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Amerigo Wang 29671f22a8 rwsem: fix rwsem_is_locked() bugs 
rwsem_is_locked() tests ->activity without locks, so we should always keep
->activity consistent.  However, the code in __rwsem_do_wake() breaks this
rule, it updates ->activity after _all_ readers waken up, this may give
some reader a wrong ->activity value, thus cause rwsem_is_locked() behaves
wrong.

Quote from Andrew:

"
- we have one or more processes sleeping in down_read(), waiting for access.

- we wake one or more processes up without altering ->activity

- they start to run and they do rwsem_is_locked().  This incorrectly
  returns "false", because the waker process is still crunching away in
  __rwsem_do_wake().

- the waker now alters ->activity, but it was too late.
"

So we need get a spinlock to protect this.  And rwsem_is_locked() should
not block, thus we use spin_trylock_irqsave().

[akpm@linux-foundation.org: simplify code]
Reported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Cc: Ben Woodard <bwoodard@llnl.gov>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: WANG Cong <amwang@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2009-12-15 08:53:26 -08:00
..
lzo lzo: use get/put_unaligned_* helpers 2008-07-25 10:53:26 -07:00
reed_solomon lib: Remove unnecessary inclusions of asm/semaphore.h 2008-04-18 22:17:17 -04:00
zlib_deflate trivial: fix typo "to to" in multiple files 2009-09-21 15:14:55 +02:00
zlib_inflate bzip2/lzma: library support for gzip, bzip2 and lzma decompression 2009-01-04 15:53:34 -08:00
.gitignore Add some basic .gitignore files 2005-10-18 08:26:15 -07:00
Kconfig The DRBD driver 2009-10-01 21:17:49 +02:00
Kconfig.debug Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2009-12-10 09:35:44 -08:00
Kconfig.kgdb kgdb: remove the requirement for CONFIG_FRAME_POINTER 2008-08-01 08:39:34 -05:00
Kconfig.kmemcheck kmemcheck: depend on HAVE_ARCH_KMEMCHECK 2009-07-01 22:28:44 +02:00
Makefile The DRBD driver 2009-10-01 21:17:49 +02:00
argv_split.c LIB: Replace inappropriate include of <linux/bug.h> 2007-10-20 00:26:10 +02:00
atomic64.c lib: export generic atomic64_t functions 2009-07-29 19:10:35 -07:00
audit.c [PATCH] audit signal recipients 2007-05-11 05:38:25 -04:00
bcd.c rtc: BCD codeshrink 2008-07-24 10:47:33 -07:00
bitmap.c Make bitmask 'and' operators return a result code 2009-08-21 09:26:15 -07:00
bitrev.c lib: export bitrev16 2008-06-06 11:29:10 -07:00
bug.c allow bug table entries to use relative pointers (and use it on x86-64) 2008-12-16 18:40:32 +01:00
bust_spinlocks.c oops handling: ensure that any oops is flushed to the mtdoops console 2009-01-06 15:59:11 -08:00
check_signature.c uninline check_signature() 2007-07-16 09:05:50 -07:00
checksum.c lib/checksum: fix one more thinko 2009-11-03 16:06:53 +01:00
cmdline.c generic, memparse(): constify argument 2008-07-28 15:05:23 +02:00
cpumask.c x86: remove some alloc_bootmem_cpumask_var calling 2009-06-11 19:27:07 +03:00
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
crc-t10dif.c [SCSI] lib: Add support for the T10 (SCSI) Data Integrity Field CRC 2008-07-12 08:22:32 -05:00
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 Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
ctype.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
debug_locks.c lockdep: warn about lockdep disabling after kernel taint 2009-04-12 16:10:51 +02:00
debugobjects.c headers: remove sched.h from interrupt.h 2009-10-11 11:20:58 -07:00
dec_and_lock.c atomic: only take lock when the counter drops to zero on UP as well 2009-06-16 19:47:47 -07:00
decompress.c bzip2/lzma: don't stop search at first unconfigured compression 2009-02-19 13:36:55 -08:00
decompress_bunzip2.c tree-wide: fix assorted typos all over the place 2009-12-04 15:39:55 +01:00
decompress_inflate.c lzma/gzip: fix potential oops when input data is truncated 2009-09-24 07:21:05 -07:00
decompress_unlzma.c lzma/gzip: fix potential oops when input data is truncated 2009-09-24 07:21:05 -07:00
devres.c [POWERPC] devres: Add devm_ioremap_prot() 2008-05-05 16:47:14 +10:00
div64.c add an inlined version of iter_div_u64_rem 2008-06-12 10:47:58 +02:00
dma-debug.c tree-wide: fix assorted typos all over the place 2009-12-04 15:39:55 +01:00
dump_stack.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
dynamic_debug.c Dynamic debug: fix typo: -/-> 2009-07-28 13:45:22 -07:00
extable.c module: trim exception table on init free. 2009-06-12 21:47:04 +09:30
fault-inject.c headers: remove sched.h from interrupt.h 2009-10-11 11:20:58 -07:00
find_last_bit.c bitmap: find_last_bit() 2009-01-01 10:12:19 +10:30
find_next_bit.c bitops: remove "optimizations" 2008-04-29 08:11:16 -07:00
