diff mbox series

[v2,2/3] mm: Split unregister_shrinker() in fast and slow part

Message ID 168599179360.70911.4102140966715923751.stgit@pro.pro (mailing list archive)
State New, archived
Headers show
Series mm: Make unregistration of super_block shrinker more faster | expand

Commit Message

Kirill Tkhai June 5, 2023, 7:03 p.m. UTC 
This splits unregister_shrinker() in two parts, and this allows
to make the unregistration faster by moving the slow part
in delayed asynchronous work. Note, that the guarantees remain
the same: no do_shrink_slab() calls are possible after the first
part. This will be used in next patch.

Signed-off-by: Kirill Tkhai <tkhai@ya.ru>
---
 include/linux/shrinker.h |    4 ++++
 mm/vmscan.c              |   35 +++++++++++++++++++++++++++++------
 2 files changed, 33 insertions(+), 6 deletions(-)

Comments

kernel test robot June 7, 2023, 4:49 a.m. UTC | #1 
Hello,

kernel test robot noticed "INFO:trying_to_register_non-static_key" on:

commit: 107ed33204f77282d67b90f5c37f34c4b1ec9ffb ("[PATCH v2 2/3] mm: Split unregister_shrinker() in fast and slow part")
url: https://github.com/intel-lab-lkp/linux/commits/Kirill-Tkhai/mm-vmscan-move-shrinker_debugfs_remove-before-synchronize_srcu/20230606-030419
base: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git f8dba31b0a826e691949cd4fdfa5c30defaac8c5
patch link: https://lore.kernel.org/all/168599179360.70911.4102140966715923751.stgit@pro.pro/
patch subject: [PATCH v2 2/3] mm: Split unregister_shrinker() in fast and slow part

in testcase: boot

compiler: clang-15
test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 4G

(please refer to attached dmesg/kmsg for entire log/backtrace)



If you fix the issue, kindly add following tag
| Reported-by: kernel test robot <oliver.sang@intel.com>
| Closes: https://lore.kernel.org/oe-lkp/202306071000.4ad4e5ba-oliver.sang@intel.com


