* [PATCH] lglock: Use spinlock_t instead of arch_spinlock_t
@ 2015-03-26 15:02 Daniel Wagner
2015-03-26 16:03 ` Peter Zijlstra
0 siblings, 1 reply; 4+ messages in thread
From: Daniel Wagner @ 2015-03-26 15:02 UTC (permalink / raw)
To: Jeff Layton, Peter Zijlstra, Ingo Molnar
Cc: Daniel Wagner, Alexander Viro, J. Bruce Fields, Thomas Gleixner,
Andi Kleen, linux-fsdevel, linux-kernel
arch_spinlock_t is the most low level spinlock type. lglock is not
depending on arch_spinlock_t type and works also fine with normal
spinlock_t. So there is no need to use it outside of the archicture
code.
There are two users of lglock which is fs/locks.c and
kernel/stop_machine.c. The later doesn't depend on performance. So
here some numbers for fs/locks.c only.
Running all tests from lockperf 100 times on a 4 socket machine,
Intel(R) Xeon(R) CPU E5-4610 v2 @ 2.30GHz.
flock01 -n 128 -l 128
mean variance sigma max min
4.0.0-rc5 448.0287 15417.8359 124.1686 527.8083 0.0081
4.0.0-rc5-spinlocks_t 395.1646 28713.4347 169.4504 520.7507 0.0075
flock02 -n 256 -l 20480
mean variance sigma max min
4.0.0-rc5 6.9185 0.8830 0.9397 10.6138 4.9707
4.0.0-rc5-spinlocks_t 6.2474 0.9234 0.9610 9.5478 4.3703
lease01 -n 128 -l 128
mean variance sigma max min
4.0.0-rc5 7.7040 0.3930 0.6269 9.1874 5.4179
4.0.0-rc5-spinlocks_t 7.6862 0.7794 0.8828 9.0623 1.3639
lease02 -n 128 -l 512
mean variance sigma max min
4.0.0-rc5 16.3074 0.1418 0.3766 17.1600 15.0240
4.0.0-rc5-spinlocks_t 16.2698 0.2772 0.5265 17.2221 13.4127
posix01 -n 128 -l 128
mean variance sigma max min
4.0.0-rc5 531.5151 181.3078 13.4651 596.5883 501.2940
4.0.0-rc5-spinlocks_t 531.3600 209.0023 14.4569 600.7317 507.1767
posix02 -n 256 -l 20480
mean variance sigma max min
4.0.0-rc5 13.8395 2.9768 1.7253 22.0783 9.9136
4.0.0-rc5-spinlocks_t 12.6822 3.1645 1.7789 18.1258 9.0030
posix03 -n 512 -i 128
mean variance sigma max min
4.0.0-rc5 0.8939 0.0006 0.0242 0.9392 0.8360
4.0.0-rc5-spinlocks_t 0.9050 0.0006 0.0254 0.9617 0.8454
posix04 -n 64 -i 32
mean variance sigma max min
4.0.0-rc5 0.0122 0.0000 0.0023 0.0227 0.0083
4.0.0-rc5-spinlocks_t 0.0115 0.0000 0.0016 0.0165 0.0091
This also makes -rt a bit more happy place since normal spinlocks_t can sleep with
PREEMPT_RT=y.
