On Fri, Aug 23, 2019 at 1:35 AM Eric Biggers ebiggers@kernel.org wrote:
From: Eric Biggers ebiggers@google.com
When IOCB_CMD_POLL is used on the FUSE device, aio_poll() disables IRQs and takes kioctx::ctx_lock, then fuse_iqueue::waitq.lock.
Not in -linus.
Which tree was this reproduced with?
Thanks, Miklos
On Tue, Sep 03, 2019 at 09:31:29AM +0200, Miklos Szeredi wrote:
On Fri, Aug 23, 2019 at 1:35 AM Eric Biggers ebiggers@kernel.org wrote:
From: Eric Biggers ebiggers@google.com
When IOCB_CMD_POLL is used on the FUSE device, aio_poll() disables IRQs and takes kioctx::ctx_lock, then fuse_iqueue::waitq.lock.
Not in -linus.
Which tree was this reproduced with?
Thanks, Miklos
Linus's tree. Here's the full symbolized output on v5.3-rc7:
===================================================== WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected 5.3.0-rc7 #1 Not tainted ----------------------------------------------------- syz_fuse/150 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: 00000000c2701b26 (&fiq->waitq){+.+.}, at: spin_lock include/linux/spinlock.h:338 [inline] 00000000c2701b26 (&fiq->waitq){+.+.}, at: aio_poll fs/aio.c:1751 [inline] 00000000c2701b26 (&fiq->waitq){+.+.}, at: __io_submit_one.constprop.0+0x203/0x5b0 fs/aio.c:1825
and this task is already holding: 00000000f4c02e81 (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq include/linux/spinlock.h:363 [inline] 00000000f4c02e81 (&(&ctx->ctx_lock)->rlock){..-.}, at: aio_poll fs/aio.c:1749 [inline] 00000000f4c02e81 (&(&ctx->ctx_lock)->rlock){..-.}, at: __io_submit_one.constprop.0+0x1f4/0x5b0 fs/aio.c:1825 which would create a new lock dependency: (&(&ctx->ctx_lock)->rlock){..-.} -> (&fiq->waitq){+.+.}
but this new dependency connects a SOFTIRQ-irq-safe lock: (&(&ctx->ctx_lock)->rlock){..-.}
... which became SOFTIRQ-irq-safe at: lock_acquire+0x99/0x180 kernel/locking/lockdep.c:4412 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline] _raw_spin_lock_irq+0x32/0x50 kernel/locking/spinlock.c:167 spin_lock_irq include/linux/spinlock.h:363 [inline] free_ioctx_users+0x25/0x190 fs/aio.c:618 percpu_ref_put_many include/linux/percpu-refcount.h:293 [inline] percpu_ref_put include/linux/percpu-refcount.h:309 [inline] percpu_ref_call_confirm_rcu lib/percpu-refcount.c:130 [inline] percpu_ref_switch_to_atomic_rcu+0x202/0x210 lib/percpu-refcount.c:165 __rcu_reclaim kernel/rcu/rcu.h:222 [inline] rcu_do_batch+0x2ae/0x890 kernel/rcu/tree.c:2114 rcu_core+0x13a/0x370 kernel/rcu/tree.c:2314 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2323 __do_softirq+0xbe/0x400 kernel/softirq.c:292 invoke_softirq kernel/softirq.c:373 [inline] irq_exit+0x8f/0xc0 kernel/softirq.c:413 exiting_irq arch/x86/include/asm/apic.h:537 [inline] smp_apic_timer_interrupt+0x8e/0x210 arch/x86/kernel/apic/apic.c:1133 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830 native_safe_halt arch/x86/include/asm/irqflags.h:60 [inline] arch_safe_halt arch/x86/include/asm/irqflags.h:103 [inline] default_idle+0x29/0x160 arch/x86/kernel/process.c:580 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:571 default_idle_call+0x1e/0x30 kernel/sched/idle.c:94 cpuidle_idle_call kernel/sched/idle.c:154 [inline] do_idle+0x1f0/0x220 kernel/sched/idle.c:263 cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:354 rest_init+0x18a/0x24d init/main.c:451 arch_call_rest_init+0x9/0xc start_kernel+0x530/0x54e init/main.c:785 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:472 x86_64_start_kernel+0x6d/0x71 arch/x86/kernel/head64.c:453 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241
