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Petr Mladek 42a0bb3f71 printk/nmi: generic solution for safe printk in NMI 
printk() takes some locks and could not be used a safe way in NMI
context.

The chance of a deadlock is real especially when printing stacks from
all CPUs.  This particular problem has been addressed on x86 by the
commit a9edc88093 ("x86/nmi: Perform a safe NMI stack trace on all
CPUs").

The patchset brings two big advantages.  First, it makes the NMI
backtraces safe on all architectures for free.  Second, it makes all NMI
messages almost safe on all architectures (the temporary buffer is
limited.  We still should keep the number of messages in NMI context at
minimum).

Note that there already are several messages printed in NMI context:
WARN_ON(in_nmi()), BUG_ON(in_nmi()), anything being printed out from MCE
handlers.  These are not easy to avoid.

This patch reuses most of the code and makes it generic.  It is useful
for all messages and architectures that support NMI.

The alternative printk_func is set when entering and is reseted when
leaving NMI context.  It queues IRQ work to copy the messages into the
main ring buffer in a safe context.

__printk_nmi_flush() copies all available messages and reset the buffer.
Then we could use a simple cmpxchg operations to get synchronized with
writers.  There is also used a spinlock to get synchronized with other
flushers.

We do not longer use seq_buf because it depends on external lock.  It
would be hard to make all supported operations safe for a lockless use.
It would be confusing and error prone to make only some operations safe.

The code is put into separate printk/nmi.c as suggested by Steven
Rostedt.  It needs a per-CPU buffer and is compiled only on
architectures that call nmi_enter().  This is achieved by the new
HAVE_NMI Kconfig flag.

The are MN10300 and Xtensa architectures.  We need to clean up NMI
handling there first.  Let's do it separately.

