Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 998 insertions, 0 deletions

diff --git a/arch/powerpc/lib/qspinlock.c b/arch/powerpc/lib/qspinlock.c
new file mode 100644
index 000000000..95ab4cdf5
--- /dev/null
+++ b/arch/powerpc/lib/qspinlock.c
@@ -0,0 +1,998 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/bug.h>
+#include <linux/compiler.h>
+#include <linux/export.h>
+#include <linux/percpu.h>
+#include <linux/processor.h>
+#include <linux/smp.h>
+#include <linux/topology.h>
+#include <linux/sched/clock.h>
+#include <asm/qspinlock.h>
+#include <asm/paravirt.h>
+#include <trace/events/lock.h>
+
+#define MAX_NODES	4
+
+struct qnode {
+	struct qnode	*next;
+	struct qspinlock *lock;
+	int		cpu;
+	u8		sleepy; /* 1 if the previous vCPU was preempted or
+				 * if the previous node was sleepy */
+	u8		locked; /* 1 if lock acquired */
+};
+
+struct qnodes {
+	int		count;
+	struct qnode nodes[MAX_NODES];
+};
+
+/* Tuning parameters */
+static int steal_spins __read_mostly = (1 << 5);
+static int remote_steal_spins __read_mostly = (1 << 2);
+#if _Q_SPIN_TRY_LOCK_STEAL == 1
+static const bool maybe_stealers = true;
+#else
+static bool maybe_stealers __read_mostly = true;
+#endif
+static int head_spins __read_mostly = (1 << 8);
+
+static bool pv_yield_owner __read_mostly = true;
+static bool pv_yield_allow_steal __read_mostly = false;
+static bool pv_spin_on_preempted_owner __read_mostly = false;
+static bool pv_sleepy_lock __read_mostly = true;
+static bool pv_sleepy_lock_sticky __read_mostly = false;
+static u64 pv_sleepy_lock_interval_ns __read_mostly = 0;
+static int pv_sleepy_lock_factor __read_mostly = 256;
+static bool pv_yield_prev __read_mostly = true;
+static bool pv_yield_sleepy_owner __read_mostly = true;
+static bool pv_prod_head __read_mostly = false;
+
+static DEFINE_PER_CPU_ALIGNED(struct qnodes, qnodes);
+static DEFINE_PER_CPU_ALIGNED(u64, sleepy_lock_seen_clock);
+
+#if _Q_SPIN_SPEC_BARRIER == 1
+#define spec_barrier() do { asm volatile("ori 31,31,0" ::: "memory"); } while (0)
+#else
+#define spec_barrier() do { } while (0)
+#endif
+
+static __always_inline bool recently_sleepy(void)
+{
+	/* pv_sleepy_lock is true when this is called */
+	if (pv_sleepy_lock_interval_ns) {
+		u64 seen = this_cpu_read(sleepy_lock_seen_clock);
+
+		if (seen) {
+			u64 delta = sched_clock() - seen;
+			if (delta < pv_sleepy_lock_interval_ns)
+				return true;
+			this_cpu_write(sleepy_lock_seen_clock, 0);
+		}
+	}
+
+	return false;
+}
+
+static __always_inline int get_steal_spins(bool paravirt, bool sleepy)
+{
+	if (paravirt && sleepy)
+		return steal_spins * pv_sleepy_lock_factor;
+	else
+		return steal_spins;
+}
+
+static __always_inline int get_remote_steal_spins(bool paravirt, bool sleepy)
+{
+	if (paravirt && sleepy)
+		return remote_steal_spins * pv_sleepy_lock_factor;
+	else
+		return remote_steal_spins;
+}
+
+static __always_inline int get_head_spins(bool paravirt, bool sleepy)
+{
+	if (paravirt && sleepy)
+		return head_spins * pv_sleepy_lock_factor;
+	else
+		return head_spins;
+}
+
+static inline u32 encode_tail_cpu(int cpu)
+{
+	return (cpu + 1) << _Q_TAIL_CPU_OFFSET;
+}
+
+static inline int decode_tail_cpu(u32 val)
+{
+	return (val >> _Q_TAIL_CPU_OFFSET) - 1;
+}
+
+static inline int get_owner_cpu(u32 val)
+{
+	return (val & _Q_OWNER_CPU_MASK) >> _Q_OWNER_CPU_OFFSET;
+}
+
+/*
+ * Try to acquire the lock if it was not already locked. If the tail matches
+ * mytail then clear it, otherwise leave it unchnaged. Return previous value.