[    0.538549][    T0] INFO: trying to register non-static key.
[    0.539249][    T0] The code is fine but needs lockdep annotation, or maybe
[    0.539385][    T0] you didn't initialize this object before use?
[    0.539385][    T0] turning off the locking correctness validator.
[    0.539385][    T0] CPU: 0 PID: 0 Comm: swapper Not tainted 6.4.0-rc5-00004-g107ed33204f7 #1
[    0.539385][    T0] Call Trace:
[ 0.539385][ T0] dump_stack_lvl (??:?) 
[ 0.539385][ T0] dump_stack (??:?) 
[ 0.539385][ T0] assign_lock_key (lockdep.c:?) 
[ 0.539385][ T0] register_lock_class (lockdep.c:?) 
[ 0.539385][ T0] __lock_acquire (lockdep.c:?) 
[ 0.539385][ T0] ? lock_acquire (??:?) 
[ 0.539385][ T0] ? register_shrinker_prepared (??:?) 
[ 0.539385][ T0] ? __might_resched (??:?) 
[ 0.539385][ T0] lock_acquire (??:?) 
[ 0.539385][ T0] ? register_shrinker_prepared (??:?) 
[ 0.539385][ T0] ? __might_resched (??:?) 
[ 0.539385][ T0] down_write (??:?) 
[ 0.539385][ T0] ? register_shrinker_prepared (??:?) 
[ 0.539385][ T0] register_shrinker_prepared (??:?) 
[ 0.539385][ T0] sget_fc (??:?) 
[ 0.539385][ T0] ? kill_litter_super (??:?) 
[ 0.539385][ T0] ? shmem_reconfigure (shmem.c:?) 
[ 0.539385][ T0] get_tree_nodev (??:?) 
[ 0.539385][ T0] shmem_get_tree (shmem.c:?) 
[ 0.539385][ T0] vfs_get_tree (??:?) 
[ 0.539385][ T0] vfs_kern_mount (??:?) 
[ 0.539385][ T0] kern_mount (??:?) 
[ 0.539385][ T0] shmem_init (??:?) 
[ 0.539385][ T0] mnt_init (??:?) 
[ 0.539385][ T0] vfs_caches_init (??:?) 
[ 0.539385][ T0] start_kernel (??:?) 
[ 0.539385][ T0] i386_start_kernel (??:?) 
[ 0.539385][ T0] startup_32_smp (??:?) 
[    0.539391][    T0] ------------[ cut here ]------------
[    0.540097][    T0] DEBUG_RWSEMS_WARN_ON(sem->magic != sem): count = 0x1, magic = 0x0, owner = 0x81d77c00, curr 0x81d77c00, list not empty
[ 0.540405][ T0] WARNING: CPU: 0 PID: 0 at kernel/locking/rwsem.c:1364 up_write (??:?) 
[    0.541389][    T0] Modules linked in:
[    0.542390][    T0] CPU: 0 PID: 0 Comm: swapper Not tainted 6.4.0-rc5-00004-g107ed33204f7 #1
[ 0.543389][ T0] EIP: up_write (??:?) 
[ 0.543920][ T0] Code: ee 8f c6 81 39 c1 74 05 bb 7f 8b c4 81 53 52 ff 74 24 08 57 ff 74 24 14 68 44 a3 cb 81 68 6d 1a ce 81 e8 32 68 fb ff 83 c4 1c <0f> 0b 39 f7 0f 85 a8 fe ff ff e9 a8 fe ff ff 0f 0b e9 db fe ff ff
All code
========
   0:	ee                   	out    %al,(%dx)
   1:	8f c6                	pop    %rsi
   3:	81 39 c1 74 05 bb    	cmpl   $0xbb0574c1,(%rcx)
   9:	7f 8b                	jg     0xffffffffffffff96
   b:	c4 81 53 52          	(bad)  
   f:	ff 74 24 08          	pushq  0x8(%rsp)
  13:	57                   	push   %rdi
  14:	ff 74 24 14          	pushq  0x14(%rsp)
  18:	68 44 a3 cb 81       	pushq  $0xffffffff81cba344
  1d:	68 6d 1a ce 81       	pushq  $0xffffffff81ce1a6d
  22:	e8 32 68 fb ff       	callq  0xfffffffffffb6859
  27:	83 c4 1c             	add    $0x1c,%esp
  2a:*	0f 0b                	ud2    		<-- trapping instruction
  2c:	39 f7                	cmp    %esi,%edi
  2e:	0f 85 a8 fe ff ff    	jne    0xfffffffffffffedc
  34:	e9 a8 fe ff ff       	jmpq   0xfffffffffffffee1
  39:	0f 0b                	ud2    
  3b:	e9 db fe ff ff       	jmpq   0xffffffffffffff1b

