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[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>
This commit is contained in:
Ingo Molnar
committed by
Linus Torvalds
Linus Torvalds
parent
4327edf6b8
commit
fb1c8f93d8
@@ -5,5 +5,3 @@
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lib-y := lusercopy.o bitops.o checksum.o io.o memset.o fixup.o memcpy.o
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obj-y := iomap.o
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lib-$(CONFIG_SMP) += debuglocks.o
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@@ -13,8 +13,8 @@
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#include <asm/atomic.h>
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#ifdef CONFIG_SMP
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spinlock_t __atomic_hash[ATOMIC_HASH_SIZE] __lock_aligned = {
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[0 ... (ATOMIC_HASH_SIZE-1)] = SPIN_LOCK_UNLOCKED
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raw_spinlock_t __atomic_hash[ATOMIC_HASH_SIZE] __lock_aligned = {
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[0 ... (ATOMIC_HASH_SIZE-1)] = __RAW_SPIN_LOCK_UNLOCKED
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};
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#endif
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@@ -1,277 +0,0 @@
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/*
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* Debugging versions of SMP locking primitives.
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*
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* Copyright (C) 2004 Thibaut VARENE <varenet@parisc-linux.org>
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*
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* Some code stollen from alpha & sparc64 ;)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* We use pdc_printf() throughout the file for all output messages, to avoid
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* losing messages because of disabled interrupts. Since we're using these
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* messages for debugging purposes, it makes sense not to send them to the
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* linux console.
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*/
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#include <linux/config.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/spinlock.h>
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#include <linux/hardirq.h> /* in_interrupt() */
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#include <asm/system.h>
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#include <asm/hardirq.h> /* in_interrupt() */
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#include <asm/pdc.h>
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#undef INIT_STUCK
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#define INIT_STUCK 1L << 30
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#ifdef CONFIG_DEBUG_SPINLOCK
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void _dbg_spin_lock(spinlock_t * lock, const char *base_file, int line_no)
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{
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volatile unsigned int *a;
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long stuck = INIT_STUCK;
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void *inline_pc = __builtin_return_address(0);
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unsigned long started = jiffies;
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int printed = 0;
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int cpu = smp_processor_id();
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try_again:
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/* Do the actual locking */
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/* <T-Bone> ggg: we can't get stuck on the outter loop?
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* <ggg> T-Bone: We can hit the outer loop
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* alot if multiple CPUs are constantly racing for a lock
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* and the backplane is NOT fair about which CPU sees
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* the update first. But it won't hang since every failed
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* attempt will drop us back into the inner loop and
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* decrement `stuck'.
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* <ggg> K-class and some of the others are NOT fair in the HW
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* implementation so we could see false positives.
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* But fixing the lock contention is easier than
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* fixing the HW to be fair.
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* <tausq> __ldcw() returns 1 if we get the lock; otherwise we
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* spin until the value of the lock changes, or we time out.
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*/
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mb();
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a = __ldcw_align(lock);
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while (stuck && (__ldcw(a) == 0))
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while ((*a == 0) && --stuck);
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mb();
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if (unlikely(stuck <= 0)) {
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pdc_printf(
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"%s:%d: spin_lock(%s/%p) stuck in %s at %p(%d)"
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" owned by %s:%d in %s at %p(%d)\n",
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base_file, line_no, lock->module, lock,
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current->comm, inline_pc, cpu,
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lock->bfile, lock->bline, lock->task->comm,
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lock->previous, lock->oncpu);
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stuck = INIT_STUCK;
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printed = 1;
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goto try_again;
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}
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/* Exiting. Got the lock. */
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lock->oncpu = cpu;
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lock->previous = inline_pc;
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lock->task = current;
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lock->bfile = (char *)base_file;
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lock->bline = line_no;
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if (unlikely(printed)) {
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pdc_printf(
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"%s:%d: spin_lock grabbed in %s at %p(%d) %ld ticks\n",
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base_file, line_no, current->comm, inline_pc,
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cpu, jiffies - started);
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}
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}
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void _dbg_spin_unlock(spinlock_t * lock, const char *base_file, int line_no)
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{
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CHECK_LOCK(lock);
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volatile unsigned int *a;
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mb();
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a = __ldcw_align(lock);
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if (unlikely((*a != 0) && lock->babble)) {
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lock->babble--;
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pdc_printf(
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"%s:%d: spin_unlock(%s:%p) not locked\n",
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base_file, line_no, lock->module, lock);
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}
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*a = 1;
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mb();
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}
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int _dbg_spin_trylock(spinlock_t * lock, const char *base_file, int line_no)
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{
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int ret;
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volatile unsigned int *a;
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mb();
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a = __ldcw_align(lock);
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ret = (__ldcw(a) != 0);
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mb();
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if (ret) {
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lock->oncpu = smp_processor_id();
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lock->previous = __builtin_return_address(0);
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lock->task = current;
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} else {
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lock->bfile = (char *)base_file;
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lock->bline = line_no;
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}
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return ret;
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}
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#endif /* CONFIG_DEBUG_SPINLOCK */
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#ifdef CONFIG_DEBUG_RWLOCK
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/* Interrupts trouble detailed explanation, thx Grant:
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*
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* o writer (wants to modify data) attempts to acquire the rwlock
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* o He gets the write lock.