Link: https://git.samba.org/jlayton/linux.git/?p=jlayton/lockperf.git;a=summary
Link: https://lwn.net/Articles/365863/
Link: http://marc.info/?l=linux-kernel&m=142737586415051&w=2
Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Jeff Layton <jlayton@poochiereds.net>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
include/linux/lglock.h | 10 +++++-----
kernel/locking/lglock.c | 24 ++++++++++++------------
2 files changed, 17 insertions(+), 17 deletions(-)
diff --git a/include/linux/lglock.h b/include/linux/lglock.h
index 0081f00..ea97f74 100644
--- a/include/linux/lglock.h
+++ b/include/linux/lglock.h
@@ -34,7 +34,7 @@
#endif
struct lglock {
- arch_spinlock_t __percpu *lock;
+ spinlock_t __percpu *lock;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lock_class_key lock_key;
struct lockdep_map lock_dep_map;
@@ -42,13 +42,13 @@ struct lglock {
};
#define DEFINE_LGLOCK(name) \
- static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \
- = __ARCH_SPIN_LOCK_UNLOCKED; \
+ static DEFINE_PER_CPU(spinlock_t, name ## _lock) \
+ = __SPIN_LOCK_UNLOCKED(name ## _lock); \
struct lglock name = { .lock = &name ## _lock }
#define DEFINE_STATIC_LGLOCK(name) \
- static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \
- = __ARCH_SPIN_LOCK_UNLOCKED; \
+ static DEFINE_PER_CPU(spinlock_t, name ## _lock) \
+ = __SPIN_LOCK_UNLOCKED(name ## _lock); \
static struct lglock name = { .lock = &name ## _lock }
void lg_lock_init(struct lglock *lg, char *name);
diff --git a/kernel/locking/lglock.c b/kernel/locking/lglock.c
index 86ae2ae..34077a7 100644
--- a/kernel/locking/lglock.c
+++ b/kernel/locking/lglock.c
@@ -18,44 +18,44 @@ EXPORT_SYMBOL(lg_lock_init);
void lg_local_lock(struct lglock *lg)
{
- arch_spinlock_t *lock;
+ spinlock_t *lock;
preempt_disable();
lock_acquire_shared(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
lock = this_cpu_ptr(lg->lock);
- arch_spin_lock(lock);
+ spin_lock(lock);
}
EXPORT_SYMBOL(lg_local_lock);
void lg_local_unlock(struct lglock *lg)
{
- arch_spinlock_t *lock;
+ spinlock_t *lock;
lock_release(&lg->lock_dep_map, 1, _RET_IP_);
lock = this_cpu_ptr(lg->lock);
- arch_spin_unlock(lock);
+ spin_unlock(lock);
preempt_enable();
}
EXPORT_SYMBOL(lg_local_unlock);
void lg_local_lock_cpu(struct lglock *lg, int cpu)
{
- arch_spinlock_t *lock;
+ spinlock_t *lock;
preempt_disable();
lock_acquire_shared(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
lock = per_cpu_ptr(lg->lock, cpu);
- arch_spin_lock(lock);
+ spin_lock(lock);
}
EXPORT_SYMBOL(lg_local_lock_cpu);
void lg_local_unlock_cpu(struct lglock *lg, int cpu)
{
- arch_spinlock_t *lock;
+ spinlock_t *lock;
lock_release(&lg->lock_dep_map, 1, _RET_IP_);
lock = per_cpu_ptr(lg->lock, cpu);
- arch_spin_unlock(lock);
+ spin_unlock(lock);
preempt_enable();
}
EXPORT_SYMBOL(lg_local_unlock_cpu);
@@ -67,9 +67,9 @@ void lg_global_lock(struct lglock *lg)
preempt_disable();
lock_acquire_exclusive(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
for_each_possible_cpu(i) {
- arch_spinlock_t *lock;
+ spinlock_t *lock;
lock = per_cpu_ptr(lg->lock, i);
- arch_spin_lock(lock);
+ spin_lock(lock);
}
}
EXPORT_SYMBOL(lg_global_lock);
@@ -80,9 +80,9 @@ void lg_global_unlock(struct lglock *lg)
lock_release(&lg->lock_dep_map, 1, _RET_IP_);
for_each_possible_cpu(i) {
- arch_spinlock_t *lock;
+ spinlock_t *lock;
lock = per_cpu_ptr(lg->lock, i);
- arch_spin_unlock(lock);
+ spin_unlock(lock);
}
preempt_enable();
}
--
2.1.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] lglock: Use spinlock_t instead of arch_spinlock_t
2015-03-26 15:02 [PATCH] lglock: Use spinlock_t instead of arch_spinlock_t Daniel Wagner
@ 2015-03-26 16:03 ` Peter Zijlstra
2015-03-30 6:07 ` Daniel Wagner
0 siblings, 1 reply; 4+ messages in thread
From: Peter Zijlstra @ 2015-03-26 16:03 UTC (permalink / raw)
To: Daniel Wagner
Cc: Jeff Layton, Ingo Molnar, Alexander Viro, J. Bruce Fields,
Thomas Gleixner, Andi Kleen, linux-fsdevel, linux-kernel
On Thu, Mar 26, 2015 at 04:02:08PM +0100, Daniel Wagner wrote:
> @@ -67,9 +67,9 @@ void lg_global_lock(struct lglock *lg)
> preempt_disable();
> lock_acquire_exclusive(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
> for_each_possible_cpu(i) {
> - arch_spinlock_t *lock;
> + spinlock_t *lock;
> lock = per_cpu_ptr(lg->lock, i);
> - arch_spin_lock(lock);
> + spin_lock(lock);
> }
> }
Nope, that'll blow up in two separate places.
