Merge tag 'locking-core-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Ingo Molnar:
 "Core locking primitives updates:
    - Remove mutex_trylock_recursive() from the API - no users left
    - Simplify + constify the futex code a bit

  Lockdep updates:
    - Teach lockdep about local_lock_t
    - Add CONFIG_DEBUG_IRQFLAGS=y debug config option to check for
      potentially unsafe IRQ mask restoration patterns. (I.e.
      calling raw_local_irq_restore() with IRQs enabled.)
    - Add wait context self-tests
    - Fix graph lock corner case corrupting internal data structures
    - Fix noinstr annotations

  LKMM updates:
    - Simplify the litmus tests
    - Documentation fixes

  KCSAN updates:
    - Re-enable KCSAN instrumentation in lib/random32.c

  Misc fixes:
    - Don't branch-trace static label APIs
    - DocBook fix
    - Remove stale leftover empty file"

* tag 'locking-core-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
  checkpatch: Don't check for mutex_trylock_recursive()
  locking/mutex: Kill mutex_trylock_recursive()
  s390: Use arch_local_irq_{save,restore}() in early boot code
  lockdep: Noinstr annotate warn_bogus_irq_restore()
  locking/lockdep: Avoid unmatched unlock
  locking/rwsem: Remove empty rwsem.h
  locking/rtmutex: Add missing kernel-doc markup
  futex: Remove unneeded gotos
  futex: Change utime parameter to be 'const ... *'
  lockdep: report broken irq restoration
  jump_label: Do not profile branch annotations
  locking: Add Reviewers
  locking/selftests: Add local_lock inversion tests
  locking/lockdep: Exclude local_lock_t from IRQ inversions
  locking/lockdep: Clean up check_redundant() a bit
  locking/lockdep: Add a skip() function to __bfs()
  locking/lockdep: Mark local_lock_t
  locking/selftests: More granular debug_locks_verbose
  lockdep/selftest: Add wait context selftests
  tools/memory-model: Fix typo in klitmus7 compatibility table
  ...

1 files changed, 13 insertions, 13 deletions

diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
index 3994a217bde7..3bf98db9c702 100644
--- a/kernel/kcsan/core.c
+++ b/kernel/kcsan/core.c
@@ -12,7 +12,6 @@
 #include <linux/moduleparam.h>
 #include <linux/percpu.h>
 #include <linux/preempt.h>
-#include <linux/random.h>
 #include <linux/sched.h>
 #include <linux/uaccess.h>
 
@@ -101,7 +100,7 @@ static atomic_long_t watchpoints[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS-1];
 static DEFINE_PER_CPU(long, kcsan_skip);
 
 /* For kcsan_prandom_u32_max(). */
-static DEFINE_PER_CPU(struct rnd_state, kcsan_rand_state);
+static DEFINE_PER_CPU(u32, kcsan_rand_state);
 
 static __always_inline atomic_long_t *find_watchpoint(unsigned long addr,
 						      size_t size,
@@ -275,20 +274,17 @@ should_watch(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *
 }
 
 /*
- * Returns a pseudo-random number in interval [0, ep_ro). See prandom_u32_max()
- * for more details.
- *
- * The open-coded version here is using only safe primitives for all contexts
- * where we can have KCSAN instrumentation. In particular, we cannot use
- * prandom_u32() directly, as its tracepoint could cause recursion.
+ * Returns a pseudo-random number in interval [0, ep_ro). Simple linear
+ * congruential generator, using constants from "Numerical Recipes".
  */
 static u32 kcsan_prandom_u32_max(u32 ep_ro)
 {
-	struct rnd_state *state = &get_cpu_var(kcsan_rand_state);
-	const u32 res = prandom_u32_state(state);
+	u32 state = this_cpu_read(kcsan_rand_state);
+
+	state = 1664525 * state + 1013904223;
+	this_cpu_write(kcsan_rand_state, state);
 
-	put_cpu_var(kcsan_rand_state);
-	return (u32)(((u64) res * ep_ro) >> 32);
+	return state % ep_ro;
 }
 
 static inline void reset_kcsan_skip(void)
@@ -639,10 +635,14 @@ static __always_inline void check_access(const volatile void *ptr, size_t size,
 
 void __init kcsan_init(void)
 {
+	int cpu;
+
 	BUG_ON(!in_task());
 
 	kcsan_debugfs_init();
-	prandom_seed_full_state(&kcsan_rand_state);
+
+	for_each_possible_cpu(cpu)
+		per_cpu(kcsan_rand_state, cpu) = (u32)get_cycles();
 
 	/*
 	 * We are in the init task, and no other tasks should be running;