The patch titled
Subject: kernel/locking/lockdep.c: make lockdep initialize itself on demand
has been added to the -mm tree. Its filename is
kernel-locking-lockdepc-make-lockdep-initialize-itself-on-demand.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kernel-locking-lockdepc-make-lockdep-initialize-itself-on-demand.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kernel-locking-lockdepc-make-lockdep-initialize-itself-on-demand.patch
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From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: kernel/locking/lockdep.c: make lockdep initialize itself on demand
Mike said:
: CONFIG_UBSAN_ALIGNMENT breaks x86-64 kernel with lockdep enabled, i. e
: kernel with CONFIG_UBSAN_ALIGNMENT fails to load without even any error
: message.
:
: The problem is that ubsan callbacks use spinlocks and might be called
: before lockdep is initialized. Particularly this line in the
: reserve_ebda_region function causes problem:
:
: lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES);
:
: If i put lockdep_init() before reserve_ebda_region call in
: x86_64_start_reservations kernel loads well.
Fix this ordering issue permanently: change lockdep so that it ensures
that the hash tables are initialized when they are about to be used.
The overhead will be pretty small: a test-n-branch in places where lockdep
is about to do a lot of work anyway.
Possibly lockdep_initialized should be made __read_mostly.
A better fix would be to simply initialize these (32768 entry) arrays of
empty list_heads at compile time, but I don't think there's a way of
teaching gcc to do this.
We could write a little script which, at compile time, emits a file
containing
[0] = LIST_HEAD_INIT(__chainhash_table[0]),
[1] = LIST_HEAD_INIT(__chainhash_table[1]),
...
[32767] = LIST_HEAD_INIT(__chainhash_table[32767]),
and then #include this file into lockdep.c. Sounds like a lot of fuss.
Reported-by: Mike Krinkin <krinkin.m.u@xxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/locking/lockdep.c | 35 ++++++++++++++++++++++++++---------
1 file changed, 26 insertions(+), 9 deletions(-)
diff -puN kernel/locking/lockdep.c~kernel-locking-lockdepc-make-lockdep-initialize-itself-on-demand kernel/locking/lockdep.c
--- a/kernel/locking/lockdep.c~kernel-locking-lockdepc-make-lockdep-initialize-itself-on-demand
+++ a/kernel/locking/lockdep.c
@@ -290,9 +290,20 @@ LIST_HEAD(all_lock_classes);
#define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
#define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
#define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
-#define classhashentry(key) (classhash_table + __classhashfn((key)))
-static struct list_head classhash_table[CLASSHASH_SIZE];
+static struct list_head __classhash_table[CLASSHASH_SIZE];
+
+static inline struct list_head *get_classhash_table(void)
+{
+ if (unlikely(!lockdep_initialized))
+ lockdep_init();
+ return __classhash_table;
+}
+
+static inline struct list_head *classhashentry(struct lockdep_subclass_key *key)
+{
+ return get_classhash_table() + __classhashfn(key);
+}
/*
* We put the lock dependency chains into a hash-table as well, to cache
@@ -301,9 +312,15 @@ static struct list_head classhash_table[
#define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
#define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
#define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
-#define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
-static struct list_head chainhash_table[CHAINHASH_SIZE];