to a SOFTIRQ-irq-unsafe lock: (&fiq->waitq){+.+.}
... which became SOFTIRQ-irq-unsafe at: ... lock_acquire+0x99/0x180 kernel/locking/lockdep.c:4412 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2b/0x40 kernel/locking/spinlock.c:151 spin_lock include/linux/spinlock.h:338 [inline] flush_bg_queue+0x91/0xf0 fs/fuse/dev.c:415 fuse_request_queue_background+0xd1/0x140 fs/fuse/dev.c:676 fuse_request_send_background+0x27/0x60 fs/fuse/dev.c:687 fuse_send_init fs/fuse/inode.c:986 [inline] fuse_fill_super+0x656/0x681 fs/fuse/inode.c:1211 mount_nodev+0x42/0x90 fs/super.c:1329 fuse_mount+0x13/0x20 fs/fuse/inode.c:1236 legacy_get_tree+0x2c/0x50 fs/fs_context.c:661 vfs_get_tree+0x22/0xc0 fs/super.c:1413 do_new_mount fs/namespace.c:2791 [inline] do_mount+0x7e3/0xa60 fs/namespace.c:3111 ksys_mount+0x7d/0xd0 fs/namespace.c:3320 __do_sys_mount fs/namespace.c:3334 [inline] __se_sys_mount fs/namespace.c:3331 [inline] __x64_sys_mount+0x20/0x30 fs/namespace.c:3331 do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe
other info that might help us debug this:
Possible interrupt unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(&fiq->waitq); local_irq_disable(); lock(&(&ctx->ctx_lock)->rlock); lock(&fiq->waitq); <Interrupt> lock(&(&ctx->ctx_lock)->rlock);
*** DEADLOCK ***
1 lock held by syz_fuse/150: #0: 00000000f4c02e81 (&(&ctx->ctx_lock)->rlock){..-.}, at: spin_lock_irq include/linux/spinlock.h:363 [inline] #0: 00000000f4c02e81 (&(&ctx->ctx_lock)->rlock){..-.}, at: aio_poll fs/aio.c:1749 [inline] #0: 00000000f4c02e81 (&(&ctx->ctx_lock)->rlock){..-.}, at: __io_submit_one.constprop.0+0x1f4/0x5b0 fs/aio.c:1825
the dependencies between SOFTIRQ-irq-safe lock and the holding lock: -> (&(&ctx->ctx_lock)->rlock){..-.} { IN-SOFTIRQ-W at: lock_acquire+0x99/0x180 kernel/locking/lockdep.c:4412 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline] _raw_spin_lock_irq+0x32/0x50 kernel/locking/spinlock.c:167 spin_lock_irq include/linux/spinlock.h:363 [inline] free_ioctx_users+0x25/0x190 fs/aio.c:618 percpu_ref_put_many include/linux/percpu-refcount.h:293 [inline] percpu_ref_put include/linux/percpu-refcount.h:309 [inline] percpu_ref_call_confirm_rcu lib/percpu-refcount.c:130 [inline] percpu_ref_switch_to_atomic_rcu+0x202/0x210 lib/percpu-refcount.c:165 __rcu_reclaim kernel/rcu/rcu.h:222 [inline] rcu_do_batch+0x2ae/0x890 kernel/rcu/tree.c:2114 rcu_core+0x13a/0x370 kernel/rcu/tree.c:2314 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2323 __do_softirq+0xbe/0x400 kernel/softirq.c:292 invoke_softirq kernel/softirq.c:373 [inline] irq_exit+0x8f/0xc0 kernel/softirq.c:413 exiting_irq arch/x86/include/asm/apic.h:537 [inline] smp_apic_timer_interrupt+0x8e/0x210 arch/x86/kernel/apic/apic.c:1133 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830 native_safe_halt arch/x86/include/asm/irqflags.h:60 [inline] arch_safe_halt arch/x86/include/asm/irqflags.h:103 [inline] default_idle+0x29/0x160 arch/x86/kernel/process.c:580 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:571 default_idle_call+0x1e/0x30 kernel/sched/idle.c:94 cpuidle_idle_call kernel/sched/idle.c:154 [inline] do_idle+0x1f0/0x220 kernel/sched/idle.c:263 cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:354 rest_init+0x18a/0x24d init/main.c:451 arch_call_rest_init+0x9/0xc start_kernel+0x530/0x54e init/main.c:785 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:472 x86_64_start_kernel+0x6d/0x71 arch/x86/kernel/head64.c:453 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241 INITIAL USE at: lock_acquire+0x99/0x180 kernel/locking/lockdep.c:4412 __raw_spin_lock_irq include/linux/spinlock_api_smp.h:128 [inline] _raw_spin_lock_irq+0x32/0x50 kernel/locking/spinlock.c:167 spin_lock_irq include/linux/spinlock.h:363 [inline] free_ioctx_users+0x25/0x190 fs/aio.c:618 percpu_ref_put_many include/linux/percpu-refcount.h:293 [inline] percpu_ref_put include/linux/percpu-refcount.h:309 [inline] percpu_ref_call_confirm_rcu lib/percpu-refcount.c:130 [inline] percpu_ref_switch_to_atomic_rcu+0x202/0x210 lib/percpu-refcount.c:165 __rcu_reclaim kernel/rcu/rcu.h:222 [inline] rcu_do_batch+0x2ae/0x890 kernel/rcu/tree.c:2114 rcu_core+0x13a/0x370 kernel/rcu/tree.c:2314 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2323 __do_softirq+0xbe/0x400 kernel/softirq.c:292 invoke_softirq kernel/softirq.c:373 [inline] irq_exit+0x8f/0xc0 kernel/softirq.c:413 exiting_irq arch/x86/include/asm/apic.h:537 [inline] smp_apic_timer_interrupt+0x8e/0x210 arch/x86/kernel/apic/apic.c:1133 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830 native_safe_halt arch/x86/include/asm/irqflags.h:60 [inline] arch_safe_halt arch/x86/include/asm/irqflags.h:103 [inline] default_idle+0x29/0x160 arch/x86/kernel/process.c:580 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:571 default_idle_call+0x1e/0x30 kernel/sched/idle.c:94 cpuidle_idle_call kernel/sched/idle.c:154 [inline] do_idle+0x1f0/0x220 kernel/sched/idle.c:263 cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:354 rest_init+0x18a/0x24d init/main.c:451 arch_call_rest_init+0x9/0xc start_kernel+0x530/0x54e init/main.c:785 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:472 x86_64_start_kernel+0x6d/0x71 arch/x86/kernel/head64.c:453 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241 } ... key at: [<ffffffff82860670>] __key.50377+0x0/0x10 ... acquired at: check_prev_add+0xa7/0x950 kernel/locking/lockdep.c:2409 check_prevs_add kernel/locking/lockdep.c:2507 [inline] validate_chain+0x483/0x870 kernel/locking/lockdep.c:2897 __lock_acquire+0x447/0x7d0 kernel/locking/lockdep.c:3880 lock_acquire+0x99/0x180 kernel/locking/lockdep.c:4412 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2b/0x40 kernel/locking/spinlock.c:151 spin_lock include/linux/spinlock.h:338 [inline] aio_poll fs/aio.c:1751 [inline] __io_submit_one.constprop.0+0x203/0x5b0 fs/aio.c:1825 io_submit_one+0x146/0x5b0 fs/aio.c:1862 __do_sys_io_submit fs/aio.c:1921 [inline] __se_sys_io_submit+0x8e/0x270 fs/aio.c:1891 __x64_sys_io_submit+0x15/0x20 fs/aio.c:1891 do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe
