BMC/Intel-BMC/linux.git/arch/x86/kernel/smp.c, branch dev

x86: Consolidate irq entering inlines

2015-05-15T14:04:49+00:00

smp.c and irq_work.c implement the same inline helper. Move it to apic.h and use it everywhere. Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra

asmlinkage, x86: Add explicit __visible to arch/x86/*

2014-05-05T23:07:44+00:00

As requested by Linus add explicit __visible to the asmlinkage users. This marks all functions visible to assembler. Tree sweep for arch/x86/* Signed-off-by: Andi Kleen Link: http://lkml.kernel.org/r/1398984278-29319-3-git-send-email-andi@firstfloor.org Signed-off-by: H. Peter Anvin

x86, asmlinkage: Make all interrupt handlers asmlinkage / __visible

2013-08-06T21:18:23+00:00

These handlers are all referenced from assembler stubs, so need to be visible. The handlers without arguments become asmlinkage, the others __visible to not force regparms(0) on x86-32. I put it all into a single patch, please let me know if you want it it split up. Signed-off-by: Andi Kleen Link: http://lkml.kernel.org/r/1375740170-7446-4-git-send-email-andi@firstfloor.org Signed-off-by: H. Peter Anvin

x86/tracing: Add irq_enter/exit() in smp_trace_reschedule_interrupt()

2013-07-02T07:52:31+00:00

Reschedule vector tracepoints may be called in cpu idle state. This causes lockdep check warning below. The tracepoint requires rcu but for accuracy it also requires irq_enter() (tracepoints record the irq context), thus, the tracepoint interrupt handler should be calling irq_enter() and not rcu_irq_enter() (irq_enter() calls rcu_irq_enter()). So, add irq_enter/exit() to smp_trace_reschedule_interrupt() with common pre/post processing functions, smp_entering_irq() and exiting_irq() (exiting_irq() calls just irq_exit() in arch/x86/include/asm/apic.h), because these can be shared among reschedule, call_function, and call_function_single vectors. [ 50.720557] Testing event reschedule_exit: [ 50.721349] [ 50.721502] =============================== [ 50.721835] [ INFO: suspicious RCU usage. ] [ 50.722169] 3.10.0-rc6-00004-gcf910e8 #190 Not tainted [ 50.722582] ------------------------------- [ 50.722915] /c/kernel-tests/src/linux/arch/x86/include/asm/trace/irq_vectors.h:50 suspicious rcu_dereference_check() usage! [ 50.723770] [ 50.723770] other info that might help us debug this: [ 50.723770] [ 50.724385] [ 50.724385] RCU used illegally from idle CPU! [ 50.724385] rcu_scheduler_active = 1, debug_locks = 0 [ 50.725232] RCU used illegally from extended quiescent state! [ 50.725690] no locks held by swapper/0/0. [ 50.726010] [ 50.726010] stack backtrace: [...] Signed-off-by: Seiji Aguchi Reviewed-by: Steven Rostedt Link: http://lkml.kernel.org/r/51CDCFA3.9080101@hds.com Signed-off-by: Ingo Molnar

x86, trace: Add irq vector tracepoints

2013-06-21T05:25:34+00:00

[Purpose of this patch] As Vaibhav explained in the thread below, tracepoints for irq vectors are useful. http://www.spinics.net/lists/mm-commits/msg85707.html The current interrupt traces from irq_handler_entry and irq_handler_exit provide when an interrupt is handled. They provide good data about when the system has switched to kernel space and how it affects the currently running processes. There are some IRQ vectors which trigger the system into kernel space, which are not handled in generic IRQ handlers. Tracing such events gives us the information about IRQ interaction with other system events. The trace also tells where the system is spending its time. We want to know which cores are handling interrupts and how they are affecting other processes in the system. Also, the trace provides information about when the cores are idle and which interrupts are changing that state. On the other hand, my usecase is tracing just local timer event and getting a value of instruction pointer. I suggested to add an argument local timer event to get instruction pointer before. But there is another way to get it with external module like systemtap. So, I don't need to add any argument to irq vector tracepoints now. [Patch Description] Vaibhav's patch shared a trace point ,irq_vector_entry/irq_vector_exit, in all events. But there is an above use case to trace specific irq_vector rather than tracing all events. In this case, we are concerned about overhead due to unwanted events. So, add following tracepoints instead of introducing irq_vector_entry/exit. so that we can enable them independently. - local_timer_vector - reschedule_vector - call_function_vector - call_function_single_vector - irq_work_entry_vector - error_apic_vector - thermal_apic_vector - threshold_apic_vector - spurious_apic_vector - x86_platform_ipi_vector Also, introduce a logic switching IDT at enabling/disabling time so that a time penalty makes a zero when tracepoints are disabled. Detailed explanations are as follows. - Create trace irq handlers with entering_irq()/exiting_irq(). - Create a new IDT, trace_idt_table, at boot time by adding a logic to _set_gate(). It is just a copy of original idt table. - Register the new handlers for tracpoints to the new IDT by introducing macros to alloc_intr_gate() called at registering time of irq_vector handlers. - Add checking, whether irq vector tracing is on/off, into load_current_idt(). This has to be done below debug checking for these reasons. - Switching to debug IDT may be kicked while tracing is enabled. - On the other hands, switching to trace IDT is kicked only when debugging is disabled. In addition, the new IDT is created only when CONFIG_TRACING is enabled to avoid being used for other purposes. Signed-off-by: Seiji Aguchi Link: http://lkml.kernel.org/r/51C323ED.5050708@hds.com Signed-off-by: H. Peter Anvin Cc: Steven Rostedt

x86, trace: Introduce entering/exiting_irq()