The patch is heavily based on the draft from Peter Zijlstra, see

  https://lkml.org/lkml/2015/6/10/327

[arnd@arndb.de: printk-nmi: use %zu format string for size_t]
[akpm@linux-foundation.org: min_t->min - all types are size_t here]
Signed-off-by: Petr Mladek <pmladek@suse.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Jan Kara <jack@suse.cz>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>	[arm part]
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jiri Kosina <jkosina@suse.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: David Miller <davem@davemloft.net>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2016-05-20 17:58:30 -07:00
..
842 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2016-03-17 21:38:27 -07:00
fonts fonts: Add 6x10 font 2014-10-09 11:35:48 +03:00
lz4 lib: lz4: cleanup unaligned access efficiency detection 2016-04-13 09:22:49 -07:00
lzo lzo: check for length overrun in variable length encoding. 2014-09-28 11:08:01 +02:00
mpi lib/mpi: mpi_read_raw_from_sgl(): fix out-of-bounds buffer access 2016-04-05 20:35:51 +08:00
raid6 powerpc: Create disable_kernel_{fp,altivec,vsx,spe}() 2015-12-01 13:52:25 +11:00
reed_solomon
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xz lib/xz: enable all filters by default in Kconfig 2014-06-04 16:54:18 -07:00
zlib_deflate zlib_deflate/deftree: remove bi_reverse() 2015-09-10 13:29:01 -07:00
zlib_inflate zlib: clean up some dead code 2014-08-06 18:01:24 -07:00
.gitignore
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Kconfig lib: scatterlist: move SG pool code from SCSI driver to lib/sg_pool.c 2016-04-15 16:53:14 -04:00
Kconfig.debug rcutorture: Add RCU grace-period performance tests 2016-03-31 13:37:38 -07:00
Kconfig.kasan mm, kasan: stackdepot implementation. Enable stackdepot for SLAB 2016-03-25 16:37:42 -07:00
Kconfig.kgdb kdb: Allow access to sensitive commands to be restricted by default 2014-11-11 09:31:52 -06:00
Kconfig.kmemcheck
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Kconfig.ubsan ubsan: fix tree-wide -Wmaybe-uninitialized false positives 2016-03-22 15:36:02 -07:00
Makefile include/linux/nodemask.h: create next_node_in() helper 2016-05-19 19:12:14 -07:00
argv_split.c
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asn1_decoder.c Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2016-05-17 09:33:39 -07:00
assoc_array.c assoc_array: don't call compare_object() on a node 2016-04-06 14:06:48 +01:00
atomic64.c atomic: Provide atomic_{or,xor,and} 2015-07-27 14:06:24 +02:00
atomic64_test.c x86/cpufeature: Carve out X86_FEATURE_* 2016-01-30 11:22:17 +01:00
audit.c syscalls: implement execveat() system call 2014-12-13 12:42:51 -08:00
bcd.c
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bch.c
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bitmap.c lib/bitmap.c: conversion routines to/from u32 array 2016-02-19 22:54:09 -05:00
bitrev.c ARM: 8187/1: add CONFIG_HAVE_ARCH_BITREVERSE to support rbit instruction 2014-12-22 16:43:06 +00:00
bsearch.c
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btree.c treewide: Remove old email address 2015-11-23 09:44:58 +01:00
bug.c lib/bug.c: use common WARN helper 2016-03-17 15:09:34 -07:00
build_OID_registry
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bust_spinlocks.c
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check_signature.c
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checksum.c ipv4: Update parameters for csum_tcpudp_magic to their original types 2016-03-13 23:55:13 -04:00
clz_ctz.c lib/clz_ctz.c: add prototype declarations in lib/clz_ctz.c 2014-04-03 16:21:12 -07:00
clz_tab.c
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cmdline.c lib: Add a generic cmdline parse function parse_option_str 2014-10-03 18:40:58 +01:00
compat_audit.c
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cordic.c
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cpu-notifier-error-inject.c
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cpu_rmap.c sched/topology: Rename topology_thread_cpumask() to topology_sibling_cpumask() 2015-05-27 15:22:15 +02:00
cpumask.c cpumask: Export cpumask_any_but() 2016-02-29 09:35:20 +01:00
crc-ccitt.c
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crc-itu-t.c lib: crc-itu-t.[ch] fix 0x0x prefix in integer constants 2015-05-26 15:26:43 +02:00
