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Linus Torvalds 8e3e076c5a BKL: revert back to the old spinlock implementation 
The generic semaphore rewrite had a huge performance regression on AIM7
(and potentially other BKL-heavy benchmarks) because the generic
semaphores had been rewritten to be simple to understand and fair.  The
latter, in particular, turns a semaphore-based BKL implementation into a
mess of scheduling.

The attempt to fix the performance regression failed miserably (see the
previous commit 00b41ec261 'Revert
"semaphore: fix"'), and so for now the simple and sane approach is to
instead just go back to the old spinlock-based BKL implementation that
never had any issues like this.

This patch also has the advantage of being reported to fix the
regression completely according to Yanmin Zhang, unlike the semaphore
hack which still left a couple percentage point regression.

As a spinlock, the BKL obviously has the potential to be a latency
issue, but it's not really any different from any other spinlock in that
respect.  We do want to get rid of the BKL asap, but that has been the
plan for several years.

These days, the biggest users are in the tty layer (open/release in
particular) and Alan holds out some hope:

  "tty release is probably a few months away from getting cured - I'm
   afraid it will almost certainly be the very last user of the BKL in
   tty to get fixed as it depends on everything else being sanely locked."

so while we're not there yet, we do have a plan of action.

Tested-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: Alexander Viro <viro@ftp.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-05-10 20:58:02 -07:00
..
lzo lzo: fix typo in decompressor 2008-04-10 15:34:05 -07:00
reed_solomon lib: Remove unnecessary inclusions of asm/semaphore.h 2008-04-18 22:17:17 -04:00
zlib_deflate lib/: Spelling fixes 2008-02-03 17:48:52 +02:00
zlib_inflate [ZLIB]: Fix external builds of zlib_inflate code. 2007-10-11 22:17:20 -07:00
.gitignore
argv_split.c LIB: Replace inappropriate include of <linux/bug.h> 2007-10-20 00:26:10 +02:00
audit.c [PATCH] audit signal recipients 2007-05-11 05:38:25 -04:00
bitmap.c mempolicy: add bitmap_onto() and bitmap_fold() operations 2008-04-28 08:58:19 -07:00
bitrev.c [PATCH] add MODULE_* attributes to bit reversal library 2006-12-10 10:07:52 -08:00
bug.c generic bug: use show_regs() instead of dump_stack() 2007-07-16 09:05:51 -07:00
bust_spinlocks.c handle recursive calls to bust_spinlocks() 2007-10-17 08:42:56 -07:00
check_signature.c uninline check_signature() 2007-07-16 09:05:50 -07:00
cmdline.c [PATCH] Numerous fixes to kernel-doc info in source files. 2007-02-11 10:51:32 -08:00
cpumask.c Safer nr_node_ids and nr_node_ids determination and initial values 2007-05-07 12:12:51 -07:00
crc7.c CRC7 support 2007-07-17 10:23:04 -07:00
crc16.c [PATCH] kernel-doc for lib/crc*.c 2006-06-25 10:01:20 -07:00
crc32.c lib/: Spelling fixes 2008-02-03 17:48:52 +02:00
crc32defs.h
crc-ccitt.c [PATCH] kernel-doc for lib/crc*.c 2006-06-25 10:01:20 -07:00
crc-itu-t.c CRC ITU-T V.41 2007-05-10 18:24:13 +02:00
ctype.c
debug_locks.c [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
debugobjects.c infrastructure to debug (dynamic) objects 2008-04-30 08:29:53 -07:00
dec_and_lock.c
devres.c [POWERPC] devres: Add devm_ioremap_prot() 2008-05-05 16:47:14 +10:00
div64.c rename div64_64 to div64_u64 2008-05-01 08:03:58 -07:00
dump_stack.c
extable.c lib/extable.c: remove an expensive integer divide in search_extable() 2008-02-06 10:41:08 -08:00
fault-inject.c libfs: allow error return from simple attributes 2008-02-08 09:22:34 -08:00
find_next_bit.c bitops: remove "optimizations" 2008-04-29 08:11:16 -07:00
gen_crc32table.c
genalloc.c Slab allocators: Replace explicit zeroing with __GFP_ZERO 2007-07-17 10:23:02 -07:00
halfmd4.c
hexdump.c hexdump: don't print bytes with bit 7 set 2007-11-29 09:24:53 -08:00
hweight.c remove asm/bitops.h includes 2007-10-19 11:53:41 -07:00
idr.c idr: fix idr_remove() 2008-05-01 08:04:00 -07:00
inflate.c lib/inflate.c: handle failed malloc() 2008-04-29 08:06:02 -07:00
int_sqrt.c
iomap_copy.c [PATCH] add __iowrite64_copy 2006-06-20 20:24:58 -07:00
iomap.c iomap: fix 64 bits resources on 32 bits 2008-04-29 08:06:02 -07:00
iommu-helper.c iommu: export iommu_is_span_boundary helper function 2008-03-04 16:35:17 -08:00