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2    
   2:	39 f7                	cmp    %esi,%edi
   4:	0f 85 a8 fe ff ff    	jne    0xfffffffffffffeb2
   a:	e9 a8 fe ff ff       	jmpq   0xfffffffffffffeb7
   f:	0f 0b                	ud2    
  11:	e9 db fe ff ff       	jmpq   0xfffffffffffffef1
[    0.544391][    T0] EAX: e6de3575 EBX: 81c48b7f ECX: e6de3575 EDX: 81d67dd0
[    0.545388][    T0] ESI: 831f4c4c EDI: 00000000 EBP: 81d67ed0 ESP: 81d67ea8
[    0.546389][    T0] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 00210292
[    0.547388][    T0] CR0: 80050033 CR2: ffd98000 CR3: 02280000 CR4: 00040690
[    0.548392][    T0] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
[    0.549388][    T0] DR6: fffe0ff0 DR7: 00000400
[    0.549947][    T0] Call Trace:
[ 0.550391][ T0] ? show_regs (??:?) 
[ 0.550910][ T0] ? up_write (??:?) 
[ 0.551389][ T0] ? __warn (??:?) 
[ 0.551869][ T0] ? up_write (??:?) 
[ 0.552389][ T0] ? up_write (??:?) 
[ 0.552921][ T0] ? report_bug (??:?) 
[ 0.553390][ T0] ? exc_overflow (??:?) 
[ 0.554390][ T0] ? handle_bug (traps.c:?) 
[ 0.554923][ T0] ? exc_invalid_op (??:?) 
[ 0.555390][ T0] ? handle_exception (init_task.c:?) 
[ 0.556022][ T0] ? arch_report_meminfo (??:?) 
[ 0.556389][ T0] ? exc_overflow (??:?) 
[ 0.557389][ T0] ? up_write (??:?) 
[ 0.557927][ T0] ? exc_overflow (??:?) 
[ 0.558389][ T0] ? up_write (??:?) 
[ 0.558904][ T0] register_shrinker_prepared (??:?) 
[ 0.559390][ T0] sget_fc (??:?) 
[ 0.559887][ T0] ? kill_litter_super (??:?) 
[ 0.560390][ T0] ? shmem_reconfigure (shmem.c:?) 
[ 0.561390][ T0] get_tree_nodev (??:?) 
[ 0.562390][ T0] shmem_get_tree (shmem.c:?) 
[ 0.563390][ T0] vfs_get_tree (??:?) 
[ 0.563914][ T0] vfs_kern_mount (??:?) 
[ 0.564390][ T0] kern_mount (??:?) 
[ 0.564908][ T0] shmem_init (??:?) 
[ 0.565389][ T0] mnt_init (??:?) 
[ 0.565892][ T0] vfs_caches_init (??:?) 
[ 0.566390][ T0] start_kernel (??:?) 
[ 0.567390][ T0] i386_start_kernel (??:?) 
[ 0.568009][ T0] startup_32_smp (??:?) 
[    0.568392][    T0] irq event stamp: 1613
[ 0.568888][ T0] hardirqs last enabled at (1613): _raw_spin_unlock_irqrestore (??:?) 
[ 0.569389][ T0] hardirqs last disabled at (1612): _raw_spin_lock_irqsave (??:?) 
[ 0.570389][ T0] softirqs last enabled at (1480): do_softirq_own_stack (??:?) 
[ 0.571389][ T0] softirqs last disabled at (1473): do_softirq_own_stack (??:?) 
[    0.572389][    T0] ---[ end trace 0000000000000000 ]---
[    0.573889][    T0] Last level iTLB entries: 4KB 0, 2MB 0, 4MB 0
[    0.574391][    T0] Last level dTLB entries: 4KB 0, 2MB 0, 4MB 0, 1GB 0


To reproduce:

        # build kernel
	cd linux
	cp config-6.4.0-rc5-00004-g107ed33204f7 .config
	make HOSTCC=clang-15 CC=clang-15 ARCH=i386 olddefconfig prepare modules_prepare bzImage modules
	make HOSTCC=clang-15 CC=clang-15 ARCH=i386 INSTALL_MOD_PATH=<mod-install-dir> modules_install
	cd <mod-install-dir>
	find lib/ | cpio -o -H newc --quiet | gzip > modules.cgz


        git clone https://github.com/intel/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> -m modules.cgz job-script # job-script is attached in this email

        # if come across any failure that blocks the test,
        # please remove ~/.lkp and /lkp dir to run from a clean state.
Yujie Liu June 7, 2023, 7:33 a.m. UTC | #2 
On Wed, Jun 07, 2023 at 12:49:55PM +0800, kernel test robot wrote:
> 
> Hello,
> 
> kernel test robot noticed "INFO:trying_to_register_non-static_key" on:
> 
> commit: 107ed33204f77282d67b90f5c37f34c4b1ec9ffb ("[PATCH v2 2/3] mm: Split unregister_shrinker() in fast and slow part")
> url: https://github.com/intel-lab-lkp/linux/commits/Kirill-Tkhai/mm-vmscan-move-shrinker_debugfs_remove-before-synchronize_srcu/20230606-030419
> base: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git f8dba31b0a826e691949cd4fdfa5c30defaac8c5
> patch link: https://lore.kernel.org/all/168599179360.70911.4102140966715923751.stgit@pro.pro/
> patch subject: [PATCH v2 2/3] mm: Split unregister_shrinker() in fast and slow part
> 
> in testcase: boot
> 
> compiler: clang-15
> test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 4G
> 
> (please refer to attached dmesg/kmsg for entire log/backtrace)
> 
> 
> 
> If you fix the issue, kindly add following tag
> | Reported-by: kernel test robot <oliver.sang@intel.com>
> | Closes: https://lore.kernel.org/oe-lkp/202306071000.4ad4e5ba-oliver.sang@intel.com

