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: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

3 files changed, 25 insertions, 101 deletions

diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index f921eb121d39..209ed8ba1637 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -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)
diff --git a/arch/powerpc/kernel/crash.c b/arch/powerpc/kernel/crash.c
index d879809d5c45..3d87b205d5f5 100644
--- a/arch/powerpc/kernel/crash.c
+++ b/arch/powerpc/kernel/crash.c
@@ -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)
 {
@@ -70,23 +68,8 @@ void crash_ipi_callback(struct pt_regs *regs)
         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 */
 
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 91377870b26a..014f88f03d3f 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -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);
-        crash_kexec_secondary(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");