ioremap.c lib/ioremap.c should #include <linux/io.h> 2007-10-17 08:42:50 -07:00
irq_regs.c [PATCH] irq_reqs: export __irq_regs 2006-10-06 08:53:40 -07:00
kasprintf.c lib: move kasprintf to a separate file 2007-07-31 15:39:39 -07:00
Kconfig x86, bitops: select the generic bitmap search functions 2008-04-26 19:21:17 +02:00
Kconfig.debug debugobjects: add timer specific object debugging code 2008-04-30 08:29:53 -07:00
Kconfig.kgdb kgdb: kconfig fix xconfig/menuconfig element 2008-05-05 07:13:21 -05:00
kernel_lock.c BKL: revert back to the old spinlock implementation 2008-05-10 20:58:02 -07:00
klist.c klist: fix coding style errors in klist.h and klist.c 2008-04-30 16:52:58 -07:00
kobject_uevent.c lib: replace remaining __FUNCTION__ occurrences 2008-04-30 08:29:54 -07:00
kobject.c kobject: do not copy vargs, just pass them around 2008-04-30 16:52:48 -07:00
kref.c kref: add kref_set() 2008-01-24 20:40:05 -08:00
libcrc32c.c [LIB] crc32c: Keep intermediate crc state in cpu order 2007-11-08 21:34:09 +08:00
list_debug.c [PATCH] More list debugging context 2006-12-07 08:39:35 -08:00
lmb.c [POWERPC] Provide walk_memory_resource() for powerpc 2008-04-29 15:57:53 +10:00
locking-selftest-hardirq.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-mutex.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-rlock-hardirq.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-rlock-softirq.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-rlock.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-rsem.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-softirq.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-spin-hardirq.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-spin-softirq.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-spin.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-wlock-hardirq.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-wlock-softirq.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-wlock.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest-wsem.h [PATCH] lockdep: locking API self tests 2006-07-03 15:27:03 -07:00
locking-selftest.c [PATCH] lockdep: show more details about self-test failures 2006-12-07 08:39:43 -08:00
Makefile infrastructure to debug (dynamic) objects 2008-04-30 08:29:53 -07:00
parser.c [AFS]: Make the match_*() functions take const options. 2007-05-03 03:10:39 -07:00
percpu_counter.c mm: bdi: export BDI attributes in sysfs 2008-04-30 08:29:49 -07:00
plist.c [PATCH] pi-futex: add plist implementation 2006-06-27 17:32:46 -07:00
prio_heap.c Fix cpusets update_cpumask 2007-10-19 11:53:41 -07:00
prio_tree.c
proportions.c mm: bdi: allow setting a maximum for the bdi dirty limit 2008-04-30 08:29:50 -07:00
radix-tree.c Remove set_migrateflags() 2008-04-28 08:58:17 -07:00
random32.c [NET]: srandom32 fixes for networking v2 2008-04-03 14:07:02 -07:00
ratelimit.c isolate ratelimit from printk.c for other use 2008-04-29 08:06:06 -07:00
rbtree.c [PATCH] rbtree: fixed reversed RB_EMPTY_NODE and rb_next/prev 2006-09-30 20:26:56 +02:00
reciprocal_div.c [PATCH] SLAB: use a multiply instead of a divide in obj_to_index() 2006-12-13 09:05:49 -08:00
rwsem-spinlock.c lib: remove fastcall from lib/* 2008-02-08 09:22:31 -08:00
rwsem.c x86: fix UML and -regparm=3 2008-01-30 13:33:00 +01:00
scatterlist.c [SCSI] block: add sg buffer copy helper functions 2008-04-07 12:15:45 -05:00
sha1.c [PATCH] Numerous fixes to kernel-doc info in source files. 2007-02-11 10:51:32 -08:00
smp_processor_id.c debug_smp_processor_id() fixlets 2008-02-06 10:41:09 -08:00
sort.c lib/sort.c optimization 2007-10-17 08:42:52 -07:00
spinlock_debug.c Use helpers to obtain task pid in printks 2007-10-19 11:53:43 -07:00
string.c Add a new sysfs_streq() string comparison function 2008-05-01 08:03:59 -07:00
swiotlb.c dma/ia64: update ia64 machvecs, swiotlb.c 2008-04-29 08:06:12 -07:00
textsearch.c [TEXTSEARCH]: Do not allow zero length patterns in the textsearch infrastructure 2007-12-01 00:03:52 +11:00
ts_bm.c [TEXTSEARCH]: Fix Boyer Moore initialization bug 2006-08-22 14:33:58 -07:00
ts_fsm.c [PATCH] lib/ts_fsm.c: constify structs 2006-09-29 09:18:23 -07:00
ts_kmp.c Remove obsolete #include <linux/config.h> 2006-06-30 19:25:36 +02:00
vsprintf.c lib/vsprintf.c: fix bug omitting minus sign of numbers (module_param) 2008-02-23 17:12:14 -08:00