Merge tag 'rcu.release.v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

Pull RCU updates from Neeraj Upadhyay:
 "Expedited grace period updates:

   - Protect against early RCU exp quiescent state reporting during exp
     grace period initialization

   - Remove superfluous barrier in task unblock path

   - Remove the CPU online quiescent state report optimization, which is
     error prone for certain scenarios

   - Add warning for unexpected pending requested expedited quiescent
     state on dying CPU

  Core:

   - Robustify rcu_is_cpu_rrupt_from_idle() by using more accurate
     indicators of the actual context tracking state of a CPU

   - Handle ->defer_qs_iw_pending field data race

   - Enable rcu_normal_wake_from_gp by default on systems with <= 16
     CPUs

   - Fix lockup in rcu_read_unlock() due to recursive irq_exit() calls

   - Refactor expedited handling condition in rcu_read_unlock_special()

   - Documentation updates for hotplug and GP init scan ordering,
     separation of rcu_state and rnp's gp_seq states, quiescent state
     reporting for offline CPUs

  torture-scripts:

   - Cleanup and improve scripts : remove superfluous warnings for
     disabled tests; better handling of kvm.sh --kconfig arg; suppress
     some confusing diagnostics; tolerate bad kvm.sh args; add new
     diagnostic for build output; fail allmodconfig testing on warnings

   - Include RCU_TORTURE_TEST_CHK_RDR_STATE config for KCSAN kernels

   - Disable default RCU-tasks and clocksource-wdog testing on arm64

   - Add EXPERT Kconfig option for arm64 KCSAN runs

   - Remove SRCU-lite testing

  rcutorture:

   - Start torture writer threads creation after reader threads to
     handle race in SRCU-P scenario

   - Add SRCU down_read()/up_read() test

   - Add diagnostics for delayed SRCU up_read(), unmatched up_read(),
     print number of up/down readers and the number of such readers
     which migrated to other CPU

   - Ignore certain unsupported configurations for trivial RCU test

   - Fix splats in RT kernels due to inaccurate checks for BH-disabled
     context

   - Enable checks and logs to capture intentionally exercised
     unexpected scenarios (too short readers) for BUSTED test

   - Remove SRCU-lite testing

  srcu:

   - Expedite SRCU-fast grace periods

   - Remove SRCU-lite implementation

   - Add guards for SRCU-fast readers

  rcu nocb:

   - Dump NOCB group leader state on stall detection

   - Robustify nocb_cb_kthread pointer accesses

   - Fix delayed execution of hurry callbacks when LAZY_RCU is enabled

  refscale:

   - Fix multiplication overflow in "loops" and "nreaders" calculations"

* tag 'rcu.release.v6.17' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (49 commits)
  rcu: Document concurrent quiescent state reporting for offline CPUs
  rcu: Document separation of rcu_state and rnp's gp_seq
  rcu: Document GP init vs hotplug-scan ordering requirements
  srcu: Add guards for SRCU-fast readers
  rcu: Fix delayed execution of hurry callbacks
  rcu: Refactor expedited handling check in rcu_read_unlock_special()
  checkpatch: Remove SRCU-lite deprecation
  srcu: Remove SRCU-lite implementation
  srcu: Expedite SRCU-fast grace periods
  rcutorture: Remove support for SRCU-lite
  rcutorture: Remove SRCU-lite scenarios
  torture: Remove support for SRCU-lite
  torture: Make torture.sh --allmodconfig testing fail on warnings
  torture: Add "ERROR" diagnostic for testing kernel-build output
  torture: Make torture.sh tolerate runs having bad kvm.sh arguments
  torture: Add textid.txt file to --do-allmodconfig and --do-rcu-rust runs
  torture: Extract testid.txt generation to separate script
  torture: Suppress "find" diagnostics from torture.sh --do-none run
  torture: Provide EXPERT Kconfig option for arm64 KCSAN torture.sh runs
  rcu: Fix rcu_read_unlock() deadloop due to IRQ work
  ...

3 files changed, 8 insertions, 87 deletions

diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 900b0d5c05f5..f179700fecaf 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -46,11 +46,11 @@ int init_srcu_struct(struct srcu_struct *ssp);
 /* Values for SRCU Tree srcu_data ->srcu_reader_flavor, but also used by rcutorture. */
 #define SRCU_READ_FLAVOR_NORMAL	0x1		// srcu_read_lock().
 #define SRCU_READ_FLAVOR_NMI	0x2		// srcu_read_lock_nmisafe().
-#define SRCU_READ_FLAVOR_LITE	0x4		// srcu_read_lock_lite().
+//				0x4		// SRCU-lite is no longer with us.
 #define SRCU_READ_FLAVOR_FAST	0x8		// srcu_read_lock_fast().
 #define SRCU_READ_FLAVOR_ALL   (SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_NMI | \
-				SRCU_READ_FLAVOR_LITE | SRCU_READ_FLAVOR_FAST) // All of the above.
-#define SRCU_READ_FLAVOR_SLOWGP	(SRCU_READ_FLAVOR_LITE | SRCU_READ_FLAVOR_FAST)
+				SRCU_READ_FLAVOR_FAST) // All of the above.
+#define SRCU_READ_FLAVOR_SLOWGP	SRCU_READ_FLAVOR_FAST
 						// Flavors requiring synchronize_rcu()
 						// instead of smp_mb().
 void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp);
@@ -300,33 +300,6 @@ static inline struct srcu_ctr __percpu *srcu_down_read_fast(struct srcu_struct *
 }
 