the dependencies between the lock to be acquired and SOFTIRQ-irq-unsafe lock: -> (&fiq->waitq){+.+.} { HARDIRQ-ON-W at: lock_acquire+0x99/0x180 kernel/locking/lockdep.c:4412 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2b/0x40 kernel/locking/spinlock.c:151 spin_lock include/linux/spinlock.h:338 [inline] flush_bg_queue+0x91/0xf0 fs/fuse/dev.c:415 fuse_request_queue_background+0xd1/0x140 fs/fuse/dev.c:676 fuse_request_send_background+0x27/0x60 fs/fuse/dev.c:687 fuse_send_init fs/fuse/inode.c:986 [inline] fuse_fill_super+0x656/0x681 fs/fuse/inode.c:1211 mount_nodev+0x42/0x90 fs/super.c:1329 fuse_mount+0x13/0x20 fs/fuse/inode.c:1236 legacy_get_tree+0x2c/0x50 fs/fs_context.c:661 vfs_get_tree+0x22/0xc0 fs/super.c:1413 do_new_mount fs/namespace.c:2791 [inline] do_mount+0x7e3/0xa60 fs/namespace.c:3111 ksys_mount+0x7d/0xd0 fs/namespace.c:3320 __do_sys_mount fs/namespace.c:3334 [inline] __se_sys_mount fs/namespace.c:3331 [inline] __x64_sys_mount+0x20/0x30 fs/namespace.c:3331 do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe SOFTIRQ-ON-W at: lock_acquire+0x99/0x180 kernel/locking/lockdep.c:4412 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2b/0x40 kernel/locking/spinlock.c:151 spin_lock include/linux/spinlock.h:338 [inline] flush_bg_queue+0x91/0xf0 fs/fuse/dev.c:415 fuse_request_queue_background+0xd1/0x140 fs/fuse/dev.c:676 fuse_request_send_background+0x27/0x60 fs/fuse/dev.c:687 fuse_send_init fs/fuse/inode.c:986 [inline] fuse_fill_super+0x656/0x681 fs/fuse/inode.c:1211 mount_nodev+0x42/0x90 fs/super.c:1329 fuse_mount+0x13/0x20 fs/fuse/inode.c:1236 legacy_get_tree+0x2c/0x50 fs/fs_context.c:661 vfs_get_tree+0x22/0xc0 fs/super.c:1413 do_new_mount fs/namespace.c:2791 [inline] do_mount+0x7e3/0xa60 fs/namespace.c:3111 ksys_mount+0x7d/0xd0 fs/namespace.c:3320 __do_sys_mount fs/namespace.c:3334 [inline] __se_sys_mount fs/namespace.c:3331 [inline] __x64_sys_mount+0x20/0x30 fs/namespace.c:3331 do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe INITIAL USE at: lock_acquire+0x99/0x180 kernel/locking/lockdep.c:4412 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2b/0x40 kernel/locking/spinlock.c:151 spin_lock include/linux/spinlock.h:338 [inline] flush_bg_queue+0x91/0xf0 fs/fuse/dev.c:415 fuse_request_queue_background+0xd1/0x140 fs/fuse/dev.c:676 fuse_request_send_background+0x27/0x60 fs/fuse/dev.c:687 fuse_send_init fs/fuse/inode.c:986 [inline] fuse_fill_super+0x656/0x681 fs/fuse/inode.c:1211 mount_nodev+0x42/0x90 fs/super.c:1329 fuse_mount+0x13/0x20 fs/fuse/inode.c:1236 legacy_get_tree+0x2c/0x50 fs/fs_context.c:661 vfs_get_tree+0x22/0xc0 fs/super.c:1413 do_new_mount fs/namespace.c:2791 [inline] do_mount+0x7e3/0xa60 fs/namespace.c:3111 ksys_mount+0x7d/0xd0 fs/namespace.c:3320 __do_sys_mount fs/namespace.c:3334 [inline] __se_sys_mount fs/namespace.c:3331 [inline] __x64_sys_mount+0x20/0x30 fs/namespace.c:3331 do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe } ... key at: [<ffffffff82863ea0>] __key.40870+0x0/0x10 ... acquired at: check_prev_add+0xa7/0x950 kernel/locking/lockdep.c:2409 check_prevs_add kernel/locking/lockdep.c:2507 [inline] validate_chain+0x483/0x870 kernel/locking/lockdep.c:2897 __lock_acquire+0x447/0x7d0 kernel/locking/lockdep.c:3880 lock_acquire+0x99/0x180 kernel/locking/lockdep.c:4412 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2b/0x40 kernel/locking/spinlock.c:151 spin_lock include/linux/spinlock.h:338 [inline] aio_poll fs/aio.c:1751 [inline] __io_submit_one.constprop.0+0x203/0x5b0 fs/aio.c:1825 io_submit_one+0x146/0x5b0 fs/aio.c:1862 __do_sys_io_submit fs/aio.c:1921 [inline] __se_sys_io_submit+0x8e/0x270 fs/aio.c:1891 __x64_sys_io_submit+0x15/0x20 fs/aio.c:1891 do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe
stack backtrace: CPU: 1 PID: 150 Comm: syz_fuse Not tainted 5.3.0-rc7 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-20181126_142135-anatol 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x70/0x9a lib/dump_stack.c:113 print_bad_irq_dependency.cold+0x380/0x3d8 kernel/locking/lockdep.c:2025 check_irq_usage+0x337/0x400 kernel/locking/lockdep.c:2223 check_prev_add+0xa7/0x950 kernel/locking/lockdep.c:2409 check_prevs_add kernel/locking/lockdep.c:2507 [inline] validate_chain+0x483/0x870 kernel/locking/lockdep.c:2897 __lock_acquire+0x447/0x7d0 kernel/locking/lockdep.c:3880 lock_acquire+0x99/0x180 kernel/locking/lockdep.c:4412 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2b/0x40 kernel/locking/spinlock.c:151 spin_lock include/linux/spinlock.h:338 [inline] aio_poll fs/aio.c:1751 [inline] __io_submit_one.constprop.0+0x203/0x5b0 fs/aio.c:1825 io_submit_one+0x146/0x5b0 fs/aio.c:1862 __do_sys_io_submit fs/aio.c:1921 [inline] __se_sys_io_submit+0x8e/0x270 fs/aio.c:1891 __x64_sys_io_submit+0x15/0x20 fs/aio.c:1891 do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f1bbde7ec6d Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d f3 51 0c 00 f7 d8 64 89 01 48 RSP: 002b:00007ffffa3a70e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000d1 RAX: ffffffffffffffda RBX: 00007ffffa3a7140 RCX: 00007f1bbde7ec6d RDX: 00007ffffa3a70f8 RSI: 0000000000000001 RDI: 00007f1bbe27d000 RBP: 0000559337c29290 R08: 0000000000000000 R09: 00007f1bbe27d000 R10: 0000000000000029 R11: 0000000000000246 R12: 0000559337c29190 R13: 00007ffffa3a72b0 R14: 0000000000000000 R15: 0000000000000000
On Tue, Sep 3, 2019 at 3:39 PM Eric Biggers ebiggers@kernel.org wrote:
On Tue, Sep 03, 2019 at 09:31:29AM +0200, Miklos Szeredi wrote:
On Fri, Aug 23, 2019 at 1:35 AM Eric Biggers ebiggers@kernel.org wrote:
From: Eric Biggers ebiggers@google.com
When IOCB_CMD_POLL is used on the FUSE device, aio_poll() disables IRQs and takes kioctx::ctx_lock, then fuse_iqueue::waitq.lock.
Not in -linus.
Which tree was this reproduced with?
Thanks, Miklos
Linus's tree. Here's the full symbolized output on v5.3-rc7:
Okay.
TBH, I find the fix disgusting. It's confusing to sprinke code that has absolutely nothing to do with interrupts with spin_lock_irq() calls.
I think the lock/unlock calls should at least be done with a helper with a comment explaining why disabling interrupts is needed (though I have not managed to understand why aio needs to actually mess with the waitq lock...)
Probably a better fix would be to just use a separate spinlock to avoid the need to disable interrupts in cases where it's not necessary.
Thanks, Miklos
On Wed, Sep 04, 2019 at 04:29:03PM +0200, Miklos Szeredi wrote:
On Tue, Sep 3, 2019 at 3:39 PM Eric Biggers ebiggers@kernel.org wrote:
On Tue, Sep 03, 2019 at 09:31:29AM +0200, Miklos Szeredi wrote:
On Fri, Aug 23, 2019 at 1:35 AM Eric Biggers ebiggers@kernel.org wrote:
From: Eric Biggers ebiggers@google.com
When IOCB_CMD_POLL is used on the FUSE device, aio_poll() disables IRQs and takes kioctx::ctx_lock, then fuse_iqueue::waitq.lock.
Not in -linus.
Which tree was this reproduced with?
Thanks, Miklos
Linus's tree. Here's the full symbolized output on v5.3-rc7:
Okay.
TBH, I find the fix disgusting. It's confusing to sprinke code that has absolutely nothing to do with interrupts with spin_lock_irq() calls.
