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authorDaniel Thompson <daniel.thompson@linaro.org>2014-06-11 14:08:27 +0100
committerDaniel Thompson <daniel.thompson@linaro.org>2016-06-20 14:56:57 +0100
commit460b4ca23a99cf780743e8c905ac1c9ce2d8503a (patch)
tree1599b3a9f6bf1035da2043eabd8da8d3ec0e776d
parent3cacad1d6176e2f58ef647f002c690a26199bc6d (diff)
downloadlinux-460b4ca23a99cf780743e8c905ac1c9ce2d8503a.tar.gz
misc: Add a lockup driver to get the CPUs wedged
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
-rw-r--r--drivers/misc/Makefile1
-rw-r--r--drivers/misc/lockup.c169
2 files changed, 170 insertions, 0 deletions
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index b2fb6dbffcef..1301cb90c851 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -57,3 +57,4 @@ obj-$(CONFIG_ECHO) += echo/
obj-$(CONFIG_VEXPRESS_SYSCFG) += vexpress-syscfg.o
obj-$(CONFIG_CXL_BASE) += cxl/
obj-$(CONFIG_PANEL) += panel.o
+obj-y += lockup.o
diff --git a/drivers/misc/lockup.c b/drivers/misc/lockup.c
new file mode 100644
index 000000000000..8af1300cfcfe
--- /dev/null
+++ b/drivers/misc/lockup.c
@@ -0,0 +1,169 @@
+/*
+ * lockup.c
+ *
+ * Deliberately do "stupid" things to see if we can detect/debug them
+ * properly.
+ *
+ * The sole purpose of this module is to help with debugging of system
+ * debug tools.
+ *
+ * Copyright (C) 2014 Linaro Limited
+ * Daniel Thompson <daniel.thompson@linaro.org>
+ */
+
+#define pr_fmt(fmt) "lockup[%u]: " fmt, smp_processor_id()
+
+#include <linux/smp.h>
+#include <linux/debugfs.h>
+#include <linux/debug_locks.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/irq_work.h>
+
+static DEFINE_SPINLOCK(lockup_lock);
+
+static int lockup_do_action_on_cpu(int cpu, long (*action)(void *))
+{
+ if (cpu == -1)
+ (void) action(NULL);
+
+ if (cpu < 0 || cpu > num_possible_cpus())
+ return -EINVAL;
+
+ pr_info("About to run %pf on cpu %d\n", action, cpu);
+
+ /* work_on_cpu() ends up performing an uninterruptible
+ * wait-for-completion. This means we'll lose the prompt
+ * regardless of the CPU we send the work to.
+ */
+ work_on_cpu(cpu, action, NULL);
+
+ return 0;
+}
+
+#define DEFINE_LOCKUP_ATTRIBUTE(__fops, __action) \
+ static int __fops##_get(void *data, u64 *val) \
+ { \
+ *val = __action(NULL); \
+ return 0; \
+ } \
+ static int __fops##_set(void *data, u64 val) \
+ { \
+ lockup_do_action_on_cpu(val, __action); \
+ return 0; \
+ } \
+ DEFINE_SIMPLE_ATTRIBUTE(__fops, __fops##_get, __fops##_set, "%llu\n")
+
+static long do_lockup_livelock_irq(void *info)
+{
+ pr_warn("About to live lock after spin_lock_irq\n");
+ spin_lock_irq(&lockup_lock);
+ while (1)
+ cpu_relax();
+ spin_unlock_irq(&lockup_lock);
+
+ return 0;
+}
+
+DEFINE_LOCKUP_ATTRIBUTE(lockup_livelock_irq_fops, do_lockup_livelock_irq);
+
+
+static long do_lockup_spin_lock(void *info)
+{
+ pr_warn("About to wedge in spin_lock\n");
+ spin_lock(&lockup_lock);
+ debug_locks_off(); /* we plan to deadlock here */
+ spin_lock(&lockup_lock);
+ spin_unlock(&lockup_lock);
+ spin_unlock(&lockup_lock);
+ return 0;
+}
+DEFINE_LOCKUP_ATTRIBUTE(lockup_spin_lock_fops, do_lockup_spin_lock);
+
+static long do_lockup_spin_lock_irqsave(void *info)
+{
+ unsigned long flags1, flags2;
+
+ pr_warn("About to wedge in spin_lock_irqsave\n");
+ spin_lock_irqsave(&lockup_lock, flags1);
+ debug_locks_off(); /* we plan to deadlock here... */
+ spin_lock_irqsave(&lockup_lock, flags2);
+ spin_unlock_irqrestore(&lockup_lock, flags2);
+ spin_unlock_irqrestore(&lockup_lock, flags1);
+ return 0;
+}
+DEFINE_LOCKUP_ATTRIBUTE(lockup_spin_lock_irqsave_fops,
+ do_lockup_spin_lock_irqsave);
+
+static void infinite_loop_holding_a_spinlock(struct irq_work *w)
+{
+ unsigned long flags;
+
+ pr_warn("About to live lock after spin_lock_irqsave\n");
+ spin_lock_irqsave(&lockup_lock, flags);
+ while (1)
+ cpu_relax();
+ spin_unlock_irqrestore(&lockup_lock, flags);
+}
+DEFINE_IRQ_WORK(infinite_loop_holding_a_spinlock_work,
+ infinite_loop_holding_a_spinlock);
+
+static void stuck_waiting_for_spinlock(struct irq_work *w)
+{
+ unsigned long flags;
+
+ pr_warn("About to wedge in spin_lock_irqsave\n");
+ spin_lock_irqsave(&lockup_lock, flags);
+ spin_unlock_irqrestore(&lockup_lock, flags);
+}
+DEFINE_IRQ_WORK(stuck_waiting_for_spinlock_work,
+ stuck_waiting_for_spinlock);
+
+#ifdef CONFIG_SMP
+static int lockup_wedge_get(void *data, u64 *val)
+{
+ pr_info("About to run infinite_loop_holding_a_spinlock on cpu 2\n");
+ irq_work_queue_on(&infinite_loop_holding_a_spinlock_work, 2);
+ mdelay(20);
+ pr_info("About to run stuck_waiting_for_spinlock on cpu 3\n");
+ irq_work_queue_on(&stuck_waiting_for_spinlock_work, 3);
+
+ return 0;
+}
+DEFINE_SIMPLE_ATTRIBUTE(lockup_wedge_fops, lockup_wedge_get, NULL, "%llu\n");
+#endif /* CONFIG_SMP */
+
+static int __init lockup_init(void)
+{
+#define E(x) { #x, &lockup_##x##_fops }
+ const struct {
+ const char *name;
+ const struct file_operations *fops;
+ } fops_table[] = {
+ E(livelock_irq),
+ E(spin_lock),
+ E(spin_lock_irqsave),
+#ifdef CONFIG_SMP
+ E(wedge),
+#endif
+ };
+#undef E
+
+ struct dentry *dir;
+ unsigned int i;
+
+ dir = debugfs_create_dir("lockup", NULL);
+ if (dir)
+ for (i = 0; i < ARRAY_SIZE(fops_table); i++)
+ (void)debugfs_create_file(fops_table[i].name,
+ S_IRUGO | S_IWUSR, dir, NULL,
+ fops_table[i].fops);
+
+ pr_info("created attributes\n");
+ return 0;
+}
+
+module_init(lockup_init);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Daniel Thompson");