+ *
+ * This is used by the head of the queue to acquire the lock and clean up
+ * its tail if it was the last one queued.
+ */
+static __always_inline u32 trylock_clean_tail(struct qspinlock *lock, u32 tail)
+{
+	u32 newval = queued_spin_encode_locked_val();
+	u32 prev, tmp;
+
+	asm volatile(
+"1:	lwarx	%0,0,%2,%7	# trylock_clean_tail			\n"
+	/* This test is necessary if there could be stealers */
+"	andi.	%1,%0,%5						\n"
+"	bne	3f							\n"
+	/* Test whether the lock tail == mytail */
+"	and	%1,%0,%6						\n"
+"	cmpw	0,%1,%3							\n"
+	/* Merge the new locked value */
+"	or	%1,%1,%4						\n"
+"	bne	2f							\n"
+	/* If the lock tail matched, then clear it, otherwise leave it. */
+"	andc	%1,%1,%6						\n"
+"2:	stwcx.	%1,0,%2							\n"
+"	bne-	1b							\n"
+"\t"	PPC_ACQUIRE_BARRIER "						\n"
+"3:									\n"
+	: "=&r" (prev), "=&r" (tmp)
+	: "r" (&lock->val), "r"(tail), "r" (newval),
+	  "i" (_Q_LOCKED_VAL),
+	  "r" (_Q_TAIL_CPU_MASK),
+	  "i" (_Q_SPIN_EH_HINT)
+	: "cr0", "memory");
+
+	return prev;
+}
+
+/*
+ * Publish our tail, replacing previous tail. Return previous value.
+ *
+ * This provides a release barrier for publishing node, this pairs with the
+ * acquire barrier in get_tail_qnode() when the next CPU finds this tail
+ * value.
+ */
+static __always_inline u32 publish_tail_cpu(struct qspinlock *lock, u32 tail)
+{
+	u32 prev, tmp;
+
+	kcsan_release();
+
+	asm volatile(
+"\t"	PPC_RELEASE_BARRIER "						\n"
+"1:	lwarx	%0,0,%2		# publish_tail_cpu			\n"
+"	andc	%1,%0,%4						\n"
+"	or	%1,%1,%3						\n"
+"	stwcx.	%1,0,%2							\n"
+"	bne-	1b							\n"
+	: "=&r" (prev), "=&r"(tmp)
+	: "r" (&lock->val), "r" (tail), "r"(_Q_TAIL_CPU_MASK)
+	: "cr0", "memory");
+
+	return prev;
+}
+
+static __always_inline u32 set_mustq(struct qspinlock *lock)
+{
+	u32 prev;
+
+	asm volatile(
+"1:	lwarx	%0,0,%1		# set_mustq				\n"
+"	or	%0,%0,%2						\n"
+"	stwcx.	%0,0,%1							\n"
+"	bne-	1b							\n"
+	: "=&r" (prev)
+	: "r" (&lock->val), "r" (_Q_MUST_Q_VAL)
+	: "cr0", "memory");
+
+	return prev;
+}
+
+static __always_inline u32 clear_mustq(struct qspinlock *lock)
+{
+	u32 prev;
+
+	asm volatile(
+"1:	lwarx	%0,0,%1		# clear_mustq				\n"
+"	andc	%0,%0,%2						\n"
+"	stwcx.	%0,0,%1							\n"
+"	bne-	1b							\n"
+	: "=&r" (prev)
+	: "r" (&lock->val), "r" (_Q_MUST_Q_VAL)
+	: "cr0", "memory");
+
+	return prev;
+}
+
+static __always_inline bool try_set_sleepy(struct qspinlock *lock, u32 old)
+{
+	u32 prev;
+	u32 new = old | _Q_SLEEPY_VAL;
+
+	BUG_ON(!(old & _Q_LOCKED_VAL));
+	BUG_ON(old & _Q_SLEEPY_VAL);