Sorry the stacktrace in the report was broken due to a toolchain issue
in the bot. Please check the correct stacktrace as below:

[ 0.538549][ T0] INFO: trying to register non-static key.
[ 0.539249][ T0] The code is fine but needs lockdep annotation, or maybe
[ 0.539385][ T0] you didn't initialize this object before use?
[ 0.539385][ T0] turning off the locking correctness validator.
[ 0.539385][ T0] CPU: 0 PID: 0 Comm: swapper Not tainted 6.4.0-rc5-00004-g107ed33204f7 #1
[ 0.539385][ T0] Call Trace:
[ 0.539385][ T0] dump_stack_lvl (lib/dump_stack.c:?)
[ 0.539385][ T0] dump_stack (lib/dump_stack.c:113)
[ 0.539385][ T0] assign_lock_key (kernel/locking/lockdep.c:?)
[ 0.539385][ T0] register_lock_class (kernel/locking/lockdep.c:?)
[ 0.539385][ T0] __lock_acquire (kernel/locking/lockdep.c:4965)
[ 0.539385][ T0] ? lock_acquire (kernel/locking/lockdep.c:5705)
[ 0.539385][ T0] ? register_shrinker_prepared (mm/vmscan.c:760)
[ 0.539385][ T0] ? __might_resched (kernel/sched/core.c:10115)
[ 0.539385][ T0] lock_acquire (kernel/locking/lockdep.c:5705)
[ 0.539385][ T0] ? register_shrinker_prepared (mm/vmscan.c:762)
[ 0.539385][ T0] ? __might_resched (kernel/sched/core.c:10115)
[ 0.539385][ T0] down_write (kernel/locking/rwsem.c:1573)
[ 0.539385][ T0] ? register_shrinker_prepared (mm/vmscan.c:762)
[ 0.539385][ T0] register_shrinker_prepared (mm/vmscan.c:762)
[ 0.539385][ T0] sget_fc (fs/super.c:616)
[ 0.539385][ T0] ? kill_litter_super (fs/super.c:1121)
[ 0.539385][ T0] ? shmem_reconfigure (mm/shmem.c:3791)
[ 0.539385][ T0] get_tree_nodev (fs/super.c:1144)
[ 0.539385][ T0] shmem_get_tree (mm/shmem.c:3879)
[ 0.539385][ T0] vfs_get_tree (fs/super.c:1511)
[ 0.539385][ T0] vfs_kern_mount (fs/namespace.c:1036 fs/namespace.c:1065)
[ 0.539385][ T0] kern_mount (fs/namespace.c:4455)
[ 0.539385][ T0] shmem_init (mm/shmem.c:4106)
[ 0.539385][ T0] mnt_init (fs/namespace.c:4440)
[ 0.539385][ T0] vfs_caches_init (fs/dcache.c:3355)
[ 0.539385][ T0] start_kernel (init/main.c:1071)
[ 0.539385][ T0] i386_start_kernel (arch/x86/kernel/head32.c:56)
[ 0.539385][ T0] startup_32_smp (arch/x86/kernel/head_32.S:319)
[ 0.539391][ T0] ------------[ cut here ]------------
[ 0.540097][ T0] DEBUG_RWSEMS_WARN_ON(sem->magic != sem): count = 0x1, magic = 0x0, owner = 0x81d77c00, curr 0x81d77c00, list not empty
[ 0.540405][ T0] WARNING: CPU: 0 PID: 0 at kernel/locking/rwsem.c:1364 up_write (kernel/locking/rwsem.c:1364)
[ 0.541389][ T0] Modules linked in:
[ 0.542390][ T0] CPU: 0 PID: 0 Comm: swapper Not tainted 6.4.0-rc5-00004-g107ed33204f7 #1
[ 0.543389][ T0] EIP: up_write (kernel/locking/rwsem.c:1364)
[ 0.543920][ T0] Code: ee 8f c6 81 39 c1 74 05 bb 7f 8b c4 81 53 52 ff 74 24 08 57 ff 74 24 14 68 44 a3 cb 81 68 6d 1a ce 81 e8 32 68 fb ff 83 c4 1c <0f> 0b 39 f7 0f 85 a8 fe ff ff e9 a8 fe ff ff 0f 0b e9 db fe ff ff
All code
========
 0:     ee      out %al,(%dx)
 1:     8f c6   pop %rsi
 3:     81 39 c1 74 05 bb       cmpl $0xbb0574c1,(%rcx)
 9:     7f 8b   jg 0xffffffffffffff96
 b:     c4 81 53 52     (bad)
 f:     ff 74 24 08     push 0x8(%rsp)
 13:    57      push %rdi
 14:    ff 74 24 14     push 0x14(%rsp)
 18:    68 44 a3 cb 81  push $0xffffffff81cba344
 1d:    68 6d 1a ce 81  push $0xffffffff81ce1a6d
 22:    e8 32 68 fb ff  call 0xfffffffffffb6859
 27:    83 c4 1c        add $0x1c,%esp
 2a:*   0f 0b   ud2             <-- trapping instruction
 2c:    39 f7   cmp %esi,%edi
 2e:    0f 85 a8 fe ff ff       jne 0xfffffffffffffedc
 34:    e9 a8 fe ff ff  jmp 0xfffffffffffffee1
 39:    0f 0b   ud2
 3b:    e9 db fe ff ff  jmp 0xffffffffffffff1b

