_IPI) from [] (gic_handle_irq+0x54/0x5c) [] (gic_handle_irq) from [] (__irq_svc+0x44/0x7c) Exception stack(0xc09f3f48 to 0xc09f3f90) 3f40: 00000001 00000001 00000000 c09f73b8 c09f4528 c0a5de9c 3f60: c076b4f0 00000000 00000000 c09ef108 c0a5cec1 00000001 00000000 c09f3f90 3f80: c026bf60 c0210ab8 20000113 ffffffff [] (__irq_svc) from [] (arch_cpu_idle+0x20/0x3c) [] (arch_cpu_idle) from [] (cpu_startup_entry+0x2c0/0x5dc) [] (cpu_startup_entry) from [] (start_kernel+0x358/0x3c4) [] (start_kernel) from [<8020807c>] (0x8020807c) At this point in the IPI handling path we haven't called irq_enter() yet, so RCU doesn't know that we're about to exit idle and properly warns that we're using RCU from an idle CPU. Use trace_ipi_entry_rcuidle() instead of trace_ipi_entry() so that RCU is informed about our exit from idle. Fixes: 365ec7b17327 ("ARM: add IPI tracepoints") Reported-by: John Stultz Tested-by: John Stultz Acked-by: Steven Rostedt Reviewed-by: Paul E. McKenney Signed-off-by: Stephen Boyd Signed-off-by: Russell King --- arch/arm/kernel/smp.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c index cca5b8758185..f11d82527076 100644 --- a/arch/arm/kernel/smp.c +++ b/arch/arm/kernel/smp.c @@ -576,7 +576,7 @@ void handle_IPI(int ipinr, struct pt_regs *regs) struct pt_regs *old_regs = set_irq_regs(regs); if ((unsigned)ipinr < NR_IPI) { - trace_ipi_entry(ipi_types[ipinr]); + trace_ipi_entry_rcuidle(ipi_types[ipinr]); __inc_irq_stat(cpu, ipi_irqs[ipinr]); } @@ -635,7 +635,7 @@ void handle_IPI(int ipinr, struct pt_regs *regs) } if ((unsigned)ipinr < NR_IPI) - trace_ipi_exit(ipi_types[ipinr]); + trace_ipi_exit_rcuidle(ipi_types[ipinr]); set_irq_regs(old_regs); } -- 2.20.1