+
+	asm volatile(
+"1:	lwarx	%0,0,%1		# try_set_sleepy			\n"
+"	cmpw	0,%0,%2							\n"
+"	bne-	2f							\n"
+"	stwcx.	%3,0,%1							\n"
+"	bne-	1b							\n"
+"2:									\n"
+	: "=&r" (prev)
+	: "r" (&lock->val), "r"(old), "r" (new)
+	: "cr0", "memory");
+
+	return likely(prev == old);
+}
+
+static __always_inline void seen_sleepy_owner(struct qspinlock *lock, u32 val)
+{
+	if (pv_sleepy_lock) {
+		if (pv_sleepy_lock_interval_ns)
+			this_cpu_write(sleepy_lock_seen_clock, sched_clock());
+		if (!(val & _Q_SLEEPY_VAL))
+			try_set_sleepy(lock, val);
+	}
+}
+
+static __always_inline void seen_sleepy_lock(void)
+{
+	if (pv_sleepy_lock && pv_sleepy_lock_interval_ns)
+		this_cpu_write(sleepy_lock_seen_clock, sched_clock());
+}
+
+static __always_inline void seen_sleepy_node(void)
+{
+	if (pv_sleepy_lock) {
+		if (pv_sleepy_lock_interval_ns)
+			this_cpu_write(sleepy_lock_seen_clock, sched_clock());
+		/* Don't set sleepy because we likely have a stale val */
+	}
+}
+
+static struct qnode *get_tail_qnode(struct qspinlock *lock, int prev_cpu)
+{
+	struct qnodes *qnodesp = per_cpu_ptr(&qnodes, prev_cpu);
+	int idx;
+
+	/*
+	 * After publishing the new tail and finding a previous tail in the
+	 * previous val (which is the control dependency), this barrier
+	 * orders the release barrier in publish_tail_cpu performed by the
+	 * last CPU, with subsequently looking at its qnode structures
+	 * after the barrier.
+	 */
+	smp_acquire__after_ctrl_dep();
+
+	for (idx = 0; idx < MAX_NODES; idx++) {
+		struct qnode *qnode = &qnodesp->nodes[idx];
+		if (qnode->lock == lock)
+			return qnode;
+	}
+
+	BUG();
+}
+
+/* Called inside spin_begin(). Returns whether or not the vCPU was preempted. */
+static __always_inline bool __yield_to_locked_owner(struct qspinlock *lock, u32 val, bool paravirt, bool mustq)
+{
+	int owner;
+	u32 yield_count;
+	bool preempted = false;
+
+	BUG_ON(!(val & _Q_LOCKED_VAL));
+
+	if (!paravirt)
+		goto relax;
+
+	if (!pv_yield_owner)
+		goto relax;
+
+	owner = get_owner_cpu(val);
+	yield_count = yield_count_of(owner);
+
+	if ((yield_count & 1) == 0)
+		goto relax; /* owner vcpu is running */
+
+	spin_end();
+
+	seen_sleepy_owner(lock, val);
+	preempted = true;
+
+	/*
+	 * Read the lock word after sampling the yield count. On the other side
+	 * there may a wmb because the yield count update is done by the
+	 * hypervisor preemption and the value update by the OS, however this
+	 * ordering might reduce the chance of out of order accesses and
+	 * improve the heuristic.