Code starting with the faulting instruction
===========================================
 0:     0f 0b   ud2
 2:     39 f7   cmp %esi,%edi
 4:     0f 85 a8 fe ff ff       jne 0xfffffffffffffeb2
 a:     e9 a8 fe ff ff  jmp 0xfffffffffffffeb7
 f:     0f 0b   ud2
 11:    e9 db fe ff ff  jmp 0xfffffffffffffef1
[ 0.544391][ T0] EAX: e6de3575 EBX: 81c48b7f ECX: e6de3575 EDX: 81d67dd0
[ 0.545388][ T0] ESI: 831f4c4c EDI: 00000000 EBP: 81d67ed0 ESP: 81d67ea8
[ 0.546389][ T0] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 00210292
[ 0.547388][ T0] CR0: 80050033 CR2: ffd98000 CR3: 02280000 CR4: 00040690
[ 0.548392][ T0] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
[ 0.549388][ T0] DR6: fffe0ff0 DR7: 00000400
[ 0.549947][ T0] Call Trace:
[ 0.550391][ T0] ? show_regs (arch/x86/kernel/dumpstack.c:478)
[ 0.550910][ T0] ? up_write (kernel/locking/rwsem.c:1364)
[ 0.551389][ T0] ? __warn (kernel/panic.c:235 kernel/panic.c:673)
[ 0.551869][ T0] ? up_write (kernel/locking/rwsem.c:1364)
[ 0.552389][ T0] ? up_write (kernel/locking/rwsem.c:1364)
[ 0.552921][ T0] ? report_bug (lib/bug.c:199)
[ 0.553390][ T0] ? exc_overflow (arch/x86/kernel/traps.c:337)
[ 0.554390][ T0] ? handle_bug (arch/x86/kernel/traps.c:324)
[ 0.554923][ T0] ? exc_invalid_op (arch/x86/kernel/traps.c:345)
[ 0.555390][ T0] ? handle_exception (arch/x86/entry/entry_32.S:1076)
[ 0.556022][ T0] ? arch_report_meminfo (arch/x86/mm/pat/set_memory.c:112)
[ 0.556389][ T0] ? exc_overflow (arch/x86/kernel/traps.c:337)
[ 0.557389][ T0] ? up_write (kernel/locking/rwsem.c:1364)
[ 0.557927][ T0] ? exc_overflow (arch/x86/kernel/traps.c:337)
[ 0.558389][ T0] ? up_write (kernel/locking/rwsem.c:1364)
[ 0.558904][ T0] register_shrinker_prepared (mm/vmscan.c:765)
[ 0.559390][ T0] sget_fc (fs/super.c:616)
[ 0.559887][ T0] ? kill_litter_super (fs/super.c:1121)
[ 0.560390][ T0] ? shmem_reconfigure (mm/shmem.c:3791)
[ 0.561390][ T0] get_tree_nodev (fs/super.c:1144)
[ 0.562390][ T0] shmem_get_tree (mm/shmem.c:3879)
[ 0.563390][ T0] vfs_get_tree (fs/super.c:1511)
[ 0.563914][ T0] vfs_kern_mount (fs/namespace.c:1036 fs/namespace.c:1065)
[ 0.564390][ T0] kern_mount (fs/namespace.c:4455)
[ 0.564908][ T0] shmem_init (mm/shmem.c:4106)
[ 0.565389][ T0] mnt_init (fs/namespace.c:4440)
[ 0.565892][ T0] vfs_caches_init (fs/dcache.c:3355)
[ 0.566390][ T0] start_kernel (init/main.c:1071)
[ 0.567390][ T0] i386_start_kernel (arch/x86/kernel/head32.c:56)
[ 0.568009][ T0] startup_32_smp (arch/x86/kernel/head_32.S:319)
[ 0.568392][ T0] irq event stamp: 1613
[ 0.568888][ T0] hardirqs last enabled at (1613): _raw_spin_unlock_irqrestore (arch/x86/include/asm/irqflags.h:42 arch/x86/include/asm/irqflags.h:77 arch/x86/include/asm/irqflags.h:135 include/linux/spinlock_api_smp.h:151 kernel/locking/spinlock.c:194)
[ 0.569389][ T0] hardirqs last disabled at (1612): _raw_spin_lock_irqsave (arch/x86/include/asm/preempt.h:80 include/linux/spinlock_api_smp.h:109 kernel/locking/spinlock.c:162)
[ 0.570389][ T0] softirqs last enabled at (1480): do_softirq_own_stack (arch/x86/kernel/irq_32.c:57 arch/x86/kernel/irq_32.c:147)
[ 0.571389][ T0] softirqs last disabled at (1473): do_softirq_own_stack (arch/x86/kernel/irq_32.c:57 arch/x86/kernel/irq_32.c:147)
[ 0.572389][ T0] ---[ end trace 0000000000000000 ]---
diff mbox series