crc-t10dif.c lib: introduce crc_t10dif_update() 2015-05-30 22:42:24 -07:00
crc7.c lib/crc7: Shift crc7() output left 1 bit 2014-05-16 14:26:52 -04:00
crc8.c
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crc16.c
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crc32.c lib: crc32: Add some additional __pure annotations 2014-06-25 16:04:00 -07:00
crc32defs.h
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ctype.c
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debug_info.c kbuild: include core debug info when DEBUG_INFO_REDUCED 2015-06-11 15:08:32 +02:00
debug_locks.c
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debugobjects.c debugobjects: insulate non-fixup logic related to static obj from fixup callbacks 2016-05-19 19:12:14 -07:00
dec_and_lock.c
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decompress.c lib/decompress: set the compressor name to NULL on error 2015-07-17 16:39:54 -07:00
decompress_bunzip2.c lib/decompressors: use real out buf size for gunzip with kernel 2015-09-10 13:29:01 -07:00
decompress_inflate.c lib/decompressors: use real out buf size for gunzip with kernel 2015-09-10 13:29:01 -07:00
decompress_unlz4.c lib/decompressors: use real out buf size for gunzip with kernel 2015-09-10 13:29:01 -07:00
decompress_unlzma.c lib/decompress_unlzma: Do a NULL check for pointer 2015-09-10 13:29:01 -07:00
decompress_unlzo.c lib/decompressors: use real out buf size for gunzip with kernel 2015-09-10 13:29:01 -07:00
decompress_unxz.c lib/decompressors: use real out buf size for gunzip with kernel 2015-09-10 13:29:01 -07:00
devres.c devres: use to_pci_dev() 2016-02-07 23:17:59 -08:00
digsig.c KEYS: Merge the type-specific data with the payload data 2015-10-21 15:18:36 +01:00
div64.c __div64_32(): make it overridable at compile time 2015-11-16 14:42:12 -05:00
dma-debug.c dma-debug: switch check from _text to _stext 2016-01-14 16:00:49 -08:00
dma-noop.c dma: Provide simple noop dma ops 2016-03-02 17:01:55 +02:00
dump_stack.c dump_stack: avoid potential deadlocks 2016-02-05 18:10:40 -08:00
dynamic_debug.c convert a bunch of open-coded instances of memdup_user_nul() 2016-01-04 10:26:58 -05:00
dynamic_queue_limits.c lib/dynamic_queue_limits.c: simplify includes 2015-02-12 18:54:15 -08:00
earlycpio.c
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extable.c extable: add support for relative extables to search and sort routines 2016-02-24 14:57:26 +00:00
fault-inject.c fault-inject: fix inverted interval/probability values in printk 2015-10-23 17:55:10 +09:00
fdt.c
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fdt_empty_tree.c lib: add fdt_empty_tree.c 2014-04-30 19:49:37 +01:00
fdt_ro.c
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fdt_rw.c
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fdt_strerror.c
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fdt_sw.c
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fdt_wip.c
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find_bit.c lib: rename lib/find_next_bit.c to lib/find_bit.c 2015-04-17 09:03:54 -04:00
flex_array.c
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flex_proportions.c lib+mm: fix few spelling mistakes 2016-02-15 11:18:23 +01:00
gcd.c
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gen_crc32table.c lib: crc32: constify crc32 lookup table 2015-02-13 21:21:35 -08:00
genalloc.c CPM/QE: use genalloc to manage CPM/QE muram 2015-12-22 17:10:18 -06:00
glob.c lib/glob.c: add CONFIG_GLOB_SELFTEST 2014-08-06 18:01:25 -07:00
halfmd4.c lib/halfmd4.c: use rol32 inline function in the ROUND macro 2015-11-06 17:50:42 -08:00
hexdump.c lib/hexdump.c: truncate output in case of overflow 2015-11-06 17:50:42 -08:00
hweight.c Make ARCH_HAS_FAST_MULTIPLIER a real config variable 2014-09-13 11:14:53 -07:00
idr.c mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd 2015-11-06 17:50:42 -08:00
inflate.c
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int_sqrt.c
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interval_tree.c lib/interval_tree.c: simplify includes 2015-02-12 18:54:15 -08:00
interval_tree_test.c lib: Export interval_tree 2014-05-05 09:09:14 +02:00
iomap.c Kconfig: rename HAS_IOPORT to HAS_IOPORT_MAP 2014-04-07 16:36:11 -07:00
iomap_copy.c lib/iomap_copy.c: add __ioread32_copy() 2016-01-20 17:09:18 -08:00
iommu-common.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc 2015-11-05 16:34:48 -08:00