2013-06-21T05:25:01+00:00

When implementing tracepoints in interrupt handers, if the tracepoints are simply added in the performance sensitive path of interrupt handers, it may cause potential performance problem due to the time penalty. To solve the problem, an idea is to prepare non-trace/trace irq handers and switch their IDTs at the enabling/disabling time. So, let's introduce entering_irq()/exiting_irq() for pre/post- processing of each irq handler. A way to use them is as follows. Non-trace irq handler: smp_irq_handler() { entering_irq(); /* pre-processing of this handler */ __smp_irq_handler(); /* * common logic between non-trace and trace handlers * in a vector. */ exiting_irq(); /* post-processing of this handler */ } Trace irq_handler: smp_trace_irq_handler() { entering_irq(); /* pre-processing of this handler */ trace_irq_entry(); /* tracepoint for irq entry */ __smp_irq_handler(); /* * common logic between non-trace and trace handlers * in a vector. */ trace_irq_exit(); /* tracepoint for irq exit */ exiting_irq(); /* post-processing of this handler */ } If tracepoints can place outside entering_irq()/exiting_irq() as follows, it looks cleaner. smp_trace_irq_handler() { trace_irq_entry(); smp_irq_handler(); trace_irq_exit(); } But it doesn't work. The problem is with irq_enter/exit() being called. They must be called before trace_irq_enter/exit(), because of the rcu_irq_enter() must be called before any tracepoints are used, as tracepoints use rcu to synchronize. As a possible alternative, we may be able to call irq_enter() first as follows if irq_enter() can nest. smp_trace_irq_hander() { irq_entry(); trace_irq_entry(); smp_irq_handler(); trace_irq_exit(); irq_exit(); } But it doesn't work, either. If irq_enter() is nested, it may have a time penalty because it has to check if it was already called or not. The time penalty is not desired in performance sensitive paths even if it is tiny. Signed-off-by: Seiji Aguchi Link: http://lkml.kernel.org/r/51C3238D.9040706@hds.com Signed-off-by: H. Peter Anvin Cc: Steven Rostedt

x86/reboot: Update nonmi_ipi parameter

2012-05-14T09:49:38+00:00

Update the nonmi_ipi parameter to reflect the simple change instead of the previous complicated one. There should be less of a need to use it but there may still be corner cases on older hardware that stumble into NMI issues. Signed-off-by: Don Zickus Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1336761675-24296-4-git-send-email-dzickus@redhat.com Signed-off-by: Ingo Molnar

x86/reboot: Use NMI to assist in shutting down if IRQ fails

2012-05-14T09:49:37+00:00

For v3.3, I added code to use the NMI to stop other cpus in the panic case. The idea was to make sure all cpus on the system were definitely halted to help serialize the panic path to execute the rest of the code on a single cpu. The main problem it was trying to solve was how to stop a cpu that was spinning with its irqs disabled. A IPI irq would be stuck and couldn't get in there, but an NMI could. Things were great until we had another conversation about some pstore changes. Because some of the backend pstore still uses spinlocks to protect the device access, things could get ugly if a panic happened and we were stuck spinning on a lock. Now with the NMI shutting down cpus, we could assume no other cpus were running and just bust the spin lock and proceed. The counter argument was, well if you do that the backend could be in a screwed up state and you might not be able to save anything as a result. If we could have just given the cpu a little more time to finish things, we could have grabbed the spin lock cleanly and everything would have been fine. Well, how do give a cpu a 'little more time' in the panic case? For the most part you can't without spinning on the lock and even in that case, how long do you spin for? So instead of making it ugly in the pstore code, just mimic the idea that stop_machine had, which is block on an IRQ IPI until the remote cpu has re-enabled interrupts and left the critical region. Which is what happens now using REBOOT_IRQ. Then leave the NMI case for those cpus that are truly stuck after a short time. This leaves the current behaviour alone and just handle a corner case. Most systems should never have to enter the NMI code and if they do, print out a message in case the NMI itself causes another issue. Signed-off-by: Don Zickus Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1336761675-24296-3-git-send-email-dzickus@redhat.com Signed-off-by: Ingo Molnar

Revert "x86, reboot: Use NMI instead of REBOOT_VECTOR to stop cpus"

2012-05-14T09:49:37+00:00

This reverts commit 3603a2512f9e69dc87914ba922eb4a0812b21cd6. Originally I wanted a better hammer to shutdown cpus during panic. However, this really steps on the toes of various spinlocks in the panic path. Sometimes it is easier to wait for the IRQ to become re-enabled to indictate the cpu left the critical region and then shutdown the cpu. The next patch moves the NMI addition after the IRQ part. To make it easier to see the logic of everything, revert this patch and apply the next simpler patch. Signed-off-by: Don Zickus Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1336761675-24296-2-git-send-email-dzickus@redhat.com Signed-off-by: Ingo Molnar

x86, reboot: Fix typo in nmi reboot path

2012-01-07T11:19:37+00:00

It was brought to my attention that my x86 change to use NMI in the reboot path broke Intel Nehalem and Westmere boxes when using kexec. I realized I had mistyped the if statement in commit 3603a2512f9e69dc87914ba922eb4a0812b21cd6 and stuck the ')' in the wrong spot. Putting it in the right spot fixes kexec again. Doh. Reported-by: Yinghai Lu Cc: Linus Torvalds Signed-off-by: Don Zickus Link: http://lkml.kernel.org/r/1325866671-9797-1-git-send-email-dzickus@redhat.com Signed-off-by: Ingo Molnar