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authorIngo Molnar <mingo@elte.hu>2005-09-10 00:25:56 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2005-09-10 10:06:21 -0700
commitfb1c8f93d869b34cacb8b8932e2b83d96a19d720 (patch)
treea006d078aa02e421a7dc4793c335308204859d36 /lib
parent4327edf6b8a7ac7dce144313947995538842d8fd (diff)
[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>
Diffstat (limited to 'lib')
-rw-r--r--lib/Makefile1
-rw-r--r--lib/dec_and_lock.c3
-rw-r--r--lib/kernel_lock.c3
-rw-r--r--lib/spinlock_debug.c257
4 files changed, 259 insertions, 5 deletions
diff --git a/lib/Makefile b/lib/Makefile
index d9c38ba05e7b..44a46750690a 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -16,6 +16,7 @@ CFLAGS_kobject.o += -DDEBUG
CFLAGS_kobject_uevent.o += -DDEBUG
endif
+obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock_debug.o
lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
lib-$(CONFIG_SEMAPHORE_SLEEPERS) += semaphore-sleepers.o
diff --git a/lib/dec_and_lock.c b/lib/dec_and_lock.c
index 6658d81e1836..2377af057d09 100644
--- a/lib/dec_and_lock.c
+++ b/lib/dec_and_lock.c
@@ -25,8 +25,6 @@
* this is trivially done efficiently using a load-locked
* store-conditional approach, for example.
*/
-
-#ifndef ATOMIC_DEC_AND_LOCK
int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
{
spin_lock(lock);
@@ -37,4 +35,3 @@ int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock)
}
EXPORT_SYMBOL(_atomic_dec_and_lock);
-#endif
diff --git a/lib/kernel_lock.c b/lib/kernel_lock.c
index bd2bc5d887b8..cb5490ec00f2 100644
--- a/lib/kernel_lock.c
+++ b/lib/kernel_lock.c
@@ -177,8 +177,7 @@ static inline void __lock_kernel(void)
static inline void __unlock_kernel(void)
{
- _raw_spin_unlock(&kernel_flag);
- preempt_enable();
+ spin_unlock(&kernel_flag);
}
/*
diff --git a/lib/spinlock_debug.c b/lib/spinlock_debug.c
new file mode 100644
index 000000000000..906ad101eab3
--- /dev/null
+++ b/lib/spinlock_debug.c
@@ -0,0 +1,257 @@
+/*
+ * Copyright 2005, Red Hat, Inc., Ingo Molnar
+ * Released under the General Public License (GPL).
+ *
+ * This file contains the spinlock/rwlock implementations for
+ * DEBUG_SPINLOCK.
+ */
+
+#include <linux/config.h>
+#include <linux/spinlock.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+
+static void spin_bug(spinlock_t *lock, const char *msg)
+{
+ static long print_once = 1;
+ struct task_struct *owner = NULL;
+
+ if (xchg(&print_once, 0)) {
+ if (lock->owner && lock->owner != SPINLOCK_OWNER_INIT)
+ owner = lock->owner;
+ printk("BUG: spinlock %s on CPU#%d, %s/%d\n",
+ msg, smp_processor_id(), current->comm, current->pid);
+ printk(" lock: %p, .magic: %08x, .owner: %s/%d, .owner_cpu: %d\n",
+ lock, lock->magic,
+ owner ? owner->comm : "<none>",
+ owner ? owner->pid : -1,
+ lock->owner_cpu);
+ dump_stack();
+#ifdef CONFIG_SMP
+ /*
+ * We cannot continue on SMP:
+ */
+// panic("bad locking");
+#endif
+ }
+}
+
+#define SPIN_BUG_ON(cond, lock, msg) if (unlikely(cond)) spin_bug(lock, msg)
+
+static inline void debug_spin_lock_before(spinlock_t *lock)
+{
+ SPIN_BUG_ON(lock->magic != SPINLOCK_MAGIC, lock, "bad magic");
+ SPIN_BUG_ON(lock->owner == current, lock, "recursion");
+ SPIN_BUG_ON(lock->owner_cpu == raw_smp_processor_id(),
+ lock, "cpu recursion");
+}
+
+static inline void debug_spin_lock_after(spinlock_t *lock)
+{
+ lock->owner_cpu = raw_smp_processor_id();
+ lock->owner = current;
+}
+
+static inline void debug_spin_unlock(spinlock_t *lock)
+{
+ SPIN_BUG_ON(lock->magic != SPINLOCK_MAGIC, lock, "bad magic");
+ SPIN_BUG_ON(!spin_is_locked(lock), lock, "already unlocked");
+ SPIN_BUG_ON(lock->owner != current, lock, "wrong owner");
+ SPIN_BUG_ON(lock->owner_cpu != raw_smp_processor_id(),
+ lock, "wrong CPU");
+ lock->owner = SPINLOCK_OWNER_INIT;
+ lock->owner_cpu = -1;
+}
+
+static void __spin_lock_debug(spinlock_t *lock)
+{
+ int print_once = 1;
+ u64 i;
+
+ for (;;) {
+ for (i = 0; i < loops_per_jiffy * HZ; i++) {
+ cpu_relax();
+ if (__raw_spin_trylock(&lock->raw_lock))
+ return;
+ }