Patch

diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
index 224293b2dd06..1cc572fa6070 100644
--- a/include/linux/shrinker.h
+++ b/include/linux/shrinker.h
@@ -4,6 +4,7 @@ 
 
 #include <linux/atomic.h>
 #include <linux/types.h>
+#include <linux/rwsem.h>
 
 /*
  * This struct is used to pass information from page reclaim to the shrinkers.
@@ -83,6 +84,7 @@  struct shrinker {
 #endif
 	/* objs pending delete, per node */
 	atomic_long_t *nr_deferred;
+	struct rw_semaphore rwsem;
 };
 #define DEFAULT_SEEKS 2 /* A good number if you don't know better. */
 
@@ -102,6 +104,8 @@  extern void register_shrinker_prepared(struct shrinker *shrinker);
 extern int __printf(2, 3) register_shrinker(struct shrinker *shrinker,
 					    const char *fmt, ...);
 extern void unregister_shrinker(struct shrinker *shrinker);
+extern void unregister_shrinker_delayed_initiate(struct shrinker *shrinker);
+extern void unregister_shrinker_delayed_finalize(struct shrinker *shrinker);
 extern void free_prealloced_shrinker(struct shrinker *shrinker);
 extern void synchronize_shrinkers(void);
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
index a773e97e152e..f24fd58dcc2a 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -706,6 +706,7 @@  static int __prealloc_shrinker(struct shrinker *shrinker)
 	if (!shrinker->nr_deferred)
 		return -ENOMEM;
 