I think the lock/unlock calls should at least be done with a helper with a comment explaining why disabling interrupts is needed (though I have not managed to understand why aio needs to actually mess with the waitq lock...)
The aio code is doing a poll(), so it needs to use the wait queue.
Probably a better fix would be to just use a separate spinlock to avoid the need to disable interrupts in cases where it's not necessary.
Well, the below is what a separate lock would look like. Note that it actually still disables IRQs in some places; it's just hidden away in the nested spin_lock_irqsave() in wake_up(). Likewise, adding something to the fuse_iqueue then requires taking 2 spin locks -- one explicit, and one hidden in wake_up().
Is this the solution you'd prefer?
diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index ea8237513dfa..1d9d555f2699 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -377,7 +377,7 @@ static void queue_request(struct fuse_iqueue *fiq, struct fuse_req *req) req->in.h.len = sizeof(struct fuse_in_header) + len_args(req->in.numargs, (struct fuse_arg *) req->in.args); list_add_tail(&req->list, &fiq->pending); - wake_up_locked(&fiq->waitq); + wake_up(&fiq->waitq); kill_fasync(&fiq->fasync, SIGIO, POLL_IN); }
@@ -389,16 +389,16 @@ void fuse_queue_forget(struct fuse_conn *fc, struct fuse_forget_link *forget, forget->forget_one.nodeid = nodeid; forget->forget_one.nlookup = nlookup;
- spin_lock(&fiq->waitq.lock); + spin_lock(&fiq->lock); if (fiq->connected) { fiq->forget_list_tail->next = forget; fiq->forget_list_tail = forget; - wake_up_locked(&fiq->waitq); + wake_up(&fiq->waitq); kill_fasync(&fiq->fasync, SIGIO, POLL_IN); } else { kfree(forget); } - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock); }
static void flush_bg_queue(struct fuse_conn *fc) @@ -412,10 +412,10 @@ static void flush_bg_queue(struct fuse_conn *fc) req = list_first_entry(&fc->bg_queue, struct fuse_req, list); list_del(&req->list); fc->active_background++; - spin_lock(&fiq->waitq.lock); + spin_lock(&fiq->lock); req->in.h.unique = fuse_get_unique(fiq); queue_request(fiq, req); - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock); } }
@@ -439,9 +439,9 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req) * smp_mb() from queue_interrupt(). */ if (!list_empty(&req->intr_entry)) { - spin_lock(&fiq->waitq.lock); + spin_lock(&fiq->lock); list_del_init(&req->intr_entry); - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock); } WARN_ON(test_bit(FR_PENDING, &req->flags)); WARN_ON(test_bit(FR_SENT, &req->flags)); @@ -483,10 +483,10 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req)
static int queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req) { - spin_lock(&fiq->waitq.lock); + spin_lock(&fiq->lock); /* Check for we've sent request to interrupt this req */ if (unlikely(!test_bit(FR_INTERRUPTED, &req->flags))) { - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock); return -EINVAL; }
@@ -499,13 +499,13 @@ static int queue_interrupt(struct fuse_iqueue *fiq, struct fuse_req *req) smp_mb(); if (test_bit(FR_FINISHED, &req->flags)) { list_del_init(&req->intr_entry); - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock); return 0; } - wake_up_locked(&fiq->waitq); + wake_up(&fiq->waitq); kill_fasync(&fiq->fasync, SIGIO, POLL_IN); } - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock); return 0; }
@@ -535,16 +535,16 @@ static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req) if (!err) return;
- spin_lock(&fiq->waitq.lock); + spin_lock(&fiq->lock); /* Request is not yet in userspace, bail out */ if (test_bit(FR_PENDING, &req->flags)) { list_del(&req->list); - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock);; __fuse_put_request(req); req->out.h.error = -EINTR; return; } - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock); }
/* @@ -559,9 +559,9 @@ static void __fuse_request_send(struct fuse_conn *fc, struct fuse_req *req) struct fuse_iqueue *fiq = &fc->iq;