+static struct list_head __chainhash_table[CHAINHASH_SIZE];
+
+static struct list_head *chainhashentry(unsigned long chain)
+{
+ if (unlikely(!lockdep_initialized))
+ lockdep_init();
+ return __chainhash_table + __chainhashfn(chain);
+}
/*
* The hash key of the lock dependency chains is a hash itself too:
@@ -3875,7 +3892,7 @@ void lockdep_reset(void)
nr_process_chains = 0;
debug_locks = 1;
for (i = 0; i < CHAINHASH_SIZE; i++)
- INIT_LIST_HEAD(chainhash_table + i);
+ INIT_LIST_HEAD(__chainhash_table + i);
raw_local_irq_restore(flags);
}
@@ -3929,7 +3946,7 @@ void lockdep_free_key_range(void *start,
* Unhash all classes that were created by this module:
*/
for (i = 0; i < CLASSHASH_SIZE; i++) {
- head = classhash_table + i;
+ head = get_classhash_table() + i;
if (list_empty(head))
continue;
list_for_each_entry_rcu(class, head, hash_entry) {
@@ -3986,7 +4003,7 @@ void lockdep_reset_lock(struct lockdep_m
*/
locked = graph_lock();
for (i = 0; i < CLASSHASH_SIZE; i++) {
- head = classhash_table + i;
+ head = get_classhash_table() + i;
if (list_empty(head))
continue;
list_for_each_entry_rcu(class, head, hash_entry) {
@@ -4027,10 +4044,10 @@ void lockdep_init(void)
return;
for (i = 0; i < CLASSHASH_SIZE; i++)
- INIT_LIST_HEAD(classhash_table + i);
+ INIT_LIST_HEAD(__classhash_table + i);
for (i = 0; i < CHAINHASH_SIZE; i++)
- INIT_LIST_HEAD(chainhash_table + i);
+ INIT_LIST_HEAD(__chainhash_table + i);
lockdep_initialized = 1;
}
_
Patches currently in -mm which might be from akpm@xxxxxxxxxxxxxxxxxxxx are
i-need-old-gcc.patch
arch-alpha-kernel-systblss-remove-debug-check.patch
drivers-gpu-drm-i915-intel_spritec-fix-build.patch
drivers-gpu-drm-i915-intel_tvc-fix-build.patch
arm-arch-arm-include-asm-pageh-needs-personalityh.patch
mm-warn-about-vmdata-over-rlimit_data-fix.patch
ocfs2-code-clean-up-for-direct-io-fix.patch
ocfs2-fix-ip_unaligned_aio-deadlock-with-dio-work-queue-fix.patch
ocfs2-dlm-move-lock-to-the-tail-of-grant-queue-while-doing-in-place-convert-fix.patch
kernel-locking-lockdepc-make-lockdep-initialize-itself-on-demand.patch
mm.patch
mm-slab-put-the-freelist-at-the-end-of-slab-page-fix.patch
fs-mpagec-mpage_readpages-use-lru_to_page-helper.patch
mm-page_allocc-introduce-kernelcore=mirror-option-fix.patch
mm-page_allocc-rework-code-layout-in-memmap_init_zone.patch
mm-debug-pageallocc-split-out-page-poisoning-from-debug-page_alloc-checkpatch-fixes.patch
mm-page_poisonc-enable-page_poisoning-as-a-separate-option-fix.patch
mm-page_poisoningc-allow-for-zero-poisoning-checkpatch-fixes.patch
mm-madvise-update-comment-on-sys_madvise-fix.patch
ksm-introduce-ksm_max_page_sharing-per-page-deduplication-limit-fix-2.patch
zram-export-the-number-of-available-comp-streams-fix.patch
mm-oom-rework-oom-detection-checkpatch-fixes.patch
mm-use-watermak-checks-for-__gfp_repeat-high-order-allocations-checkpatch-fixes.patch
sched-add-schedule_timeout_idle.patch
btrfs-use-radix_tree_iter_retry-fix.patch
sparc-compat-provide-an-accurate-in_compat_syscall-implementation-fix.patch
sparc-compat-provide-an-accurate-in_compat_syscall-implementation-fix-fix.patch
dma-rename-dma__writecombine-to-dma__wc-checkpatch-fixes.patch
linux-next-git-rejects.patch
drivers-net-wireless-intel-iwlwifi-dvm-calibc-fix-min-warning.patch
include-linux-huge_mmh-pmd_trans_huge_lock-returns-a-spinlock_t.patch
do_shared_fault-check-that-mmap_sem-is-held.patch
kernel-forkc-export-kernel_thread-to-modules.patch
slab-leaks3-default-y.patch
kernel-locking-lockdepc-make-lockdep-initialize-itself-on-demand-fix.patch
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