[PATCH] spinlock consolidation

This patch (written by me and also containing many suggestions of Arjan van
de Ven) does a major cleanup of the spinlock code.  It does the following
things:

 - consolidates and enhances the spinlock/rwlock debugging code

 - simplifies the asm/spinlock.h files

 - encapsulates the raw spinlock type and moves generic spinlock
   features (such as ->break_lock) into the generic code.

 - cleans up the spinlock code hierarchy to get rid of the spaghetti.

Most notably there's now only a single variant of the debugging code,
located in lib/spinlock_debug.c.  (previously we had one SMP debugging
variant per architecture, plus a separate generic one for UP builds)

Also, i've enhanced the rwlock debugging facility, it will now track
write-owners.  There is new spinlock-owner/CPU-tracking on SMP builds too.
All locks have lockup detection now, which will work for both soft and hard
spin/rwlock lockups.

The arch-level include files now only contain the minimally necessary
subset of the spinlock code - all the rest that can be generalized now
lives in the generic headers:

 include/asm-i386/spinlock_types.h       |   16
 include/asm-x86_64/spinlock_types.h     |   16

I have also split up the various spinlock variants into separate files,
making it easier to see which does what. The new layout is:

   SMP                         |  UP
   ----------------------------|-----------------------------------
   asm/spinlock_types_smp.h    |  linux/spinlock_types_up.h
   linux/spinlock_types.h      |  linux/spinlock_types.h
   asm/spinlock_smp.h          |  linux/spinlock_up.h
   linux/spinlock_api_smp.h    |  linux/spinlock_api_up.h
   linux/spinlock.h            |  linux/spinlock.h

/*
 * here's the role of the various spinlock/rwlock related include files:
 *
 * on SMP builds:
 *
 *  asm/spinlock_types.h: contains the raw_spinlock_t/raw_rwlock_t and the
 *                        initializers
 *
 *  linux/spinlock_types.h:
 *                        defines the generic type and initializers
 *
 *  asm/spinlock.h:       contains the __raw_spin_*()/etc. lowlevel
 *                        implementations, mostly inline assembly code
 *
 *   (also included on UP-debug builds:)
 *
 *  linux/spinlock_api_smp.h:
 *                        contains the prototypes for the _spin_*() APIs.
 *
 *  linux/spinlock.h:     builds the final spin_*() APIs.
 *
 * on UP builds:
 *
 *  linux/spinlock_type_up.h:
 *                        contains the generic, simplified UP spinlock type.
 *                        (which is an empty structure on non-debug builds)
 *
 *  linux/spinlock_types.h:
 *                        defines the generic type and initializers
 *
 *  linux/spinlock_up.h:
 *                        contains the __raw_spin_*()/etc. version of UP
 *                        builds. (which are NOPs on non-debug, non-preempt
 *                        builds)
 *
 *   (included on UP-non-debug builds:)
 *
 *  linux/spinlock_api_up.h:
 *                        builds the _spin_*() APIs.
 *
 *  linux/spinlock.h:     builds the final spin_*() APIs.
 */

All SMP and UP architectures are converted by this patch.

arm, i386, ia64, ppc, ppc64, s390/s390x, x64 was build-tested via
crosscompilers.  m32r, mips, sh, sparc, have not been tested yet, but should
be mostly fine.

From: Grant Grundler <grundler@parisc-linux.org>

  Booted and lightly tested on a500-44 (64-bit, SMP kernel, dual CPU).
  Builds 32-bit SMP kernel (not booted or tested).  I did not try to build
  non-SMP kernels.  That should be trivial to fix up later if necessary.

  I converted bit ops atomic_hash lock to raw_spinlock_t.  Doing so avoids
  some ugly nesting of linux/*.h and asm/*.h files.  Those particular locks
  are well tested and contained entirely inside arch specific code.  I do NOT
  expect any new issues to arise with them.

 If someone does ever need to use debug/metrics with them, then they will
  need to unravel this hairball between spinlocks, atomic ops, and bit ops
  that exist only because parisc has exactly one atomic instruction: LDCW
  (load and clear word).

