6776648952
Currently on arm there is code that checks whether it should call dump_stack() explicitly, to avoid trying to raise an NMI when the current context is not preemptible by the backtrace IPI. Similarly, the forthcoming arch/tile support uses an IPI mechanism that does not support generating an NMI to self. Accordingly, move the code that guards this case into the generic mechanism, and invoke it unconditionally whenever we want a backtrace of the current cpu. It seems plausible that in all cases, dump_stack() will generate better information than generating a stack from the NMI handler. The register state will be missing, but that state is likely not particularly helpful in any case. Or, if we think it is helpful, we should be capturing and emitting the current register state in all cases when regs == NULL is passed to nmi_cpu_backtrace(). Link: http://lkml.kernel.org/r/1472487169-14923-3-git-send-email-cmetcalf@mellanox.com Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com> Tested-by: Daniel Thompson <daniel.thompson@linaro.org> [arm] Reviewed-by: Petr Mladek <pmladek@suse.com> Acked-by: Aaron Tomlin <atomlin@redhat.com> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Russell King <linux@arm.linux.org.uk> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
102 lines
2.7 KiB
C
102 lines
2.7 KiB
C
/*
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* NMI backtrace support
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*
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* Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,
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* with the following header:
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*
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* HW NMI watchdog support
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*
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* started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
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*
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* Arch specific calls to support NMI watchdog
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*
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* Bits copied from original nmi.c file
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*/
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#include <linux/cpumask.h>
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#include <linux/delay.h>
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#include <linux/kprobes.h>
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#include <linux/nmi.h>
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#ifdef arch_trigger_cpumask_backtrace
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/* For reliability, we're prepared to waste bits here. */
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static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
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/* "in progress" flag of arch_trigger_cpumask_backtrace */
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static unsigned long backtrace_flag;
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/*
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* When raise() is called it will be passed a pointer to the
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* backtrace_mask. Architectures that call nmi_cpu_backtrace()
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* directly from their raise() functions may rely on the mask
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* they are passed being updated as a side effect of this call.
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*/
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void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
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bool exclude_self,
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void (*raise)(cpumask_t *mask))
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{
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int i, this_cpu = get_cpu();
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if (test_and_set_bit(0, &backtrace_flag)) {
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/*
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* If there is already a trigger_all_cpu_backtrace() in progress
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* (backtrace_flag == 1), don't output double cpu dump infos.
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*/
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put_cpu();
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return;
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}
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cpumask_copy(to_cpumask(backtrace_mask), mask);
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if (exclude_self)
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cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
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/*
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* Don't try to send an NMI to this cpu; it may work on some
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* architectures, but on others it may not, and we'll get
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* information at least as useful just by doing a dump_stack() here.
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* Note that nmi_cpu_backtrace(NULL) will clear the cpu bit.
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*/
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if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask)))
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nmi_cpu_backtrace(NULL);
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if (!cpumask_empty(to_cpumask(backtrace_mask))) {
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pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
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this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
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raise(to_cpumask(backtrace_mask));
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}
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/* Wait for up to 10 seconds for all CPUs to do the backtrace */
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for (i = 0; i < 10 * 1000; i++) {
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if (cpumask_empty(to_cpumask(backtrace_mask)))
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break;
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mdelay(1);
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touch_softlockup_watchdog();
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}
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/*
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* Force flush any remote buffers that might be stuck in IRQ context
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* and therefore could not run their irq_work.
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*/
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printk_nmi_flush();
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clear_bit_unlock(0, &backtrace_flag);
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put_cpu();
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}
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bool nmi_cpu_backtrace(struct pt_regs *regs)
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{
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int cpu = smp_processor_id();
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if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
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pr_warn("NMI backtrace for cpu %d\n", cpu);
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if (regs)
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show_regs(regs);
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else
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dump_stack();
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cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
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return true;
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}
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return false;
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}
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NOKPROBE_SYMBOL(nmi_cpu_backtrace);
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#endif
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