+	 */
+	smp_rmb();
+
+	if (READ_ONCE(lock->val) == val) {
+		if (mustq)
+			clear_mustq(lock);
+		yield_to_preempted(owner, yield_count);
+		if (mustq)
+			set_mustq(lock);
+		spin_begin();
+
+		/* Don't relax if we yielded. Maybe we should? */
+		return preempted;
+	}
+	spin_begin();
+relax:
+	spin_cpu_relax();
+
+	return preempted;
+}
+
+/* Called inside spin_begin(). Returns whether or not the vCPU was preempted. */
+static __always_inline bool yield_to_locked_owner(struct qspinlock *lock, u32 val, bool paravirt)
+{
+	return __yield_to_locked_owner(lock, val, paravirt, false);
+}
+
+/* Called inside spin_begin(). Returns whether or not the vCPU was preempted. */
+static __always_inline bool yield_head_to_locked_owner(struct qspinlock *lock, u32 val, bool paravirt)
+{
+	bool mustq = false;
+
+	if ((val & _Q_MUST_Q_VAL) && pv_yield_allow_steal)
+		mustq = true;
+
+	return __yield_to_locked_owner(lock, val, paravirt, mustq);
+}
+
+static __always_inline void propagate_sleepy(struct qnode *node, u32 val, bool paravirt)
+{
+	struct qnode *next;
+	int owner;
+
+	if (!paravirt)
+		return;
+	if (!pv_yield_sleepy_owner)
+		return;
+
+	next = READ_ONCE(node->next);
+	if (!next)
+		return;
+
+	if (next->sleepy)
+		return;
+
+	owner = get_owner_cpu(val);
+	if (vcpu_is_preempted(owner))
+		next->sleepy = 1;
+}
+
+/* Called inside spin_begin() */
+static __always_inline bool yield_to_prev(struct qspinlock *lock, struct qnode *node, int prev_cpu, bool paravirt)
+{
+	u32 yield_count;
+	bool preempted = false;
+
+	if (!paravirt)
+		goto relax;
+
+	if (!pv_yield_sleepy_owner)
+		goto yield_prev;
+
+	/*
+	 * If the previous waiter was preempted it might not be able to
+	 * propagate sleepy to us, so check the lock in that case too.
+	 */
+	if (node->sleepy || vcpu_is_preempted(prev_cpu)) {
+		u32 val = READ_ONCE(lock->val);
+
+		if (val & _Q_LOCKED_VAL) {
+			if (node->next && !node->next->sleepy) {
+				/*
+				 * Propagate sleepy to next waiter. Only if
+				 * owner is preempted, which allows the queue
+				 * to become "non-sleepy" if vCPU preemption
+				 * ceases to occur, even if the lock remains
+				 * highly contended.
+				 */
+				if (vcpu_is_preempted(get_owner_cpu(val)))
+					node->next->sleepy = 1;
+			}
+
+			preempted = yield_to_locked_owner(lock, val, paravirt);
+			if (preempted)
+				return preempted;
+		}
+		node->sleepy = false;
+	}
+
+yield_prev:
+	if (!pv_yield_prev)
+		goto relax;
+
+	yield_count = yield_count_of(prev_cpu);
+	if ((yield_count & 1) == 0)
+		goto relax; /* owner vcpu is running */
+
+	spin_end();
+
+	preempted = true;
+	seen_sleepy_node();
+
+	smp_rmb(); /* See __yield_to_locked_owner comment */
+
+	if (!READ_ONCE(node->locked)) {
+		yield_to_preempted(prev_cpu, yield_count);
+		spin_begin();
+		return preempted;
+	}
+	spin_begin();
+
+relax:
+	spin_cpu_relax();
+
+	return preempted;
+}
+
+static __always_inline bool steal_break(u32 val, int iters, bool paravirt, bool sleepy)
+{
+	if (iters >= get_steal_spins(paravirt, sleepy))
+		return true;
+
+	if (IS_ENABLED(CONFIG_NUMA) &&
+	    (iters >= get_remote_steal_spins(paravirt, sleepy))) {
+		int cpu = get_owner_cpu(val);
+		if (numa_node_id() != cpu_to_node(cpu))
+			return true;
+	}
+	return false;
+}
+
+static __always_inline bool try_to_steal_lock(struct qspinlock *lock, bool paravirt)
+{
+	bool seen_preempted = false;
+	bool sleepy = false;
+	int iters = 0;
+	u32 val;
+
+	if (!steal_spins) {
+		/* XXX: should spin_on_preempted_owner do anything here? */
+		return false;
+	}
+
+	/* Attempt to steal the lock */
+	spin_begin();
+	do {
+		bool preempted = false;
+
+		val = READ_ONCE(lock->val);
+		if (val & _Q_MUST_Q_VAL)
+			break;
+		spec_barrier();
+
+		if (unlikely(!(val & _Q_LOCKED_VAL))) {
+			spin_end();
+			if (__queued_spin_trylock_steal(lock))
+				return true;
+			spin_begin();
+		} else {
+			preempted = yield_to_locked_owner(lock, val, paravirt);
+		}
+
+		if (paravirt && pv_sleepy_lock) {
+			if (!sleepy) {
+				if (val & _Q_SLEEPY_VAL) {
+					seen_sleepy_lock();
+					sleepy = true;
+				} else if (recently_sleepy()) {
+					sleepy = true;
+				}
+			}
+			if (pv_sleepy_lock_sticky && seen_preempted &&
+			    !(val & _Q_SLEEPY_VAL)) {
+				if (try_set_sleepy(lock, val))
+					val |= _Q_SLEEPY_VAL;
+			}
+		}
+
+		if (preempted) {
+			seen_preempted = true;
+			sleepy = true;
+			if (!pv_spin_on_preempted_owner)
+				iters++;
+			/*
+			 * pv_spin_on_preempted_owner don't increase iters
+			 * while the owner is preempted -- we won't interfere
+			 * with it by definition. This could introduce some
+			 * latency issue if we continually observe preempted
+			 * owners, but hopefully that's a rare corner case of
+			 * a badly oversubscribed system.