From: "Luck, Tony" <tony.luck@intel.com>

   ia64 fix

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjanv@infradead.org>
Signed-off-by: Grant Grundler <grundler@parisc-linux.org>
Cc: Matthew Wilcox <willy@debian.org>
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Mikael Pettersson <mikpe@csd.uu.se>
Signed-off-by: Benoit Boissinot <benoit.boissinot@ens-lyon.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 2 insertions, 281 deletions

diff --git a/arch/parisc/lib/Makefile b/arch/parisc/lib/Makefile
index 7bf70567629..5f2e6904d14 100644
--- a/arch/parisc/lib/Makefile
+++ b/arch/parisc/lib/Makefile
@@ -5,5 +5,3 @@
 lib-y	:= lusercopy.o bitops.o checksum.o io.o memset.o fixup.o memcpy.o
 
 obj-y	:= iomap.o
-
-lib-$(CONFIG_SMP) += debuglocks.o
diff --git a/arch/parisc/lib/bitops.c b/arch/parisc/lib/bitops.c
index 2de182f6fe8..90f400b1028 100644
--- a/arch/parisc/lib/bitops.c
+++ b/arch/parisc/lib/bitops.c
@@ -13,8 +13,8 @@
 #include <asm/atomic.h>
 
 #ifdef CONFIG_SMP
-spinlock_t __atomic_hash[ATOMIC_HASH_SIZE] __lock_aligned = {
-	[0 ... (ATOMIC_HASH_SIZE-1)]  = SPIN_LOCK_UNLOCKED
+raw_spinlock_t __atomic_hash[ATOMIC_HASH_SIZE] __lock_aligned = {
+	[0 ... (ATOMIC_HASH_SIZE-1)]  = __RAW_SPIN_LOCK_UNLOCKED
 };
 #endif
 