BUG_ON(test_bit(FR_BACKGROUND, &req->flags)); - spin_lock(&fiq->waitq.lock); + spin_lock_irq(&fiq->lock); if (!fiq->connected) { - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock); req->out.h.error = -ENOTCONN; } else { req->in.h.unique = fuse_get_unique(fiq); @@ -569,7 +569,7 @@ static void __fuse_request_send(struct fuse_conn *fc, struct fuse_req *req) /* acquire extra reference, since request is still needed after request_end() */ __fuse_get_request(req); - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock);
request_wait_answer(fc, req); /* Pairs with smp_wmb() in request_end() */ @@ -700,12 +700,12 @@ static int fuse_request_send_notify_reply(struct fuse_conn *fc,
__clear_bit(FR_ISREPLY, &req->flags); req->in.h.unique = unique; - spin_lock(&fiq->waitq.lock); + spin_lock(&fiq->lock); if (fiq->connected) { queue_request(fiq, req); err = 0; } - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock);
return err; } @@ -1149,12 +1149,12 @@ static int request_pending(struct fuse_iqueue *fiq) * Unlike other requests this is assembled on demand, without a need * to allocate a separate fuse_req structure. * - * Called with fiq->waitq.lock held, releases it + * Called with fiq->lock held, releases it */ static int fuse_read_interrupt(struct fuse_iqueue *fiq, struct fuse_copy_state *cs, size_t nbytes, struct fuse_req *req) -__releases(fiq->waitq.lock) +__releases(fiq->lock) { struct fuse_in_header ih; struct fuse_interrupt_in arg; @@ -1169,7 +1169,7 @@ __releases(fiq->waitq.lock) ih.unique = (req->in.h.unique | FUSE_INT_REQ_BIT); arg.unique = req->in.h.unique;
- spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock); if (nbytes < reqsize) return -EINVAL;
@@ -1206,7 +1206,7 @@ static struct fuse_forget_link *dequeue_forget(struct fuse_iqueue *fiq, static int fuse_read_single_forget(struct fuse_iqueue *fiq, struct fuse_copy_state *cs, size_t nbytes) -__releases(fiq->waitq.lock) +__releases(fiq->lock) { int err; struct fuse_forget_link *forget = dequeue_forget(fiq, 1, NULL); @@ -1220,7 +1220,7 @@ __releases(fiq->waitq.lock) .len = sizeof(ih) + sizeof(arg), };
- spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock); kfree(forget); if (nbytes < ih.len) return -EINVAL; @@ -1238,7 +1238,7 @@ __releases(fiq->waitq.lock)
static int fuse_read_batch_forget(struct fuse_iqueue *fiq, struct fuse_copy_state *cs, size_t nbytes) -__releases(fiq->waitq.lock) +__releases(fiq->lock) { int err; unsigned max_forgets; @@ -1252,13 +1252,13 @@ __releases(fiq->waitq.lock) };
if (nbytes < ih.len) { - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock); return -EINVAL; }
max_forgets = (nbytes - ih.len) / sizeof(struct fuse_forget_one); head = dequeue_forget(fiq, max_forgets, &count); - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock);
arg.count = count; ih.len += count * sizeof(struct fuse_forget_one); @@ -1288,7 +1288,7 @@ __releases(fiq->waitq.lock) static int fuse_read_forget(struct fuse_conn *fc, struct fuse_iqueue *fiq, struct fuse_copy_state *cs, size_t nbytes) -__releases(fiq->waitq.lock) +__releases(fiq->lock) { if (fc->minor < 16 || fiq->forget_list_head.next->next == NULL) return fuse_read_single_forget(fiq, cs, nbytes); @@ -1318,16 +1318,19 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file, unsigned int hash;
restart: - spin_lock(&fiq->waitq.lock); - err = -EAGAIN; - if ((file->f_flags & O_NONBLOCK) && fiq->connected && - !request_pending(fiq)) - goto err_unlock; + for (;;) { + spin_lock(&fiq->lock); + if (!fiq->connected || request_pending(fiq)) + break; + spin_unlock(&fiq->lock);
- err = wait_event_interruptible_exclusive_locked(fiq->waitq, + if (file->f_flags & O_NONBLOCK) + return -EAGAIN; + err = wait_event_interruptible_exclusive(fiq->waitq, !fiq->connected || request_pending(fiq)); - if (err) - goto err_unlock; + if (err) + return err; + }