+	init_rwsem(&shrinker->rwsem);
 	return 0;
 }
 
@@ -757,7 +758,9 @@  void register_shrinker_prepared(struct shrinker *shrinker)
 {
 	mutex_lock(&shrinker_mutex);
 	list_add_tail_rcu(&shrinker->list, &shrinker_list);
+	down_write(&shrinker->rwsem);
 	shrinker->flags |= SHRINKER_REGISTERED;
+	up_write(&shrinker->rwsem);
 	shrinker_debugfs_add(shrinker);
 	mutex_unlock(&shrinker_mutex);
 }
@@ -802,7 +805,7 @@  EXPORT_SYMBOL(register_shrinker);
 /*
  * Remove one
  */
-void unregister_shrinker(struct shrinker *shrinker)
+void unregister_shrinker_delayed_initiate(struct shrinker *shrinker)
 {
 	struct dentry *debugfs_entry;
 	int debugfs_id;
@@ -812,20 +815,33 @@  void unregister_shrinker(struct shrinker *shrinker)
 
 	mutex_lock(&shrinker_mutex);
 	list_del_rcu(&shrinker->list);
+	down_write(&shrinker->rwsem);
 	shrinker->flags &= ~SHRINKER_REGISTERED;
+	up_write(&shrinker->rwsem);
 	if (shrinker->flags & SHRINKER_MEMCG_AWARE)
 		unregister_memcg_shrinker(shrinker);
 	debugfs_entry = shrinker_debugfs_detach(shrinker, &debugfs_id);
 	mutex_unlock(&shrinker_mutex);
 
 	shrinker_debugfs_remove(debugfs_entry, debugfs_id);
+}
+EXPORT_SYMBOL(unregister_shrinker_delayed_initiate);
 
+void unregister_shrinker_delayed_finalize(struct shrinker *shrinker)
+{
 	atomic_inc(&shrinker_srcu_generation);
 	synchronize_srcu(&shrinker_srcu);
 
 	kfree(shrinker->nr_deferred);
 	shrinker->nr_deferred = NULL;
 }
+EXPORT_SYMBOL(unregister_shrinker_delayed_finalize);
+
+void unregister_shrinker(struct shrinker *shrinker)
+{
+	unregister_shrinker_delayed_initiate(shrinker);
+	unregister_shrinker_delayed_finalize(shrinker);
+}
 EXPORT_SYMBOL(unregister_shrinker);
 
 /**
@@ -856,9 +872,15 @@  static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
 					  : SHRINK_BATCH;
 	long scanned = 0, next_deferred;
 
+	if (!down_read_trylock(&shrinker->rwsem))
+		return 0;
+	if (!(shrinker->flags & SHRINKER_REGISTERED))
+		goto unlock;
 	freeable = shrinker->count_objects(shrinker, shrinkctl);
-	if (freeable == 0 || freeable == SHRINK_EMPTY)
-		return freeable;
+	if (freeable == 0 || freeable == SHRINK_EMPTY) {
+		freed = freeable;
+		goto unlock;
+	}
 
 	/*
 	 * copy the current shrinker scan count into a local variable
@@ -937,6 +959,8 @@  static unsigned long do_shrink_slab(struct shrink_control *shrinkctl,
 	new_nr = add_nr_deferred(next_deferred, shrinker, shrinkctl);
 
 	trace_mm_shrink_slab_end(shrinker, shrinkctl->nid, freed, nr, new_nr, total_scan);
+unlock:
+	up_read(&shrinker->rwsem);
 	return freed;
 }
 
@@ -968,9 +992,8 @@  static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid,
 		struct shrinker *shrinker;
 
 		shrinker = idr_find(&shrinker_idr, i);
-		if (unlikely(!shrinker || !(shrinker->flags & SHRINKER_REGISTERED))) {
-			if (!shrinker)
-				clear_bit(i, info->map);
+		if (unlikely(!shrinker)) {
+			clear_bit(i, info->map);
 			continue;
 		}