diff --git a/arch/parisc/lib/debuglocks.c b/arch/parisc/lib/debuglocks.c
deleted file mode 100644
index 1b33fe6e5b7..00000000000
--- a/arch/parisc/lib/debuglocks.c
+++ /dev/null
@@ -1,277 +0,0 @@
-/* 
- *    Debugging versions of SMP locking primitives.
- *
- *    Copyright (C) 2004 Thibaut VARENE <varenet@parisc-linux.org>
- *
- *    Some code stollen from alpha & sparc64 ;)
- *
- *    This program is free software; you can redistribute it and/or modify
- *    it under the terms of the GNU General Public License as published by
- *    the Free Software Foundation; either version 2 of the License, or
- *    (at your option) any later version.
- *
- *    This program is distributed in the hope that it will be useful,
- *    but WITHOUT ANY WARRANTY; without even the implied warranty of
- *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *    GNU General Public License for more details.
- *
- *    You should have received a copy of the GNU General Public License
- *    along with this program; if not, write to the Free Software
- *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
- *
- *    We use pdc_printf() throughout the file for all output messages, to avoid
- *    losing messages because of disabled interrupts. Since we're using these
- *    messages for debugging purposes, it makes sense not to send them to the
- *    linux console.
- */
-
-
-#include <linux/config.h>
-#include <linux/kernel.h>
-#include <linux/sched.h>
-#include <linux/spinlock.h>
-#include <linux/hardirq.h>	/* in_interrupt() */
-#include <asm/system.h>
-#include <asm/hardirq.h>	/* in_interrupt() */
-#include <asm/pdc.h>
-
-#undef INIT_STUCK
-#define INIT_STUCK 1L << 30
-
-#ifdef CONFIG_DEBUG_SPINLOCK
-
-
-void _dbg_spin_lock(spinlock_t * lock, const char *base_file, int line_no)
-{
-	volatile unsigned int *a;
-	long stuck = INIT_STUCK;
-	void *inline_pc = __builtin_return_address(0);
-	unsigned long started = jiffies;
-	int printed = 0;
-	int cpu = smp_processor_id();
-
-try_again:
-
-	/* Do the actual locking */
-	/* <T-Bone> ggg: we can't get stuck on the outter loop?
-	 * <ggg> T-Bone: We can hit the outer loop
-	 *	alot if multiple CPUs are constantly racing for a lock
-	 *	and the backplane is NOT fair about which CPU sees
-	 *	the update first. But it won't hang since every failed
-	 *	attempt will drop us back into the inner loop and
-	 *	decrement `stuck'.
-	 * <ggg> K-class and some of the others are NOT fair in the HW
-	 * 	implementation so we could see false positives.
-	 * 	But fixing the lock contention is easier than
-	 * 	fixing the HW to be fair.
-	 * <tausq> __ldcw() returns 1 if we get the lock; otherwise we
-	 * 	spin until the value of the lock changes, or we time out.
-	 */
-	mb();
-	a = __ldcw_align(lock);
-	while (stuck && (__ldcw(a) == 0))
-		while ((*a == 0) && --stuck);
-	mb();
-
-	if (unlikely(stuck <= 0)) {
-		pdc_printf(
-			"%s:%d: spin_lock(%s/%p) stuck in %s at %p(%d)"
-			" owned by %s:%d in %s at %p(%d)\n",
-			base_file, line_no, lock->module, lock,
-			current->comm, inline_pc, cpu,
-			lock->bfile, lock->bline, lock->task->comm,
-			lock->previous, lock->oncpu);
-		stuck = INIT_STUCK;
-		printed = 1;
-		goto try_again;
-	}
-
-	/* Exiting.  Got the lock.  */
-	lock->oncpu = cpu;
-	lock->previous = inline_pc;
-	lock->task = current;
-	lock->bfile = (char *)base_file;
-	lock->bline = line_no;
-
-	if (unlikely(printed)) {
-		pdc_printf(
-			"%s:%d: spin_lock grabbed in %s at %p(%d) %ld ticks\n",
-			base_file, line_no, current->comm, inline_pc,
-			cpu, jiffies - started);
-	}
-}
-
-void _dbg_spin_unlock(spinlock_t * lock, const char *base_file, int line_no)
-{
-	CHECK_LOCK(lock);
-	volatile unsigned int *a;
-	mb();
-	a = __ldcw_align(lock);
-	if (unlikely((*a != 0) && lock->babble)) {
-		lock->babble--;
-		pdc_printf(
-			"%s:%d: spin_unlock(%s:%p) not locked\n",
-			base_file, line_no, lock->module, lock);
-	}
-	*a = 1;	
-	mb();
-}
-
-int _dbg_spin_trylock(spinlock_t * lock, const char *base_file, int line_no)
-{
-	int ret;
-	volatile unsigned int *a;
-	mb();
-	a = __ldcw_align(lock);
-	ret = (__ldcw(a) != 0);
-	mb();
-	if (ret) {
-		lock->oncpu = smp_processor_id();