+			 */
+		} else {
+			iters++;
+		}
+	} while (!steal_break(val, iters, paravirt, sleepy));
+
+	spin_end();
+
+	return false;
+}
+
+static __always_inline void queued_spin_lock_mcs_queue(struct qspinlock *lock, bool paravirt)
+{
+	struct qnodes *qnodesp;
+	struct qnode *next, *node;
+	u32 val, old, tail;
+	bool seen_preempted = false;
+	bool sleepy = false;
+	bool mustq = false;
+	int idx;
+	int iters = 0;
+
+	BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS));
+
+	qnodesp = this_cpu_ptr(&qnodes);
+	if (unlikely(qnodesp->count >= MAX_NODES)) {
+		spec_barrier();
+		while (!queued_spin_trylock(lock))
+			cpu_relax();
+		return;
+	}
+
+	idx = qnodesp->count++;
+	/*
+	 * Ensure that we increment the head node->count before initialising
+	 * the actual node. If the compiler is kind enough to reorder these
+	 * stores, then an IRQ could overwrite our assignments.
+	 */
+	barrier();
+	node = &qnodesp->nodes[idx];
+	node->next = NULL;
+	node->lock = lock;
+	node->cpu = smp_processor_id();
+	node->sleepy = 0;
+	node->locked = 0;
+
+	tail = encode_tail_cpu(node->cpu);
+
+	/*
+	 * Assign all attributes of a node before it can be published.
+	 * Issues an lwsync, serving as a release barrier, as well as a
+	 * compiler barrier.
+	 */
+	old = publish_tail_cpu(lock, tail);
+
+	/*
+	 * If there was a previous node; link it and wait until reaching the
+	 * head of the waitqueue.
+	 */
+	if (old & _Q_TAIL_CPU_MASK) {
+		int prev_cpu = decode_tail_cpu(old);
+		struct qnode *prev = get_tail_qnode(lock, prev_cpu);
+
+		/* Link @node into the waitqueue. */
+		WRITE_ONCE(prev->next, node);
+
+		/* Wait for mcs node lock to be released */
+		spin_begin();
+		while (!READ_ONCE(node->locked)) {
+			spec_barrier();
+
+			if (yield_to_prev(lock, node, prev_cpu, paravirt))
+				seen_preempted = true;
+		}
+		spec_barrier();
+		spin_end();
+
+		smp_rmb(); /* acquire barrier for the mcs lock */
+
+		/*
+		 * Generic qspinlocks have this prefetch here, but it seems
+		 * like it could cause additional line transitions because
+		 * the waiter will keep loading from it.
