From b47430d3adbedbfdb5979ba4874f5dadf94f16b1 Mon Sep 17 00:00:00 2001 From: "Srivatsa S. Bhat" Date: Tue, 14 May 2013 04:01:27 +0530 Subject: rcu/idle: Wrap cpu-idle poll mode within rcu_idle_enter/exit MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Bjørn Mork reported the following warning when running powertop. [ 49.289034] ------------[ cut here ]------------ [ 49.289055] WARNING: at kernel/rcutree.c:502 rcu_eqs_exit_common.isra.48+0x3d/0x125() [ 49.289244] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-bisect-rcu-warn+ #107 [ 49.289251] ffffffff8157d8c8 ffffffff81801e28 ffffffff8137e4e3 ffffffff81801e68 [ 49.289260] ffffffff8103094f ffffffff81801e68 0000000000000000 ffff88023afcd9b0 [ 49.289268] 0000000000000000 0140000000000000 ffff88023bee7700 ffffffff81801e78 [ 49.289276] Call Trace: [ 49.289285] [] dump_stack+0x19/0x1b [ 49.289293] [] warn_slowpath_common+0x62/0x7b [ 49.289300] [] warn_slowpath_null+0x15/0x17 [ 49.289306] [] rcu_eqs_exit_common.isra.48+0x3d/0x125 [ 49.289314] [] ? trace_hardirqs_off_caller+0x37/0xa6 [ 49.289320] [] rcu_idle_exit+0x85/0xa8 [ 49.289327] [] trace_cpu_idle_rcuidle+0xae/0xff [ 49.289334] [] cpu_startup_entry+0x72/0x115 [ 49.289341] [] rest_init+0x149/0x150 [ 49.289347] [] ? csum_partial_copy_generic+0x16c/0x16c [ 49.289355] [] start_kernel+0x3f0/0x3fd [ 49.289362] [] ? repair_env_string+0x5a/0x5a [ 49.289368] [] x86_64_start_reservations+0x2a/0x2c [ 49.289375] [] x86_64_start_kernel+0xcd/0xd1 [ 49.289379] ---[ end trace 07a1cc95e29e9036 ]--- The warning is that 'rdtp->dynticks' has an unexpected value, which roughly translates to - the calls to rcu_idle_enter() and rcu_idle_exit() were not made in the correct order, or otherwise messed up. And Bjørn's painstaking debugging indicated that this happens when the idle loop enters the poll mode. Looking at the poll function cpu_idle_poll(), and the implementation of trace_cpu_idle_rcuidle(), the problem becomes very clear: cpu_idle_poll() lacks calls to rcu_idle_enter/exit(), and trace_cpu_idle_rcuidle() calls them in the reverse order - first rcu_idle_exit(), and then rcu_idle_enter(). Hence the even/odd alternative sequencing of rdtp->dynticks goes for a toss. And powertop readily triggers this because powertop uses the idle-tracing infrastructure extensively. So, to fix this, wrap the code in cpu_idle_poll() within rcu_idle_enter/exit(), so that it blends properly with the calls inside trace_cpu_idle_rcuidle() and thus get the function ordering right. Reported-and-tested-by: Bjørn Mork Cc: Paul McKenney Cc: Steven Rostedt Cc: Dipankar Sarma Signed-off-by: Srivatsa S. Bhat Link: http://lkml.kernel.org/r/519169BF.4080208@linux.vnet.ibm.com Signed-off-by: Thomas Gleixner --- kernel/cpu/idle.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel/cpu/idle.c') diff --git a/kernel/cpu/idle.c b/kernel/cpu/idle.c index 8b86c0c68edf..d5585f5e038e 100644 --- a/kernel/cpu/idle.c +++ b/kernel/cpu/idle.c @@ -40,11 +40,13 @@ __setup("hlt", cpu_idle_nopoll_setup); static inline int cpu_idle_poll(void) { + rcu_idle_enter(); trace_cpu_idle_rcuidle(0, smp_processor_id()); local_irq_enable(); while (!need_resched()) cpu_relax(); trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); + rcu_idle_exit(); return 1; } -- cgit v1.2.3 From d7880812b3594d3c6dcbe3cfd71dabb17347d082 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 10 Jun 2013 16:52:03 +0200 Subject: idle: Add the stack canary init to cpu_startup_entry() Moving x86 to the generic idle implementation (commit 7d1a9417 "x86: Use generic idle loop") wreckaged the stack protector. I stupidly missed that boot_init_stack_canary() must be inlined from a function which never returns, but I put that