iommu-helper.c
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ioremap.c x86, mm: support huge KVA mappings on x86 2015-04-14 16:49:04 -07:00
iov_iter.c Merge branch 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2016-05-18 11:46:23 -07:00
irq_poll.c irq_poll: Fix irq_poll_sched() 2016-01-19 15:26:55 -05:00
irq_regs.c
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is_single_threaded.c lib/is_single_threaded.c: change current_is_single_threaded() to use for_each_thread() 2015-11-06 17:50:42 -08:00
jedec_ddr_data.c
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kasprintf.c lib/kasprintf.c: add sanity check to kvasprintf 2016-01-16 11:17:27 -08:00
kfifo.c kfifo: use BUG_ON 2014-08-08 15:57:25 -07:00
klist.c klist: fix starting point removed bug in klist iterators 2016-02-07 22:18:47 -08:00
kobject.c kobject: export kset_find_obj() for module use 2016-02-09 17:36:34 -08:00
kobject_uevent.c lib/kobject_uevent.c: remove redundant include 2015-02-12 18:54:15 -08:00
kstrtox.c lib: add "on"/"off" support to kstrtobool 2016-03-17 15:09:34 -07:00
kstrtox.h
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lcm.c block: fix blk_stack_limits() regression due to lcm() change 2015-03-31 09:45:50 -06:00
libcrc32c.c Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2016-01-22 11:58:43 -08:00
list_debug.c list: kill list_force_poison() 2016-03-09 15:43:42 -08:00
list_sort.c lib/list_sort: use late_initcall to hook in self tests 2015-06-16 14:12:35 -04:00
llist.c lib/llist.c: fix data race in llist_del_first 2015-11-06 17:50:42 -08:00
locking-selftest-hardirq.h
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locking-selftest-mutex.h
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locking-selftest-rlock-hardirq.h
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locking-selftest-rlock-softirq.h
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locking-selftest-rlock.h
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locking-selftest-rsem.h
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locking-selftest-softirq.h
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locking-selftest-spin-hardirq.h
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locking-selftest-spin-softirq.h
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locking-selftest-spin.h
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locking-selftest-wlock-hardirq.h
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locking-selftest-wlock-softirq.h
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locking-selftest-wlock.h
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locking-selftest-wsem.h
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locking-selftest.c locking/lockdep: Revert qrwlock recusive stuff 2014-10-03 06:09:30 +02:00
lockref.c locking/lockref: Remove homebrew cmpxchg64_relaxed() macro definition 2015-08-12 11:59:04 +02:00
lru_cache.c lru_cache: Converted lc_seq_printf_status to return void 2015-11-25 09:22:02 -07:00
md5.c lib/md5.c: simplify include 2015-02-12 18:54:15 -08:00
memory-notifier-error-inject.c
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memweight.c
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net_utils.c mac_pton: Use bool not int return 2014-06-25 17:45:43 -07:00
netdev-notifier-error-inject.c net: Add support for CHANGEUPPER notifier error injection 2015-12-03 11:49:23 -05:00
nlattr.c libnl: fix help of _64bit functions 2016-04-23 20:13:24 -04:00
nmi_backtrace.c printk/nmi: generic solution for safe printk in NMI 2016-05-20 17:58:30 -07:00
nodemask.c include/linux/nodemask.h: create next_node_in() helper 2016-05-19 19:12:14 -07:00
notifier-error-inject.c
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notifier-error-inject.h
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of-reconfig-notifier-error-inject.c
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oid_registry.c
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once.c once: make helper generic for calling functions once 2015-10-08 05:26:36 -07:00
parser.c
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pci_iomap.c libnvdimm for 4.3: 2015-09-08 14:35:59 -07:00
percpu-refcount.c lib+mm: fix few spelling mistakes 2016-02-15 11:18:23 +01:00
percpu_counter.c percpu_counter: update debugobjects fixup callbacks return type 2016-05-19 19:12:14 -07:00