One: lockdep, it can only track a limited number of held locks, and it
will further report a recursion warning on the 2nd cpu.
Second: preempt_count_add(), spin_lock() does preempt_disable(), with
enough CPUs you'll overflow the preempt counter (255).
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] lglock: Use spinlock_t instead of arch_spinlock_t
2015-03-26 16:03 ` Peter Zijlstra
@ 2015-03-30 6:07 ` Daniel Wagner
2015-03-31 9:17 ` Ingo Molnar
0 siblings, 1 reply; 4+ messages in thread
From: Daniel Wagner @ 2015-03-30 6:07 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Jeff Layton, Ingo Molnar, Alexander Viro, J. Bruce Fields,
Thomas Gleixner, Andi Kleen, linux-fsdevel, linux-kernel
On 03/26/2015 05:03 PM, Peter Zijlstra wrote:
> On Thu, Mar 26, 2015 at 04:02:08PM +0100, Daniel Wagner wrote:
>> @@ -67,9 +67,9 @@ void lg_global_lock(struct lglock *lg)
>> preempt_disable();
>> lock_acquire_exclusive(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
>> for_each_possible_cpu(i) {
>> - arch_spinlock_t *lock;
>> + spinlock_t *lock;
>> lock = per_cpu_ptr(lg->lock, i);
>> - arch_spin_lock(lock);
>> + spin_lock(lock);
>> }
>> }
>
> Nope, that'll blow up in two separate places.
>
> One: lockdep, it can only track a limited number of held locks, and it
> will further report a recursion warning on the 2nd cpu.
I was wondering why I haven't seen it explode. As it turns out I haven't
looked closely enough at dmesg:
[ +0.001231] BUG: MAX_LOCK_DEPTH too low!
[ +0.000092] turning off the locking correctness validator.
[ +0.000092] Please attach the output of /proc/lock_stat to the bug report
[ +0.000094] depth: 48 max: 48!
[ +0.000087] 48 locks held by swapper/0/1:
[ +0.000090] #0: (cpu_hotplug.lock){++++++}, at: [<ffffffff8109e767>] get_online_cpus+0x37/0x80
[ +0.000503] #1: (stop_cpus_mutex){+.+...}, at: [<ffffffff8114b889>] stop_cpus+0x29/0x60
[ +0.000504] #2: (stop_cpus_lock){+.+...}, at: [<ffffffff8114b2de>] queue_stop_cpus_work+0x7e/0xd0
[ +0.000582] #3: (stop_cpus_lock_lock){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.000496] #4: (stop_cpus_lock_lock#2){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.000577] #5: (stop_cpus_lock_lock#3){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.000581] #6: (stop_cpus_lock_lock#4){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.000576] #7: (stop_cpus_lock_lock#5){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.000576] #8: (stop_cpus_lock_lock#6){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.000575] #9: (stop_cpus_lock_lock#7){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.000817] #10: (stop_cpus_lock_lock#8){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001057] #11: (stop_cpus_lock_lock#9){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001057] #12: (stop_cpus_lock_lock#10){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001055] #13: (stop_cpus_lock_lock#11){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001059] #14: (stop_cpus_lock_lock#12){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001056] #15: (stop_cpus_lock_lock#13){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001054] #16: (stop_cpus_lock_lock#14){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001053] #17: (stop_cpus_lock_lock#15){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001052] #18: (stop_cpus_lock_lock#16){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001059] #19: (stop_cpus_lock_lock#17){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001072] #20: (stop_cpus_lock_lock#18){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001057] #21: (stop_cpus_lock_lock#19){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001060] #22: (stop_cpus_lock_lock#20){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001060] #23: (stop_cpus_lock_lock#21){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001060] #24: (stop_cpus_lock_lock#22){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001065] #25: (stop_cpus_lock_lock#23){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001055] #26: (stop_cpus_lock_lock#24){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001058] #27: (stop_cpus_lock_lock#25){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001055] #28: (stop_cpus_lock_lock#26){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001054] #29: (stop_cpus_lock_lock#27){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001052] #30: (stop_cpus_lock_lock#28){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001059] #31: (stop_cpus_lock_lock#29){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001056] #32: (stop_cpus_lock_lock#30){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001149] #33: (stop_cpus_lock_lock#31){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001060] #34: (stop_cpus_lock_lock#32){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001063] #35: (stop_cpus_lock_lock#33){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001064] #36: (stop_cpus_lock_lock#34){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001061] #37: (stop_cpus_lock_lock#35){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001054] #38: (stop_cpus_lock_lock#36){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001059] #39: (stop_cpus_lock_lock#37){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001059] #40: (stop_cpus_lock_lock#38){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001057] #41: (stop_cpus_lock_lock#39){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001056] #42: (stop_cpus_lock_lock#40){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001055] #43: (stop_cpus_lock_lock#41){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001055] #44: (stop_cpus_lock_lock#42){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001059] #45: (stop_cpus_lock_lock#43){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001051] #46: (stop_cpus_lock_lock#44){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001123] #47: (stop_cpus_lock_lock#45){+.+...}, at: [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.001058] INFO: lockdep is turned off.
[ +0.000330] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.0.0-rc5-00001-g70ed1b1 #31
[ +0.000581] Hardware name: Dell Inc. PowerEdge R820/066N7P, BIOS 2.0.20 01/16/2014
[ +0.000582] 0000000000000000 000000002752ae20 ffff881fb119ba88 ffffffff817dcbc1
[ +0.000895] 0000000000000000 ffff885fb14f8000 ffff881fb119bb88 ffffffff810ed5aa
[ +0.000899] ffffffff82885150 ffff885fb14f8000 0000000000000292 0000000000000000
[ +0.000893] Call Trace:
[ +0.000329] [<ffffffff817dcbc1>] dump_stack+0x4c/0x65
[ +0.000333] [<ffffffff810ed5aa>] __lock_acquire+0xfca/0x1f90
[ +0.000334] [<ffffffff8110f72f>] ? rcu_irq_exit+0x7f/0xd0
[ +0.000333] [<ffffffff817e766c>] ? retint_restore_args+0x13/0x13
[ +0.000335] [<ffffffff810ef5a7>] lock_acquire+0xc7/0x160
[ +0.000334] [<ffffffff810f2af6>] ? lg_global_lock+0x66/0x90
[ +0.000334] [<ffffffff8114b130>] ? cpu_stop_should_run+0x50/0x50