+ /* lockup suspected: */
+ if (print_once) {
+ print_once = 0;
+ printk("BUG: spinlock lockup on CPU#%d, %s/%d, %p\n",
+ smp_processor_id(), current->comm, current->pid,
+ lock);
+ dump_stack();
+ }
+ }
+}
+
+void _raw_spin_lock(spinlock_t *lock)
+{
+ debug_spin_lock_before(lock);
+ if (unlikely(!__raw_spin_trylock(&lock->raw_lock)))
+ __spin_lock_debug(lock);
+ debug_spin_lock_after(lock);
+}
+
+int _raw_spin_trylock(spinlock_t *lock)
+{
+ int ret = __raw_spin_trylock(&lock->raw_lock);
+
+ if (ret)
+ debug_spin_lock_after(lock);
+#ifndef CONFIG_SMP
+ /*
+ * Must not happen on UP:
+ */
+ SPIN_BUG_ON(!ret, lock, "trylock failure on UP");
+#endif
+ return ret;
+}
+
+void _raw_spin_unlock(spinlock_t *lock)
+{
+ debug_spin_unlock(lock);
+ __raw_spin_unlock(&lock->raw_lock);
+}
+
+static void rwlock_bug(rwlock_t *lock, const char *msg)
+{
+ static long print_once = 1;
+
+ if (xchg(&print_once, 0)) {
+ printk("BUG: rwlock %s on CPU#%d, %s/%d, %p\n", msg,
+ smp_processor_id(), current->comm, current->pid, lock);
+ dump_stack();
+#ifdef CONFIG_SMP
+ /*
+ * We cannot continue on SMP:
+ */
+ panic("bad locking");
+#endif
+ }
+}
+
+#define RWLOCK_BUG_ON(cond, lock, msg) if (unlikely(cond)) rwlock_bug(lock, msg)
+
+static void __read_lock_debug(rwlock_t *lock)
+{
+ int print_once = 1;
+ u64 i;
+
+ for (;;) {
+ for (i = 0; i < loops_per_jiffy * HZ; i++) {
+ cpu_relax();
+ if (__raw_read_trylock(&lock->raw_lock))
+ return;
+ }
+ /* lockup suspected: */
+ if (print_once) {
+ print_once = 0;
+ printk("BUG: read-lock lockup on CPU#%d, %s/%d, %p\n",
+ smp_processor_id(), current->comm, current->pid,
+ lock);
+ dump_stack();
+ }
+ }
+}
+
+void _raw_read_lock(rwlock_t *lock)
+{
+ RWLOCK_BUG_ON(lock->magic != RWLOCK_MAGIC, lock, "bad magic");
+ if (unlikely(!__raw_read_trylock(&lock->raw_lock)))
+ __read_lock_debug(lock);
+}
+
+int _raw_read_trylock(rwlock_t *lock)
+{
+ int ret = __raw_read_trylock(&lock->raw_lock);
+
+#ifndef CONFIG_SMP
+ /*
+ * Must not happen on UP:
+ */
+ RWLOCK_BUG_ON(!ret, lock, "trylock failure on UP");
+#endif
+ return ret;
+}
+
+void _raw_read_unlock(rwlock_t *lock)
+{
+ RWLOCK_BUG_ON(lock->magic != RWLOCK_MAGIC, lock, "bad magic");
+ __raw_read_unlock(&lock->raw_lock);
+}
+
+static inline void debug_write_lock_before(rwlock_t *lock)
+{
+ RWLOCK_BUG_ON(lock->magic != RWLOCK_MAGIC, lock, "bad magic");
+ RWLOCK_BUG_ON(lock->owner == current, lock, "recursion");
+ RWLOCK_BUG_ON(lock->owner_cpu == raw_smp_processor_id(),
+ lock, "cpu recursion");
+}
+
+static inline void debug_write_lock_after(rwlock_t *lock)
+{
+ lock->owner_cpu = raw_smp_processor_id();
+ lock->owner = current;
+}
+
+static inline void debug_write_unlock(rwlock_t *lock)
+{
+ RWLOCK_BUG_ON(lock->magic != RWLOCK_MAGIC, lock, "bad magic");
+ RWLOCK_BUG_ON(lock->owner != current, lock, "wrong owner");
+ RWLOCK_BUG_ON(lock->owner_cpu != raw_smp_processor_id(),
+ lock, "wrong CPU");
+ lock->owner = SPINLOCK_OWNER_INIT;
+ lock->owner_cpu = -1;
+}
+
+static void __write_lock_debug(rwlock_t *lock)
+{
+ int print_once = 1;
+ u64 i;
+
+ for (;;) {
+ for (i = 0; i < loops_per_jiffy * HZ; i++) {
+ cpu_relax();
+ if (__raw_write_trylock(&lock->raw_lock))
+ return;
+ }
+ /* lockup suspected: */
+ if (print_once) {
+ print_once = 0;
+ printk("BUG: write-lock lockup on CPU#%d, %s/%d, %p\n",
+ smp_processor_id(), current->comm, current->pid,
+ lock);
+ dump_stack();
+ }
+ }
+}
+
+void _raw_write_lock(rwlock_t *lock)
+{
+ debug_write_lock_before(lock);
+ if (unlikely(!__raw_write_trylock(&lock->raw_lock)))
+ __write_lock_debug(lock);
+ debug_write_lock_after(lock);
+}
+
+int _raw_write_trylock(rwlock_t *lock)
+{
+ int ret = __raw_write_trylock(&lock->raw_lock);
+
+ if (ret)
+ debug_write_lock_after(lock);
+#ifndef CONFIG_SMP
+ /*
+ * Must not happen on UP:
+ */
+ RWLOCK_BUG_ON(!ret, lock, "trylock failure on UP");
+#endif
+ return ret;
+}
+
+void _raw_write_unlock(rwlock_t *lock)
+{
+ debug_write_unlock(lock);
+ __raw_write_unlock(&lock->raw_lock);
+}

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