Commit 9b00ac06 authored by Anton Blanchard's avatar Anton Blanchard Committed by Benjamin Herrenschmidt
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powerpc: Remove broken and complicated kdump system reset code 



We have a lot of complicated logic that handles possible recursion between
kdump and a system reset exception. We can solve this in a much simpler
way using the same setjmp/longjmp tricks xmon does.

As a first step, this patch removes the old system reset code.

Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 58154c8c

arch/powerpc/include/asm/kexec.h

+0 −6
Original line number Diff line number Diff line
@@ -73,11 +73,6 @@ extern void kexec_smp_wait(void); /* get and clear naca physid, wait for 
					  master to copy new code to 0 */

extern int crashing_cpu;

extern void crash_send_ipi(void (*crash_ipi_callback)(struct pt_regs *));

extern cpumask_t cpus_in_sr;

static inline int kexec_sr_activated(int cpu)

{

	return cpumask_test_cpu(cpu, &cpus_in_sr);

}



struct kimage;

struct pt_regs;
@@ -94,7 +89,6 @@ extern void reserve_crashkernel(void); 
extern void machine_kexec_mask_interrupts(void);



#else /* !CONFIG_KEXEC */

static inline int kexec_sr_activated(int cpu) { return 0; }

static inline void crash_kexec_secondary(struct pt_regs *regs) { }



static inline int overlaps_crashkernel(unsigned long start, unsigned long size)

arch/powerpc/kernel/crash.c

+12 −75
Original line number Diff line number Diff line
@@ -47,7 +47,6 @@ 
/* This keeps a track of which one is crashing cpu. */

int crashing_cpu = -1;

static cpumask_t cpus_in_crash = CPU_MASK_NONE;

cpumask_t cpus_in_sr = CPU_MASK_NONE;



#define CRASH_HANDLER_MAX 3

/* NULL terminated list of shutdown handles */
@@ -55,7 +54,6 @@ static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX+1]; 
static DEFINE_SPINLOCK(crash_handlers_lock);



#ifdef CONFIG_SMP

static atomic_t enter_on_soft_reset = ATOMIC_INIT(0);



void crash_ipi_callback(struct pt_regs *regs)

{
@@ -69,24 +67,9 @@ void crash_ipi_callback(struct pt_regs *regs) 
		crash_save_cpu(regs, cpu);

	cpumask_set_cpu(cpu, &cpus_in_crash);



	/*

	 * Entered via soft-reset - could be the kdump

	 * process is invoked using soft-reset or user activated

	 * it if some CPU did not respond to an IPI.

	 * For soft-reset, the secondary CPU can enter this func

	 * twice. 1 - using IPI, and 2. soft-reset.

	 * Tell the kexec CPU that entered via soft-reset and ready

	 * to go down.

	 */

	if (cpumask_test_cpu(cpu, &cpus_in_sr)) {

		cpumask_clear_cpu(cpu, &cpus_in_sr);

		atomic_inc(&enter_on_soft_reset);

	}



	/*

	 * Starting the kdump boot.

	 * This barrier is needed to make sure that all CPUs are stopped.

	 * If not, soft-reset will be invoked to bring other CPUs.

	 */

	while (!cpumask_test_cpu(crashing_cpu, &cpus_in_crash))

		cpu_relax();
@@ -103,25 +86,14 @@ void crash_ipi_callback(struct pt_regs *regs) 
	/* NOTREACHED */

}



/*

 * Wait until all CPUs are entered via soft-reset.

 */

static void crash_soft_reset_check(int cpu)

{

	unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */



	cpumask_clear_cpu(cpu, &cpus_in_sr);

	while (atomic_read(&enter_on_soft_reset) != ncpus)

		cpu_relax();

}





static void crash_kexec_prepare_cpus(int cpu)

{

	unsigned int msecs;



	unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */



	printk(KERN_EMERG "Sending IPI to other CPUs\n");



	crash_send_ipi(crash_ipi_callback);

	smp_wmb();
@@ -131,7 +103,6 @@ static void crash_kexec_prepare_cpus(int cpu) 
	 * respond.

	 * Delay of at least 10 seconds.

	 */

	printk(KERN_EMERG "Sending IPI to other cpus...\n");

	msecs = 10000;

	while ((cpumask_weight(&cpus_in_crash) < ncpus) && (--msecs > 0)) {

		cpu_relax();
@@ -140,69 +111,36 @@ static void crash_kexec_prepare_cpus(int cpu) 


	/* Would it be better to replace the trap vector here? */



	/*

	 * FIXME: In case if we do not get all CPUs, one possibility: ask the

	 * user to do soft reset such that we get all.

	 * Soft-reset will be used until better mechanism is implemented.