[ +0.000335] [<ffffffff817e59dd>] _raw_spin_lock+0x3d/0x80
[ +0.000336] [<ffffffff810f2af6>] ? lg_global_lock+0x66/0x90
[ +0.000335] [<ffffffff810f2af6>] lg_global_lock+0x66/0x90
[ +0.000333] [<ffffffff8114b2de>] ? queue_stop_cpus_work+0x7e/0xd0
[ +0.000338] [<ffffffff8114b2de>] queue_stop_cpus_work+0x7e/0xd0
[ +0.000335] [<ffffffff8114b130>] ? cpu_stop_should_run+0x50/0x50
[ +0.000337] [<ffffffff8114b538>] __stop_cpus+0x58/0xa0
[ +0.000335] [<ffffffff8114b130>] ? cpu_stop_should_run+0x50/0x50
[ +0.000334] [<ffffffff8114b130>] ? cpu_stop_should_run+0x50/0x50
[ +0.000335] [<ffffffff8114b897>] stop_cpus+0x37/0x60
[ +0.000339] [<ffffffff810444e0>] ? mtrr_restore+0xb0/0xb0
[ +0.000337] [<ffffffff8114ba15>] __stop_machine+0xf5/0x130
[ +0.000334] [<ffffffff810444e0>] ? mtrr_restore+0xb0/0xb0
[ +0.000334] [<ffffffff810444e0>] ? mtrr_restore+0xb0/0xb0
[ +0.000337] [<ffffffff8114ba7e>] stop_machine+0x2e/0x50
[ +0.000330] [<ffffffff81044efb>] mtrr_aps_init+0x7b/0x90
[ +0.000433] [<ffffffff81f3faac>] native_smp_cpus_done+0x10b/0x113
[ +0.000335] [<ffffffff81f51d74>] smp_init+0x78/0x80
[ +0.000332] [<ffffffff81f2d1e1>] kernel_init_freeable+0x167/0x28d
[ +0.000336] [<ffffffff817d2690>] ? rest_init+0xd0/0xd0
[ +0.000334] [<ffffffff817d269e>] kernel_init+0xe/0xf0
[ +0.000336] [<ffffffff817e6918>] ret_from_fork+0x58/0x90
[ +0.000333] [<ffffffff817d2690>] ? rest_init+0xd0/0xd0
and after that lockdep is disabled. /me feeling extremely stupid.
> Second: preempt_count_add(), spin_lock() does preempt_disable(), with
> enough CPUs you'll overflow the preempt counter (255).
Thanks for the review.
cheers,
daniel
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] lglock: Use spinlock_t instead of arch_spinlock_t
2015-03-30 6:07 ` Daniel Wagner
@ 2015-03-31 9:17 ` Ingo Molnar
0 siblings, 0 replies; 4+ messages in thread
From: Ingo Molnar @ 2015-03-31 9:17 UTC (permalink / raw)
To: Daniel Wagner
Cc: Peter Zijlstra, Jeff Layton, Ingo Molnar, Alexander Viro,
J. Bruce Fields, Thomas Gleixner, Andi Kleen, linux-fsdevel,
linux-kernel
* Daniel Wagner <daniel.wagner@bmw-carit.de> wrote:
> On 03/26/2015 05:03 PM, Peter Zijlstra wrote:
> > On Thu, Mar 26, 2015 at 04:02:08PM +0100, Daniel Wagner wrote:
> >> @@ -67,9 +67,9 @@ void lg_global_lock(struct lglock *lg)
> >> preempt_disable();
> >> lock_acquire_exclusive(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
> >> for_each_possible_cpu(i) {
> >> - arch_spinlock_t *lock;
> >> + spinlock_t *lock;
> >> lock = per_cpu_ptr(lg->lock, i);
> >> - arch_spin_lock(lock);
> >> + spin_lock(lock);
> >> }
> >> }
> >
> > Nope, that'll blow up in two separate places.
> >
> > One: lockdep, it can only track a limited number of held locks, and it
> > will further report a recursion warning on the 2nd cpu.
>
> I was wondering why I haven't seen it explode. As it turns out I haven't
> looked closely enough at dmesg:
>
> [ +0.001231] BUG: MAX_LOCK_DEPTH too low!
> [ +0.000092] turning off the locking correctness validator.
Yeah, we try really hard to not crash the kernel from debugging code,
whenever we can avoid it! That sometimes creates a false sense of good
kernel health.
Thanks,
Ingo
^ permalink raw reply [flat|nested] 4+ messages in thread
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2015-03-26 15:02 [PATCH] lglock: Use spinlock_t instead of arch_spinlock_t Daniel Wagner
2015-03-26 16:03 ` Peter Zijlstra
2015-03-30 6:07 ` Daniel Wagner
2015-03-31 9:17 ` Ingo Molnar
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