 /**
- * srcu_read_lock_lite - register a new reader for an SRCU-protected structure.
- * @ssp: srcu_struct in which to register the new reader.
- *
- * Enter an SRCU read-side critical section, but for a light-weight
- * smp_mb()-free reader.  See srcu_read_lock() for more information.
- *
- * If srcu_read_lock_lite() is ever used on an srcu_struct structure,
- * then none of the other flavors may be used, whether before, during,
- * or after.  Note that grace-period auto-expediting is disabled for _lite
- * srcu_struct structures because auto-expedited grace periods invoke
- * synchronize_rcu_expedited(), IPIs and all.
- *
- * Note that srcu_read_lock_lite() can be invoked only from those contexts
- * where RCU is watching, that is, from contexts where it would be legal
- * to invoke rcu_read_lock().  Otherwise, lockdep will complain.
- */
-static inline int srcu_read_lock_lite(struct srcu_struct *ssp) __acquires(ssp)
-{
-	int retval;
-
-	srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_LITE);
-	retval = __srcu_read_lock_lite(ssp);
-	rcu_try_lock_acquire(&ssp->dep_map);
-	return retval;
-}
-
-/**
  * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected structure.
  * @ssp: srcu_struct in which to register the new reader.
  *
@@ -435,22 +408,6 @@ static inline void srcu_up_read_fast(struct srcu_struct *ssp, struct srcu_ctr __
 }
 
 /**
- * srcu_read_unlock_lite - unregister a old reader from an SRCU-protected structure.
- * @ssp: srcu_struct in which to unregister the old reader.
- * @idx: return value from corresponding srcu_read_lock_lite().
- *
- * Exit a light-weight SRCU read-side critical section.
- */
-static inline void srcu_read_unlock_lite(struct srcu_struct *ssp, int idx)
-	__releases(ssp)
-{
-	WARN_ON_ONCE(idx & ~0x1);
-	srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_LITE);
-	srcu_lock_release(&ssp->dep_map);
-	__srcu_read_unlock_lite(ssp, idx);
-}
-
-/**
  * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protected structure.
  * @ssp: srcu_struct in which to unregister the old reader.
  * @idx: return value from corresponding srcu_read_lock_nmisafe().
@@ -524,4 +481,9 @@ DEFINE_LOCK_GUARD_1(srcu, struct srcu_struct,
 		    srcu_read_unlock(_T->lock, _T->idx),
 		    int idx)
 
+DEFINE_LOCK_GUARD_1(srcu_fast, struct srcu_struct,
+		    _T->scp = srcu_read_lock_fast(_T->lock),
+		    srcu_read_unlock_fast(_T->lock, _T->scp),
+		    struct srcu_ctr __percpu *scp)
+
 #endif
diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h
index 380260317d98..51ce25f07930 100644
--- a/include/linux/srcutiny.h
+++ b/include/linux/srcutiny.h
@@ -93,9 +93,6 @@ static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_
 	__srcu_read_unlock(ssp, __srcu_ptr_to_ctr(ssp, scp));
 }
 
-#define __srcu_read_lock_lite __srcu_read_lock
-#define __srcu_read_unlock_lite __srcu_read_unlock
-
 static inline void synchronize_srcu_expedited(struct srcu_struct *ssp)
 {
 	synchronize_srcu(ssp);
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 8bed7e6cc4c1..bf44d8d1e69e 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -278,44 +278,6 @@ static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_
 	RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_fast().");
 }
 
-/*
- * Counts the new reader in the appropriate per-CPU element of the
- * srcu_struct.  Returns an index that must be passed to the matching
- * srcu_read_unlock_lite().
- *
- * Note that this_cpu_inc() is an RCU read-side critical section either
- * because it disables interrupts, because it is a single instruction,
- * or because it is a read-modify-write atomic operation, depending on
- * the whims of the architecture.
- */
-static inline int __srcu_read_lock_lite(struct srcu_struct *ssp)
-{
-	struct srcu_ctr __percpu *scp = READ_ONCE(ssp->srcu_ctrp);
-
-	RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_lite().");
-	this_cpu_inc(scp->srcu_locks.counter); /* Y */
-	barrier(); /* Avoid leaking the critical section. */
-	return __srcu_ptr_to_ctr(ssp, scp);
-}
-
-/*
- * Removes the count for the old reader from the appropriate
- * per-CPU element of the srcu_struct.  Note that this may well be a
- * different CPU than that which was incremented by the corresponding
- * srcu_read_lock_lite(), but it must be within the same task.
- *
- * Note that this_cpu_inc() is an RCU read-side critical section either
- * because it disables interrupts, because it is a single instruction,
- * or because it is a read-modify-write atomic operation, depending on
- * the whims of the architecture.
- */
-static inline void __srcu_read_unlock_lite(struct srcu_struct *ssp, int idx)
-{
-	barrier();  /* Avoid leaking the critical section. */
-	this_cpu_inc(__srcu_ctr_to_ptr(ssp, idx)->srcu_unlocks.counter);  /* Z */
-	RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_lite().");
-}
-
 void __srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor);
 
 // Record reader usage even for CONFIG_PROVE_RCU=n kernels.  This is