	 */

	if (cpumask_weight(&cpus_in_crash) < ncpus) {

		printk(KERN_EMERG "done waiting: %d cpu(s) not responding\n",

		printk(KERN_EMERG "ERROR: %d CPU(s) not responding\n",

			ncpus - cpumask_weight(&cpus_in_crash));

		printk(KERN_EMERG "Activate soft-reset to stop other cpu(s)\n");

		cpumask_clear(&cpus_in_sr);

		atomic_set(&enter_on_soft_reset, 0);

		while (cpumask_weight(&cpus_in_crash) < ncpus)

			cpu_relax();

	}

	/*

	 * Make sure all CPUs are entered via soft-reset if the kdump is

	 * invoked using soft-reset.

	 */

	if (cpumask_test_cpu(cpu, &cpus_in_sr))

		crash_soft_reset_check(cpu);

	/* Leave the IPI callback set */



	printk(KERN_EMERG "IPI complete\n");

}



/*

 * This function will be called by secondary cpus or by kexec cpu

 * if soft-reset is activated to stop some CPUs.

 * This function will be called by secondary cpus.

 */

void crash_kexec_secondary(struct pt_regs *regs)

{

	int cpu = smp_processor_id();

	unsigned long flags;

	int msecs = 5;

	int msecs = 500;



	local_irq_save(flags);

	/* Wait 5ms if the kexec CPU is not entered yet. */



	/* Wait 500ms for the primary crash CPU to signal its progress */

	while (crashing_cpu < 0) {

		if (--msecs < 0) {

			/*

			 * Either kdump image is not loaded or

			 * kdump process is not started - Probably xmon

			 * exited using 'x'(exit and recover) or

			 * kexec_should_crash() failed for all running tasks.

			 */

			cpumask_clear_cpu(cpu, &cpus_in_sr);

			/* No response, kdump image may not have been loaded */

			local_irq_restore(flags);

			return;

		}



		mdelay(1);

		cpu_relax();

	}

	if (cpu == crashing_cpu) {

		/*

		 * Panic CPU will enter this func only via soft-reset.

		 * Wait until all secondary CPUs entered and

		 * then start kexec boot.

		 */

		crash_soft_reset_check(cpu);

		cpumask_set_cpu(crashing_cpu, &cpus_in_crash);

		if (ppc_md.kexec_cpu_down)

			ppc_md.kexec_cpu_down(1, 0);

		machine_kexec(kexec_crash_image);

		/* NOTREACHED */

	}



	crash_ipi_callback(regs);

}
@@ -225,7 +163,6 @@ static void crash_kexec_prepare_cpus(int cpu) 


void crash_kexec_secondary(struct pt_regs *regs)

{

	cpumask_clear(&cpus_in_sr);

}

#endif	/* CONFIG_SMP */

arch/powerpc/kernel/traps.c

+13 −20
Original line number Diff line number Diff line
@@ -162,10 +162,20 @@ int die(const char *str, struct pt_regs *regs, long err) 
	printk("\n");

	raw_spin_unlock_irqrestore(&die.lock, flags);



	if (kexec_should_crash(current) ||

		kexec_sr_activated(smp_processor_id()))

	/*

	 * A system reset (0x100) is a request to dump, so we always send

	 * it through the crashdump code.

	 */

	if (kexec_should_crash(current) || (TRAP(regs) == 0x100)) {

		crash_kexec(regs);



		/*

		 * We aren't the primary crash CPU. We need to send it

		 * to a holding pattern to avoid it ending up in the panic

		 * code.

		 */

		crash_kexec_secondary(regs);

	}



	/*

	 * While our oops output is serialised by a spinlock, output
@@ -232,25 +242,8 @@ void system_reset_exception(struct pt_regs *regs) 
			return;

	}



#ifdef CONFIG_KEXEC

	cpumask_set_cpu(smp_processor_id(), &cpus_in_sr);

#endif



	die("System Reset", regs, SIGABRT);



	/*

	 * Some CPUs when released from the debugger will execute this path.

	 * These CPUs entered the debugger via a soft-reset. If the CPU was

	 * hung before entering the debugger it will return to the hung

	 * state when exiting this function.  This causes a problem in

	 * kdump since the hung CPU(s) will not respond to the IPI sent

	 * from kdump. To prevent the problem we call crash_kexec_secondary()

	 * here. If a kdump had not been initiated or we exit the debugger

	 * with the "exit and recover" command (x) crash_kexec_secondary()

	 * will return after 5ms and the CPU returns to its previous state.

	 */

	crash_kexec_secondary(regs);



	/* Must die if the interrupt is not recoverable */

	if (!(regs->msr & MSR_RI))

		panic("Unrecoverable System Reset");