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* o Interupts are still enabled, we take an interrupt with the
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* write still holding the lock.
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* o interrupt handler tries to acquire the rwlock for read.
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* o deadlock since the writer can't release it at this point.
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*
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* In general, any use of spinlocks that competes between "base"
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* level and interrupt level code will risk deadlock. Interrupts
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* need to be disabled in the base level routines to avoid it.
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* Or more precisely, only the IRQ the base level routine
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* is competing with for the lock. But it's more efficient/faster
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* to just disable all interrupts on that CPU to guarantee
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* once it gets the lock it can release it quickly too.
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*/
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void _dbg_write_lock(rwlock_t *rw, const char *bfile, int bline)
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{
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void *inline_pc = __builtin_return_address(0);
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unsigned long started = jiffies;
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long stuck = INIT_STUCK;
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int printed = 0;
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int cpu = smp_processor_id();
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if(unlikely(in_interrupt())) { /* acquiring write lock in interrupt context, bad idea */
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pdc_printf("write_lock caller: %s:%d, IRQs enabled,\n", bfile, bline);
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BUG();
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}
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/* Note: if interrupts are disabled (which is most likely), the printk
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will never show on the console. We might need a polling method to flush
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the dmesg buffer anyhow. */
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retry:
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_raw_spin_lock(&rw->lock);
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if(rw->counter != 0) {
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/* this basically never happens */
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_raw_spin_unlock(&rw->lock);
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stuck--;
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if ((unlikely(stuck <= 0)) && (rw->counter < 0)) {
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pdc_printf(
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"%s:%d: write_lock stuck on writer"
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" in %s at %p(%d) %ld ticks\n",
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bfile, bline, current->comm, inline_pc,
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cpu, jiffies - started);
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stuck = INIT_STUCK;
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printed = 1;
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}
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else if (unlikely(stuck <= 0)) {
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pdc_printf(
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"%s:%d: write_lock stuck on reader"
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" in %s at %p(%d) %ld ticks\n",
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bfile, bline, current->comm, inline_pc,
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cpu, jiffies - started);
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stuck = INIT_STUCK;
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printed = 1;
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}
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while(rw->counter != 0);
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goto retry;
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}
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/* got it. now leave without unlocking */
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rw->counter = -1; /* remember we are locked */
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if (unlikely(printed)) {
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pdc_printf(
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"%s:%d: write_lock grabbed in %s at %p(%d) %ld ticks\n",
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bfile, bline, current->comm, inline_pc,
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cpu, jiffies - started);
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}
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}
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int _dbg_write_trylock(rwlock_t *rw, const char *bfile, int bline)
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{
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#if 0
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void *inline_pc = __builtin_return_address(0);
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int cpu = smp_processor_id();
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#endif
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if(unlikely(in_interrupt())) { /* acquiring write lock in interrupt context, bad idea */
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pdc_printf("write_lock caller: %s:%d, IRQs enabled,\n", bfile, bline);
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BUG();
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}
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/* Note: if interrupts are disabled (which is most likely), the printk
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will never show on the console. We might need a polling method to flush
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the dmesg buffer anyhow. */
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_raw_spin_lock(&rw->lock);
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if(rw->counter != 0) {
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/* this basically never happens */
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_raw_spin_unlock(&rw->lock);
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return 0;
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}
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/* got it. now leave without unlocking */
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rw->counter = -1; /* remember we are locked */
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#if 0
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pdc_printf("%s:%d: try write_lock grabbed in %s at %p(%d)\n",
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bfile, bline, current->comm, inline_pc, cpu);
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#endif
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return 1;
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}
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void _dbg_read_lock(rwlock_t * rw, const char *bfile, int bline)
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{
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#if 0
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void *inline_pc = __builtin_return_address(0);
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unsigned long started = jiffies;
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int cpu = smp_processor_id();
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#endif
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unsigned long flags;
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local_irq_save(flags);
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_raw_spin_lock(&rw->lock);
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rw->counter++;
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#if 0
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pdc_printf(
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"%s:%d: read_lock grabbed in %s at %p(%d) %ld ticks\n",
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bfile, bline, current->comm, inline_pc,
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cpu, jiffies - started);
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#endif
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_raw_spin_unlock(&rw->lock);
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local_irq_restore(flags);
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}
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#endif /* CONFIG_DEBUG_RWLOCK */
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