1 files changed, 336 insertions, 0 deletions
diff --git a/roms/skiboot/core/lock.c b/roms/skiboot/core/lock.c
new file mode 100644
index 000000000..f0ab595b1
--- /dev/null
+++ b/roms/skiboot/core/lock.c
@@ -0,0 +1,336 @@
+// SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+/*
+ * Simple spinlock
+ *
+ * Copyright 2013-2019 IBM Corp.
+ */
+
+#include <skiboot.h>
+#include <lock.h>
+#include <assert.h>
+#include <processor.h>
+#include <cpu.h>
+#include <console.h>
+#include <timebase.h>
+
+/* Set to bust locks. Note, this is initialized to true because our
+ * lock debugging code is not going to work until we have the per
+ * CPU data initialized
+ */
+bool bust_locks = true;
+
+#define LOCK_TIMEOUT_MS 5000
+
+#ifdef DEBUG_LOCKS
+
+static void __nomcount lock_error(struct lock *l, const char *reason, uint16_t err)
+{
+	fprintf(stderr, "LOCK ERROR: %s @%p (state: 0x%016llx)\n",
+		reason, l, l->lock_val);
+	op_display(OP_FATAL, OP_MOD_LOCK, err);
+
+	abort();
+}
+
+static inline void __nomcount lock_check(struct lock *l)
+{
+	if ((l->lock_val & 1) && (l->lock_val >> 32) == this_cpu()->pir)
+		lock_error(l, "Invalid recursive lock", 0);
+}
+
+static inline void __nomcount unlock_check(struct lock *l)
+{
+	if (!(l->lock_val & 1))
+		lock_error(l, "Unlocking unlocked lock", 1);
+
+	if ((l->lock_val >> 32) != this_cpu()->pir)
+		lock_error(l, "Unlocked non-owned lock", 2);
+
+	if (l->in_con_path && this_cpu()->con_suspend == 0)
+		lock_error(l, "Unlock con lock with console not suspended", 3);
+
+	if (list_empty(&this_cpu()->locks_held))
+		lock_error(l, "Releasing lock we don't hold depth", 4);
+}
+
+static inline bool __nomcount __try_lock(struct cpu_thread *cpu, struct lock *l)
+{
+	uint64_t val;
+
+	val = cpu->pir;
+	val <<= 32;
+	val |= 1;
+
+	barrier();
+	if (__cmpxchg64(&l->lock_val, 0, val) == 0) {
+		sync();
+		return true;
+	}
+	return false;
+}
+
+static inline bool lock_timeout(unsigned long start)
+{
+	/* Print warning if lock has been spinning for more than TIMEOUT_MS */
+	unsigned long wait = tb_to_msecs(mftb());
+
+	if (wait - start > LOCK_TIMEOUT_MS) {
+		/*
+		 * If the timebase is invalid, we shouldn't
+		 * throw an error. This is possible with pending HMIs
+		 * that need to recover TB.
+		 */
+		if( !(mfspr(SPR_TFMR) & SPR_TFMR_TB_VALID))
+			return false;
+		return true;
+	}
+
+	return false;
+}
+#else
+static inline void lock_check(struct lock *l) { };
+static inline void unlock_check(struct lock *l) { };
+static inline bool lock_timeout(unsigned long s) { return false; }
+#endif /* DEBUG_LOCKS */
+
+#if defined(DEADLOCK_CHECKER) && defined(DEBUG_LOCKS)
+
+static struct lock dl_lock = {
+	.lock_val = 0,
+	.in_con_path = true,
+	.owner = LOCK_CALLER
+};
+
+/* Find circular dependencies in the lock requests. */
+static __nomcount inline bool check_deadlock(void)
+{
+	uint32_t lock_owner, start, i;
+	struct cpu_thread *next_cpu;
+	struct lock *next;
+
+	next  = this_cpu()->requested_lock;
+	start = this_cpu()->pir;
+	i = 0;
+
+	while (i < cpu_max_pir) {
+
+		if (!next)
+			return false;
+
+		if (!(next->lock_val & 1) || next->in_con_path)
+			return false;
+
+		lock_owner = next->lock_val >> 32;
+
+		if (lock_owner == start)
+			return true;
+
+		next_cpu = find_cpu_by_pir_nomcount(lock_owner);
+
+		if (!next_cpu)
+			return false;
+
+		next = next_cpu->requested_lock;
+		i++;
+	}
+
+	return false;
+}
+
+static void add_lock_request(struct lock *l)
+{
+	struct cpu_thread *curr = this_cpu();
+	bool dead;
+
+	if (curr->state != cpu_state_active &&
+	    curr->state != cpu_state_os)
+		return;
+
+	/*
+	 * For deadlock detection we must keep the lock states constant
+	 * while doing the deadlock check. However we need to avoid
+	 * clashing with the stack checker, so no mcount and use an