+		 */
+		if (_Q_SPIN_PREFETCH_NEXT) {
+			next = READ_ONCE(node->next);
+			if (next)
+				prefetchw(next);
+		}
+	}
+
+	/* We're at the head of the waitqueue, wait for the lock. */
+again:
+	spin_begin();
+	for (;;) {
+		bool preempted;
+
+		val = READ_ONCE(lock->val);
+		if (!(val & _Q_LOCKED_VAL))
+			break;
+		spec_barrier();
+
+		if (paravirt && pv_sleepy_lock && maybe_stealers) {
+			if (!sleepy) {
+				if (val & _Q_SLEEPY_VAL) {
+					seen_sleepy_lock();
+					sleepy = true;
+				} else if (recently_sleepy()) {
+					sleepy = true;
+				}
+			}
+			if (pv_sleepy_lock_sticky && seen_preempted &&
+			    !(val & _Q_SLEEPY_VAL)) {
+				if (try_set_sleepy(lock, val))
+					val |= _Q_SLEEPY_VAL;
+			}
+		}
+
+		propagate_sleepy(node, val, paravirt);
+		preempted = yield_head_to_locked_owner(lock, val, paravirt);
+		if (!maybe_stealers)
+			continue;
+
+		if (preempted)
+			seen_preempted = true;
+
+		if (paravirt && preempted) {
+			sleepy = true;
+
+			if (!pv_spin_on_preempted_owner)
+				iters++;
+		} else {
+			iters++;
+		}
+
+		if (!mustq && iters >= get_head_spins(paravirt, sleepy)) {
+			mustq = true;
+			set_mustq(lock);
+			val |= _Q_MUST_Q_VAL;
+		}
+	}
+	spec_barrier();
+	spin_end();
+
+	/* If we're the last queued, must clean up the tail. */
+	old = trylock_clean_tail(lock, tail);
+	if (unlikely(old & _Q_LOCKED_VAL)) {
+		BUG_ON(!maybe_stealers);
+		goto again; /* Can only be true if maybe_stealers. */
+	}
+
+	if ((old & _Q_TAIL_CPU_MASK) == tail)
+		goto release; /* We were the tail, no next. */
+
+	/* There is a next, must wait for node->next != NULL (MCS protocol) */
+	next = READ_ONCE(node->next);
+	if (!next) {
+		spin_begin();
+		while (!(next = READ_ONCE(node->next)))
+			cpu_relax();
+		spin_end();
+	}
+	spec_barrier();
+
+	/*
+	 * Unlock the next mcs waiter node. Release barrier is not required
+	 * here because the acquirer is only accessing the lock word, and
+	 * the acquire barrier we took the lock with orders that update vs
+	 * this store to locked. The corresponding barrier is the smp_rmb()
+	 * acquire barrier for mcs lock, above.
+	 */
+	if (paravirt && pv_prod_head) {
+		int next_cpu = next->cpu;
+		WRITE_ONCE(next->locked, 1);
+		if (_Q_SPIN_MISO)
+			asm volatile("miso" ::: "memory");
+		if (vcpu_is_preempted(next_cpu))
+			prod_cpu(next_cpu);
+	} else {
+		WRITE_ONCE(next->locked, 1);
+		if (_Q_SPIN_MISO)
+			asm volatile("miso" ::: "memory");
+	}
+
+release:
+	/*
+	 * Clear the lock before releasing the node, as another CPU might see stale
+	 * values if an interrupt occurs after we increment qnodesp->count
+	 * but before node->lock is initialized. The barrier ensures that
+	 * there are no further stores to the node after it has been released.
+	 */
+	node->lock = NULL;
+	barrier();
+	qnodesp->count--;
+}
+
+void __lockfunc queued_spin_lock_slowpath(struct qspinlock *lock)
+{
+	trace_contention_begin(lock, LCB_F_SPIN);
+	/*
+	 * This looks funny, but it induces the compiler to inline both
+	 * sides of the branch rather than share code as when the condition
+	 * is passed as the paravirt argument to the functions.