flex_array.c flex_array: add missing kerneldoc annotations 2009-09-22 07:17:47 -07:00
gcd.c lib: add lib/gcd.c 2009-06-18 13:04:05 -07:00
gen_crc32table.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
genalloc.c lib/genalloc.c: remove unmatched write_lock() in gen_pool_destroy 2009-06-16 19:47:53 -07:00
halfmd4.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
hexdump.c hexdump: remove the trailing space 2009-06-16 19:47:51 -07:00
hweight.c remove asm/bitops.h includes 2007-10-19 11:53:41 -07:00
idr.c tree-wide: fix some typos and punctuation in comments 2009-12-04 15:39:48 +01:00
inflate.c Nicolas Pitre has a new email address 2009-09-15 09:37:12 -07:00
int_sqrt.c [PATCH] lib: Fix bug in int_sqrt() for 64 bit longs 2006-02-03 08:32:08 -08:00
iomap.c Use WARN() in lib/ 2008-07-26 12:00:07 -07:00
iomap_copy.c [PATCH] add __iowrite64_copy 2006-06-20 20:24:58 -07:00
iommu-helper.c introduce generic iommu_num_pages function 2008-10-16 11:21:33 -07:00
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
is_single_threaded.c kernel: is_current_single_threaded: don't use ->mmap_sem 2009-07-17 09:11:31 +10:00
kasprintf.c lib: move kasprintf to a separate file 2007-07-31 15:39:39 -07:00
kernel_lock.c [BKL] add 'might_sleep()' to the outermost lock taker 2009-12-12 14:46:33 -08:00
klist.c driver core: Remove completion from struct klist_node 2009-01-06 10:44:30 -08:00
kobject.c kobject: make kset_create check kobject_set_name return value 2009-06-15 21:30:24 -07:00
kobject_uevent.c driver core: allow non-root users to listen to uevents 2009-04-16 16:17:09 -07:00
kref.c kref: add kref_set() 2008-01-24 20:40:05 -08:00
libcrc32c.c libcrc32c: Fix "crc32c undefined" compilation error 2008-12-25 11:01:42 +11:00
list_debug.c list debugging: use WARN() instead of BUG() 2008-07-25 10:53:29 -07:00
lmb.c lmb: Remove __init from lmb_end_of_DRAM() 2009-08-27 12:25:26 -07:00
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 locking: rename trace_softirq_[enter|exit] => lockdep_softirq_[enter|exit] 2009-03-13 01:32:36 +01:00
lru_cache.c The DRBD driver 2009-10-01 21:17:49 +02:00
nlattr.c Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/kaber/nf-next-2.6 2009-03-26 22:45:23 -07:00
parser.c vfs: Use const for kernel parser table 2008-10-13 10:10:37 -07:00
percpu_counter.c Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-01-06 17:10:04 -08:00
plist.c Use WARN() in lib/ 2008-07-26 12:00:07 -07:00
prio_heap.c lib: fix sparse shadowed variable warning 2009-01-06 15:59:11 -08:00
prio_tree.c Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
proportions.c Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-01-06 17:10:04 -08:00
radix-tree.c FS-Cache: Don't delete pending pages from the page-store tracking tree 2009-11-19 18:11:29 +00:00
random32.c random32: seeding improvement 2008-07-30 16:29:19 -07:00
ratelimit.c ratelimit: Make suppressed output messages more useful 2009-10-23 17:26:37 +02:00
rational.c lib: isolate rational fractions helper function 2009-06-11 08:51:08 -07:00
rbtree.c rb_tree: remove redundant if()-condition in rb_erase() 2009-06-16 19:47:56 -07:00
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 rwsem: fix rwsem_is_locked() bugs 2009-12-15 08:53:26 -08:00
rwsem.c x86: fix UML and -regparm=3 2008-01-30 13:33:00 +01:00
scatterlist.c lib/scatterlist: add a flags to signalize mapping direction 2009-07-31 12:28:45 +02:00
sha1.c [PATCH] Numerous fixes to kernel-doc info in source files. 2007-02-11 10:51:32 -08:00
show_mem.c lib: generic show_mem() 2008-07-26 12:00:10 -07:00
smp_processor_id.c cpumask: convert lib/smp_processor_id to new cpumask ops 2009-01-30 15:47:34 +01:00
sort.c generic swap(): lib/sort.c: rename swap to swap_func 2009-01-08 08:31:14 -08:00
spinlock_debug.c Use helpers to obtain task pid in printks 2007-10-19 11:53:43 -07:00
string.c strcmp: fix overflow and possibly signedness error 2009-11-18 17:18:13 -08:00
string_helpers.c [SCSI] lib: string_get_size(): don't hang on zero; no decimals on exact 2008-10-23 11:42:20 -05:00
swiotlb.c Merge branch 'for-next' into for-linus 2009-12-07 18:36:35 +01:00
syscall.c task_current_syscall 2008-07-26 12:00:10 -07:00
textsearch.c remove CONFIG_KMOD from lib 2008-07-22 19:24:31 +10:00
ts_bm.c textsearch: ts_bm: support case insensitive searching in Boyer-Moore algorithm 2008-07-08 02:37:54 -07:00
ts_fsm.c textsearch: ts_fsm: return error on request for case insensitive search 2008-07-08 02:38:27 -07:00
ts_kmp.c textsearch: ts_kmp: support case insensitive searching in Knuth-Morris-Pratt algorithm 2008-07-08 02:38:09 -07:00
vsprintf.c vsprintf: use %pR, %pr instead of %pRt, %pRf 2009-11-04 13:06:41 -08:00