call into arch_cpu_idle_prepare() which of course returns. I pondered to play tricks with arch_cpu_idle_prepare() first, but then I noticed, that the other archs which have implemented the stackprotector (ARM and SH) do not initialize the canary for the non-boot cpus. So I decided to move the boot_init_stack_canary() call into cpu_startup_entry() ifdeffed with an CONFIG_X86 for now. This #ifdef is just a temporary measure as I don't want to inflict the boot_init_stack_canary() call on ARM and SH that late in the cycle. I'll queue a patch for 3.11 which removes the #ifdef if the ARM/SH maintainers have no objection. Reported-by: Wouter van Kesteren Cc: x86@kernel.org Cc: Russell King Cc: Paul Mundt Signed-off-by: Thomas Gleixner --- arch/x86/kernel/process.c | 12 ------------ kernel/cpu/idle.c | 16 ++++++++++++++++ 2 files changed, 16 insertions(+), 12 deletions(-) (limited to 'kernel/cpu/idle.c') diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 4e7a37ff03ab..81a5f5e8f142 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -277,18 +277,6 @@ void exit_idle(void) } #endif -void arch_cpu_idle_prepare(void) -{ - /* - * If we're the non-boot CPU, nothing set the stack canary up - * for us. CPU0 already has it initialized but no harm in - * doing it again. This is a good place for updating it, as - * we wont ever return from this function (so the invalid - * canaries already on the stack wont ever trigger). - */ - boot_init_stack_canary(); -} - void arch_cpu_idle_enter(void) { local_touch_nmi(); diff --git a/kernel/cpu/idle.c b/kernel/cpu/idle.c index d5585f5e038e..bf2ee1aafa0e 100644 --- a/kernel/cpu/idle.c +++ b/kernel/cpu/idle.c @@ -5,6 +5,7 @@ #include #include #include +#include #include @@ -112,6 +113,21 @@ static void cpu_idle_loop(void) void cpu_startup_entry(enum cpuhp_state state) { + /* + * This #ifdef needs to die, but it's too late in the cycle to + * make this generic (arm and sh have never invoked the canary + * init for the non boot cpus!). Will be fixed in 3.11 + */ +#ifdef CONFIG_X86 + /* + * If we're the non-boot CPU, nothing set the stack canary up + * for us. The boot CPU already has it initialized but no harm + * in doing it again. This is a good place for updating it, as + * we wont ever return from this function (so the invalid + * canaries already on the stack wont ever trigger). + */ + boot_init_stack_canary(); +#endif current_set_polling(); arch_cpu_idle_prepare(); cpu_idle_loop(); -- cgit v1.2.3 From 29ce3785b22da47c49f4ef6e14b9014fa5dee261 Mon Sep 17 00:00:00 2001 From: James Bottomley Date: Wed, 8 May 2013 14:05:34 -0700 Subject: idle: Enable interrupts in the weak arch_cpu_idle() implementation PARISC bootup triggers the warning at kernel/cpu/idle.c:96. That's caused by the weak arch_cpu_idle() implementation, which is provided to avoid that architectures implement idle_poll over and over. The switchover to polling mode happens in the first call of the weak arch_cpu_idle() implementation, but that code fails to reenable interrupts and therefor triggers the warning. Fix this by enabling interrupts in the weak arch_cpu_idle() code. [ tglx: Made the changelog match the patch ] Signed-off-by: James Bottomley Reviewed-by: Srivatsa S. Bhat Link: http://lkml.kernel.org/r/1371236142.2726.43.camel@dabdike Signed-off-by: Thomas Gleixner --- kernel/cpu/idle.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/cpu/idle.c') diff --git a/kernel/cpu/idle.c b/kernel/cpu/idle.c index bf2ee1aafa0e..e695c0a0bcb5 100644 --- a/kernel/cpu/idle.c +++ b/kernel/cpu/idle.c @@ -59,6 +59,7 @@ void __weak arch_cpu_idle_dead(void) { } void __weak arch_cpu_idle(void) { cpu_idle_force_poll = 1; + local_irq_enable(); } /* -- cgit v1.2.3