+	 */
+	if (IS_ENABLED(CONFIG_PARAVIRT_SPINLOCKS) && is_shared_processor()) {
+		if (try_to_steal_lock(lock, true))
+			spec_barrier();
+		else
+			queued_spin_lock_mcs_queue(lock, true);
+	} else {
+		if (try_to_steal_lock(lock, false))
+			spec_barrier();
+		else
+			queued_spin_lock_mcs_queue(lock, false);
+	}
+	trace_contention_end(lock, 0);
+}
+EXPORT_SYMBOL(queued_spin_lock_slowpath);
+
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+void pv_spinlocks_init(void)
+{
+}
+#endif
+
+#include <linux/debugfs.h>
+static int steal_spins_set(void *data, u64 val)
+{
+#if _Q_SPIN_TRY_LOCK_STEAL == 1
+	/* MAYBE_STEAL remains true */
+	steal_spins = val;
+#else
+	static DEFINE_MUTEX(lock);
+
+	/*
+	 * The lock slow path has a !maybe_stealers case that can assume
+	 * the head of queue will not see concurrent waiters. That waiter
+	 * is unsafe in the presence of stealers, so must keep them away
+	 * from one another.
+	 */
+
+	mutex_lock(&lock);
+	if (val && !steal_spins) {
+		maybe_stealers = true;
+		/* wait for queue head waiter to go away */
+		synchronize_rcu();
+		steal_spins = val;
+	} else if (!val && steal_spins) {
+		steal_spins = val;
+		/* wait for all possible stealers to go away */
+		synchronize_rcu();
+		maybe_stealers = false;
+	} else {
+		steal_spins = val;
+	}
+	mutex_unlock(&lock);
+#endif
+
+	return 0;
+}
+
+static int steal_spins_get(void *data, u64 *val)
+{
+	*val = steal_spins;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_steal_spins, steal_spins_get, steal_spins_set, "%llu\n");
+
+static int remote_steal_spins_set(void *data, u64 val)
+{
+	remote_steal_spins = val;
+
+	return 0;
+}
+
+static int remote_steal_spins_get(void *data, u64 *val)
+{
+	*val = remote_steal_spins;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_remote_steal_spins, remote_steal_spins_get, remote_steal_spins_set, "%llu\n");
+
+static int head_spins_set(void *data, u64 val)
+{
+	head_spins = val;
+
+	return 0;
+}
+
+static int head_spins_get(void *data, u64 *val)
+{
+	*val = head_spins;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_head_spins, head_spins_get, head_spins_set, "%llu\n");
+
+static int pv_yield_owner_set(void *data, u64 val)
+{
+	pv_yield_owner = !!val;
+
+	return 0;
+}
+
+static int pv_yield_owner_get(void *data, u64 *val)
+{
+	*val = pv_yield_owner;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_pv_yield_owner, pv_yield_owner_get, pv_yield_owner_set, "%llu\n");
+
+static int pv_yield_allow_steal_set(void *data, u64 val)
+{
+	pv_yield_allow_steal = !!val;
+
+	return 0;
+}
+
+static int pv_yield_allow_steal_get(void *data, u64 *val)
+{
+	*val = pv_yield_allow_steal;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_pv_yield_allow_steal, pv_yield_allow_steal_get, pv_yield_allow_steal_set, "%llu\n");
+
+static int pv_spin_on_preempted_owner_set(void *data, u64 val)
+{
+	pv_spin_on_preempted_owner = !!val;
+
+	return 0;
+}
+
+static int pv_spin_on_preempted_owner_get(void *data, u64 *val)
+{
+	*val = pv_spin_on_preempted_owner;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_pv_spin_on_preempted_owner, pv_spin_on_preempted_owner_get, pv_spin_on_preempted_owner_set, "%llu\n");
+
+static int pv_sleepy_lock_set(void *data, u64 val)
+{
+	pv_sleepy_lock = !!val;
+
+	return 0;
+}
+
+static int pv_sleepy_lock_get(void *data, u64 *val)
+{
+	*val = pv_sleepy_lock;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_pv_sleepy_lock, pv_sleepy_lock_get, pv_sleepy_lock_set, "%llu\n");
+
+static int pv_sleepy_lock_sticky_set(void *data, u64 val)
