[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/lib/spinlock_debug.c b/lib/spinlock_debug.c
new file mode 100644
index 0000000..906ad10
--- /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);
+}