+	 * inline implementation of the lock for the dl_lock
+	 */
+	for (;;) {
+		if (__try_lock(curr, &dl_lock))
+			break;
+		smt_lowest();
+		while (dl_lock.lock_val)
+			barrier();
+		smt_medium();
+	}
+
+	curr->requested_lock = l;
+
+	dead = check_deadlock();
+
+	lwsync();
+	dl_lock.lock_val = 0;
+
+	if (dead)
+		lock_error(l, "Deadlock detected", 0);
+}
+
+static void remove_lock_request(void)
+{
+	this_cpu()->requested_lock = NULL;
+}
+#else
+static inline void add_lock_request(struct lock *l) { };
+static inline void remove_lock_request(void) { };
+#endif /* #if defined(DEADLOCK_CHECKER) && defined(DEBUG_LOCKS) */
+
+bool lock_held_by_me(struct lock *l)
+{
+	uint64_t pir64 = this_cpu()->pir;
+
+	return l->lock_val == ((pir64 << 32) | 1);
+}
+
+bool try_lock_caller(struct lock *l, const char *owner)
+{
+	struct cpu_thread *cpu = this_cpu();
+
+	if (bust_locks)
+		return true;
+
+	if (l->in_con_path)
+		cpu->con_suspend++;
+	if (__try_lock(cpu, l)) {
+		l->owner = owner;
+
+#ifdef DEBUG_LOCKS_BACKTRACE
+		backtrace_create(l->bt_buf, LOCKS_BACKTRACE_MAX_ENTS,
+				 &l->bt_metadata);
+#endif
+
+		list_add(&cpu->locks_held, &l->list);
+		return true;
+	}
+	if (l->in_con_path)
+		cpu->con_suspend--;
+	return false;
+}
+
+void lock_caller(struct lock *l, const char *owner)
+{
+	bool timeout_warn = false;
+	unsigned long start = 0;
+
+	if (bust_locks)
+		return;
+
+	lock_check(l);
+
+	if (try_lock_caller(l, owner))
+		return;
+	add_lock_request(l);
+
+#ifdef DEBUG_LOCKS
+	/*
+	 * Ensure that we get a valid start value
+	 * as we may be handling TFMR errors and taking
+	 * a lock to do so, so timebase could be garbage
+	 */
+	if( (mfspr(SPR_TFMR) & SPR_TFMR_TB_VALID))
+		start = tb_to_msecs(mftb());
+#endif
+
+	for (;;) {
+		if (try_lock_caller(l, owner))
+			break;
+		smt_lowest();
+		while (l->lock_val)
+			barrier();
+		smt_medium();
+
+		if (start && !timeout_warn && lock_timeout(start)) {
+			/*
+			 * Holding the lock request while printing a
+			 * timeout and taking console locks can result
+			 * in deadlock fals positive if the lock owner
+			 * tries to take the console lock. So drop it.
+			 */
+			remove_lock_request();
+			prlog(PR_WARNING, "WARNING: Lock has been spinning for over %dms\n", LOCK_TIMEOUT_MS);
+			backtrace();
+			add_lock_request(l);
+			timeout_warn = true;
+		}
+	}
+
+	remove_lock_request();
+}
+
+void unlock(struct lock *l)
+{
+	struct cpu_thread *cpu = this_cpu();
+
+	if (bust_locks)
+		return;
+
+	unlock_check(l);
+
+	l->owner = NULL;
+	list_del(&l->list);
+	lwsync();
+	l->lock_val = 0;
+
+	/* WARNING: On fast reboot, we can be reset right at that
+	 * point, so the reset_lock in there cannot be in the con path
+	 */
+	if (l->in_con_path) {
+		cpu->con_suspend--;
+		if (cpu->con_suspend == 0 && cpu->con_need_flush)
+			flush_console();
+	}
+}
+
+bool lock_recursive_caller(struct lock *l, const char *caller)
+{
+	if (bust_locks)
+		return false;
+
+	if (lock_held_by_me(l))
+		return false;
+
+	lock_caller(l, caller);
+	return true;
+}
+
+void init_locks(void)
+{
+	bust_locks = false;
+}
+
+void dump_locks_list(void)
+{
+	struct lock *l;
+
+	prlog(PR_ERR, "Locks held:\n");
+	list_for_each(&this_cpu()->locks_held, l, list) {
+		prlog(PR_ERR, "  %s\n", l->owner);
+#ifdef DEBUG_LOCKS_BACKTRACE
+		backtrace_print(l->bt_buf, &l->bt_metadata, NULL, NULL, true);
+#endif
+	}
+}
+
+void drop_my_locks(bool warn)
+{
+	struct lock *l;
+
+	disable_fast_reboot("Lock corruption");
+	while((l = list_top(&this_cpu()->locks_held, struct lock, list)) != NULL) {
+		if (warn) {
+			prlog(PR_ERR, "  %s\n", l->owner);
+#ifdef DEBUG_LOCKS_BACKTRACE
+			backtrace_print(l->bt_buf, &l->bt_metadata, NULL, NULL,
+					true);
+#endif
+		}
+		unlock(l);
+	}
+}
+