+{
+	pv_sleepy_lock_sticky = !!val;
+
+	return 0;
+}
+
+static int pv_sleepy_lock_sticky_get(void *data, u64 *val)
+{
+	*val = pv_sleepy_lock_sticky;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_pv_sleepy_lock_sticky, pv_sleepy_lock_sticky_get, pv_sleepy_lock_sticky_set, "%llu\n");
+
+static int pv_sleepy_lock_interval_ns_set(void *data, u64 val)
+{
+	pv_sleepy_lock_interval_ns = val;
+
+	return 0;
+}
+
+static int pv_sleepy_lock_interval_ns_get(void *data, u64 *val)
+{
+	*val = pv_sleepy_lock_interval_ns;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_pv_sleepy_lock_interval_ns, pv_sleepy_lock_interval_ns_get, pv_sleepy_lock_interval_ns_set, "%llu\n");
+
+static int pv_sleepy_lock_factor_set(void *data, u64 val)
+{
+	pv_sleepy_lock_factor = val;
+
+	return 0;
+}
+
+static int pv_sleepy_lock_factor_get(void *data, u64 *val)
+{
+	*val = pv_sleepy_lock_factor;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_pv_sleepy_lock_factor, pv_sleepy_lock_factor_get, pv_sleepy_lock_factor_set, "%llu\n");
+
+static int pv_yield_prev_set(void *data, u64 val)
+{
+	pv_yield_prev = !!val;
+
+	return 0;
+}
+
+static int pv_yield_prev_get(void *data, u64 *val)
+{
+	*val = pv_yield_prev;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_pv_yield_prev, pv_yield_prev_get, pv_yield_prev_set, "%llu\n");
+
+static int pv_yield_sleepy_owner_set(void *data, u64 val)
+{
+	pv_yield_sleepy_owner = !!val;
+
+	return 0;
+}
+
+static int pv_yield_sleepy_owner_get(void *data, u64 *val)
+{
+	*val = pv_yield_sleepy_owner;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_pv_yield_sleepy_owner, pv_yield_sleepy_owner_get, pv_yield_sleepy_owner_set, "%llu\n");
+
+static int pv_prod_head_set(void *data, u64 val)
+{
+	pv_prod_head = !!val;
+
+	return 0;
+}
+
+static int pv_prod_head_get(void *data, u64 *val)
+{
+	*val = pv_prod_head;
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_pv_prod_head, pv_prod_head_get, pv_prod_head_set, "%llu\n");
+
+static __init int spinlock_debugfs_init(void)
+{
+	debugfs_create_file("qspl_steal_spins", 0600, arch_debugfs_dir, NULL, &fops_steal_spins);
+	debugfs_create_file("qspl_remote_steal_spins", 0600, arch_debugfs_dir, NULL, &fops_remote_steal_spins);
+	debugfs_create_file("qspl_head_spins", 0600, arch_debugfs_dir, NULL, &fops_head_spins);
+	if (is_shared_processor()) {
+		debugfs_create_file("qspl_pv_yield_owner", 0600, arch_debugfs_dir, NULL, &fops_pv_yield_owner);
+		debugfs_create_file("qspl_pv_yield_allow_steal", 0600, arch_debugfs_dir, NULL, &fops_pv_yield_allow_steal);
+		debugfs_create_file("qspl_pv_spin_on_preempted_owner", 0600, arch_debugfs_dir, NULL, &fops_pv_spin_on_preempted_owner);
+		debugfs_create_file("qspl_pv_sleepy_lock", 0600, arch_debugfs_dir, NULL, &fops_pv_sleepy_lock);
+		debugfs_create_file("qspl_pv_sleepy_lock_sticky", 0600, arch_debugfs_dir, NULL, &fops_pv_sleepy_lock_sticky);
+		debugfs_create_file("qspl_pv_sleepy_lock_interval_ns", 0600, arch_debugfs_dir, NULL, &fops_pv_sleepy_lock_interval_ns);
+		debugfs_create_file("qspl_pv_sleepy_lock_factor", 0600, arch_debugfs_dir, NULL, &fops_pv_sleepy_lock_factor);
+		debugfs_create_file("qspl_pv_yield_prev", 0600, arch_debugfs_dir, NULL, &fops_pv_yield_prev);
+		debugfs_create_file("qspl_pv_yield_sleepy_owner", 0600, arch_debugfs_dir, NULL, &fops_pv_yield_sleepy_owner);
+		debugfs_create_file("qspl_pv_prod_head", 0600, arch_debugfs_dir, NULL, &fops_pv_prod_head);
+	}
+
+	return 0;
+}
+device_initcall(spinlock_debugfs_init);