-		lock->previous = __builtin_return_address(0);
-		lock->task = current;
-	} else {
-		lock->bfile = (char *)base_file;
-		lock->bline = line_no;
-	}
-	return ret;
-}
-
-#endif /* CONFIG_DEBUG_SPINLOCK */
-
-#ifdef CONFIG_DEBUG_RWLOCK
-
-/* Interrupts trouble detailed explanation, thx Grant:
- *
- * o writer (wants to modify data) attempts to acquire the rwlock
- * o He gets the write lock.
- * o Interupts are still enabled, we take an interrupt with the
- *   write still holding the lock.
- * o interrupt handler tries to acquire the rwlock for read.
- * o deadlock since the writer can't release it at this point.
- * 
- * In general, any use of spinlocks that competes between "base"
- * level and interrupt level code will risk deadlock. Interrupts
- * need to be disabled in the base level routines to avoid it.
- * Or more precisely, only the IRQ the base level routine
- * is competing with for the lock.  But it's more efficient/faster
- * to just disable all interrupts on that CPU to guarantee
- * once it gets the lock it can release it quickly too.
- */
- 
-void _dbg_write_lock(rwlock_t *rw, const char *bfile, int bline)
-{
-	void *inline_pc = __builtin_return_address(0);
-	unsigned long started = jiffies;
-	long stuck = INIT_STUCK;
-	int printed = 0;
-	int cpu = smp_processor_id();
-	
-	if(unlikely(in_interrupt())) {	/* acquiring write lock in interrupt context, bad idea */
-		pdc_printf("write_lock caller: %s:%d, IRQs enabled,\n", bfile, bline);
-		BUG();
-	}
-
-	/* Note: if interrupts are disabled (which is most likely), the printk
-	will never show on the console. We might need a polling method to flush
-	the dmesg buffer anyhow. */
-	
-retry:
-	_raw_spin_lock(&rw->lock);
-
-	if(rw->counter != 0) {
-		/* this basically never happens */
-		_raw_spin_unlock(&rw->lock);
-		
-		stuck--;
-		if ((unlikely(stuck <= 0)) && (rw->counter < 0)) {
-			pdc_printf(
-				"%s:%d: write_lock stuck on writer"
-				" in %s at %p(%d) %ld ticks\n",
-				bfile, bline, current->comm, inline_pc,
-				cpu, jiffies - started);
-			stuck = INIT_STUCK;
-			printed = 1;
-		}
-		else if (unlikely(stuck <= 0)) {
-			pdc_printf(
-				"%s:%d: write_lock stuck on reader"
-				" in %s at %p(%d) %ld ticks\n",
-				bfile, bline, current->comm, inline_pc,
-				cpu, jiffies - started);
-			stuck = INIT_STUCK;
-			printed = 1;
-		}
-		
-		while(rw->counter != 0);
-
-		goto retry;
-	}
-
-	/* got it.  now leave without unlocking */
-	rw->counter = -1; /* remember we are locked */
-
-	if (unlikely(printed)) {
-		pdc_printf(
-			"%s:%d: write_lock grabbed in %s at %p(%d) %ld ticks\n",
-			bfile, bline, current->comm, inline_pc,
-			cpu, jiffies - started);
-	}
-}
-
-int _dbg_write_trylock(rwlock_t *rw, const char *bfile, int bline)
-{
-#if 0
-	void *inline_pc = __builtin_return_address(0);
-	int cpu = smp_processor_id();
-#endif
-	
-	if(unlikely(in_interrupt())) {	/* acquiring write lock in interrupt context, bad idea */
-		pdc_printf("write_lock caller: %s:%d, IRQs enabled,\n", bfile, bline);
-		BUG();
-	}
-
-	/* Note: if interrupts are disabled (which is most likely), the printk
-	will never show on the console. We might need a polling method to flush
-	the dmesg buffer anyhow. */
-	
-	_raw_spin_lock(&rw->lock);
-
-	if(rw->counter != 0) {
-		/* this basically never happens */
-		_raw_spin_unlock(&rw->lock);
-		return 0;
-	}
-
-	/* got it.  now leave without unlocking */
-	rw->counter = -1; /* remember we are locked */
-#if 0
-	pdc_printf("%s:%d: try write_lock grabbed in %s at %p(%d)\n",
-		   bfile, bline, current->comm, inline_pc, cpu);
-#endif
-	return 1;
-}
-
-void _dbg_read_lock(rwlock_t * rw, const char *bfile, int bline)
-{
-#if 0
-	void *inline_pc = __builtin_return_address(0);
-	unsigned long started = jiffies;
-	int cpu = smp_processor_id();
-#endif
-	unsigned long flags;
-
-	local_irq_save(flags);
-	_raw_spin_lock(&rw->lock); 
-
-	rw->counter++;
-#if 0
-	pdc_printf(
-		"%s:%d: read_lock grabbed in %s at %p(%d) %ld ticks\n",
-		bfile, bline, current->comm, inline_pc,
-		cpu, jiffies - started);
-#endif
-	_raw_spin_unlock(&rw->lock);
-	local_irq_restore(flags);
-}
-
-#endif /* CONFIG_DEBUG_RWLOCK */