percpu_ida.c mm, page_alloc: rename __GFP_WAIT to __GFP_RECLAIM 2015-11-06 17:50:42 -08:00
percpu_test.c
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plist.c lib/plist.c: remove redundant include 2015-02-12 18:54:16 -08:00
pm-notifier-error-inject.c
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radix-tree.c radix_tree: add radix_tree_dump 2016-03-17 15:09:34 -07:00
random32.c netfilter: meta: add PRANDOM support 2016-02-29 13:55:59 +01:00
ratelimit.c ratelimit: fix bug in time interval by resetting right begin time 2016-01-21 17:20:51 -08:00
rational.c
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rbtree.c rbtree: Make lockless searches non-fatal 2015-05-28 11:32:04 +09:30
rbtree_test.c
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reciprocal_div.c
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rhashtable.c rhashtable: accept GFP flags in rhashtable_walk_init 2016-04-05 10:56:32 +02:00
scatterlist.c scatterlist: fix a typo in comment block of sg_miter_stop() 2016-02-08 10:15:17 -08:00
seq_buf.c tracing: Use seq_buf_used() in seq_buf_to_user() instead of len 2015-12-23 14:27:20 -05:00
sg_pool.c lib: scatterlist: move SG pool code from SCSI driver to lib/sg_pool.c 2016-04-15 16:53:14 -04:00
sg_split.c lib: scatterlist: add sg splitting function 2015-08-24 14:28:01 -06:00
sha1.c lib: EXPORT_SYMBOL sha_init 2015-03-23 22:12:08 -04:00
show_mem.c lib/show_mem.c: correct reserved memory calculation 2015-09-08 15:35:28 -07:00
smp_processor_id.c percpu: add preemption checks to __this_cpu ops 2014-04-07 16:36:14 -07:00
sort.c lib/sort: Add 64 bit swap function 2015-06-25 17:00:40 -07:00
stackdepot.c lib/stackdepot: avoid to return 0 handle 2016-05-05 17:38:53 -07:00
stmp_device.c lib/stmp_device.c: replace module.h include 2015-02-12 18:54:16 -08:00
string.c lib: move strtobool() to kstrtobool() 2016-03-17 15:09:34 -07:00
string_helpers.c string_helpers: add kstrdup_quotable_file 2016-04-21 10:47:26 +10:00
strncpy_from_user.c x86/kasan: instrument user memory access API 2016-05-20 17:58:30 -07:00
strnlen_user.c Use the new batched user accesses in generic user string handling 2015-12-17 10:05:19 -08:00
swiotlb.c Merge branch 'for-4.2/sg' of git://git.kernel.dk/linux-block 2015-06-25 15:22:36 -07:00
syscall.c lib/syscall.c: unexport task_current_syscall() 2014-04-03 16:21:06 -07:00
test-kstrtox.c kstrto*: accept "-0" for signed conversion 2015-09-10 13:29:01 -07:00
test-string_helpers.c lib/test-string_helpers.c: fix and improve string_get_size() tests 2016-02-03 08:28:43 -08:00
test_bitmap.c test_bitmap: unit tests for lib/bitmap.c 2016-02-19 22:54:09 -05:00
test_bpf.c bpf: prepare bpf_int_jit_compile/bpf_prog_select_runtime apis 2016-05-16 13:49:32 -04:00
test_firmware.c test: firmware_class: add asynchronous request trigger 2016-01-07 13:44:22 -07:00
test_hexdump.c test_hexdump: print statistics at the end 2016-01-20 17:09:18 -08:00
test_kasan.c kasan/tests: add tests for user memory access functions 2016-05-20 17:58:30 -07:00
test_module.c
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test_printf.c mm, printk: introduce new format string for flags 2016-03-15 16:55:16 -07:00
test_rhashtable.c rhashtable: accept GFP flags in rhashtable_walk_init 2016-04-05 10:56:32 +02:00
test_static_key_base.c locking/static_keys: Provide a selftest 2015-08-03 11:51:12 +02:00
test_static_keys.c locking/static_keys: Avoid nested functions 2016-02-09 10:27:29 +01:00
test_user_copy.c
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textsearch.c lib/textsearch.c: remove textsearch_put reference from comments 2014-10-14 02:18:14 +02:00
timerqueue.c timerqueue: Let timerqueue_add/del return information 2015-04-22 17:06:49 +02:00
ts_bm.c
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ts_fsm.c
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ts_kmp.c
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ubsan.c UBSAN: run-time undefined behavior sanity checker 2016-01-20 17:09:18 -08:00
ubsan.h UBSAN: run-time undefined behavior sanity checker 2016-01-20 17:09:18 -08:00
ucs2_string.c lib/ucs2_string: Correct ucs2 -> utf8 conversion 2016-02-16 12:49:05 +00:00
usercopy.c
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uuid.c
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vsprintf.c sscanf: implement basic character sets 2016-03-17 15:09:34 -07:00