if (!fiq->connected) { err = fc->aborted ? -ECONNABORTED : -ENODEV; @@ -1351,7 +1354,7 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file, req = list_entry(fiq->pending.next, struct fuse_req, list); clear_bit(FR_PENDING, &req->flags); list_del_init(&req->list); - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock);
in = &req->in; reqsize = in->h.len; @@ -1409,7 +1412,7 @@ static ssize_t fuse_dev_do_read(struct fuse_dev *fud, struct file *file, return err;
err_unlock: - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock); return err; }
@@ -2121,12 +2124,12 @@ static __poll_t fuse_dev_poll(struct file *file, poll_table *wait) fiq = &fud->fc->iq; poll_wait(file, &fiq->waitq, wait);
- spin_lock(&fiq->waitq.lock); + spin_lock(&fiq->lock); if (!fiq->connected) mask = EPOLLERR; else if (request_pending(fiq)) mask |= EPOLLIN | EPOLLRDNORM; - spin_unlock(&fiq->waitq.lock); + spin_unlock(&fiq->lock);
return mask; } @@ -2221,15 +2224,15 @@ void fuse_abort_conn(struct fuse_conn *fc) flush_bg_queue(fc); spin_unlock(&fc->bg_lock);
- spin_lock(&fiq->waitq.lock); + spin_lock(&fiq->lock); fiq->connected = 0; list_for_each_entry(req, &fiq->pending, list) clear_bit(FR_PENDING, &req->flags); list_splice_tail_init(&fiq->pending, &to_end); while (forget_pending(fiq)) kfree(dequeue_forget(fiq, 1, NULL)); - wake_up_all_locked(&fiq->waitq); - spin_unlock(&fiq->waitq.lock); + wake_up_all(&fiq->waitq); + spin_unlock(&fiq->lock); kill_fasync(&fiq->fasync, SIGIO, POLL_IN); end_polls(fc); wake_up_all(&fc->blocked_waitq); diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 24dbca777775..5de7fd0fd6ef 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -450,6 +450,9 @@ struct fuse_iqueue { /** Connection established */ unsigned connected;
+ /** Lock protecting accessess to members of this structure */ + spinlock_t lock; + /** Readers of the connection are waiting on this */ wait_queue_head_t waitq;
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index 4bb885b0f032..987877860c01 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -582,6 +582,7 @@ static int fuse_show_options(struct seq_file *m, struct dentry *root) static void fuse_iqueue_init(struct fuse_iqueue *fiq) { memset(fiq, 0, sizeof(struct fuse_iqueue)); + spin_lock_init(&fiq->lock); init_waitqueue_head(&fiq->waitq); INIT_LIST_HEAD(&fiq->pending); INIT_LIST_HEAD(&fiq->interrupts);
On Fri, Sep 6, 2019 at 6:43 AM Eric Biggers ebiggers@kernel.org wrote:
On Wed, Sep 04, 2019 at 04:29:03PM +0200, Miklos Szeredi wrote:
TBH, I find the fix disgusting. It's confusing to sprinke code that has absolutely nothing to do with interrupts with spin_lock_irq() calls.
I think the lock/unlock calls should at least be done with a helper with a comment explaining why disabling interrupts is needed (though I have not managed to understand why aio needs to actually mess with the waitq lock...)
The aio code is doing a poll(), so it needs to use the wait queue.
Doesn't explain why the irq disabled nested locking is needed in aio_poll(). poll/select manage to do that without messing with waitq internals. How is aio poll different?
Probably a better fix would be to just use a separate spinlock to avoid the need to disable interrupts in cases where it's not necessary.
Well, the below is what a separate lock would look like. Note that it actually still disables IRQs in some places; it's just hidden away in the nested spin_lock_irqsave() in wake_up(). Likewise, adding something to the fuse_iqueue then requires taking 2 spin locks -- one explicit, and one hidden in wake_up().
Right, that's exactly why the waitq lock was used.
Is this the solution you'd prefer?
I'd actually prefer if aio was fixed. But I guess that's not realistic, so yes, the below patch looks okay. If fiq->lock is in the same cacheline as fiq->waitq then it shouldn't make a difference.
Thanks, Miklos
linux-stable-mirror@lists.linaro.org
-
Eric Biggers -
Miklos Szeredi