[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>
diff --git a/arch/parisc/lib/Makefile b/arch/parisc/lib/Makefile
index 7bf7056..5f2e690 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 2de182f..90f400b 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 1b33fe6..0000000
--- 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 */