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9 Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
Xu Kuohai
|
4b45cd81f7 |
bpf: Initialize same number of free nodes for each pcpu_freelist
pcpu_freelist_populate() initializes nr_elems / num_possible_cpus() + 1
free nodes for some CPUs, and then possibly one CPU with fewer nodes,
followed by remaining cpus with 0 nodes. For example, when nr_elems == 256
and num_possible_cpus() == 32, CPU 0~27 each gets 9 free nodes, CPU 28 gets
4 free nodes, CPU 29~31 get 0 free nodes, while in fact each CPU should get
8 nodes equally.
This patch initializes nr_elems / num_possible_cpus() free nodes for each
CPU firstly, then allocates the remaining free nodes by one for each CPU
until no free nodes left.
Fixes:
|
||
Punit Agrawal
|
57c92f11a2 |
bpf: Simplify code by using for_each_cpu_wrap()
In the percpu freelist code, it is a common pattern to iterate over the possible CPUs mask starting with the current CPU. The pattern is implemented using a hand rolled while loop with the loop variable increment being open-coded. Simplify the code by using for_each_cpu_wrap() helper to iterate over the possible cpus starting with the current CPU. As a result, some of the special-casing in the loop also gets simplified. No functional change intended. Signed-off-by: Punit Agrawal <punit.agrawal@bytedance.com> Acked-by: Song Liu <song@kernel.org> Link: https://lore.kernel.org/r/20220907155746.1750329-1-punit.agrawal@bytedance.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
||
Feng Zhou
|
54a9c3a42d |
bpf: avoid grabbing spin_locks of all cpus when no free elems
This patch use head->first in pcpu_freelist_head to check freelist
having free or not. If having, grab spin_lock, or check next cpu's
freelist.
Before patch: hash_map performance
./map_perf_test 1
0:hash_map_perf pre-alloc 1043397 events per sec
...
The average of the test results is around 1050000 events per sec.
hash_map the worst: no free
./run_bench_bpf_hashmap_full_update.sh
Setting up benchmark 'bpf-hashmap-ful-update'...
Benchmark 'bpf-hashmap-ful-update' started.
1:hash_map_full_perf 15687 events per sec
...
The average of the test results is around 16000 events per sec.
ftrace trace:
0) | htab_map_update_elem() {
0) | __pcpu_freelist_pop() {
0) | _raw_spin_lock()
0) | _raw_spin_unlock()
0) | ...
0) + 25.188 us | }
0) + 28.439 us | }
The test machine is 16C, trying to get spin_lock 17 times, in addition
to 16c, there is an extralist.
after patch: hash_map performance
./map_perf_test 1
0:hash_map_perf pre-alloc 1053298 events per sec
...
The average of the test results is around 1050000 events per sec.
hash_map worst: no free
./run_bench_bpf_hashmap_full_update.sh
Setting up benchmark 'bpf-hashmap-ful-update'...
Benchmark 'bpf-hashmap-ful-update' started.
1:hash_map_full_perf 555830 events per sec
...
The average of the test results is around 550000 events per sec.
ftrace trace:
0) | htab_map_update_elem() {
0) | alloc_htab_elem() {
0) 0.586 us | __pcpu_freelist_pop();
0) 0.945 us | }
0) 8.669 us | }
It can be seen that after adding this patch, the map performance is
almost not degraded, and when free=0, first check head->first instead of
directly acquiring spin_lock.
Co-developed-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com>
Link: https://lore.kernel.org/r/20220610023308.93798-2-zhoufeng.zf@bytedance.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
|
||
Song Liu
|
39d8f0d102 |
bpf: Use raw_spin_trylock() for pcpu_freelist_push/pop in NMI
Recent improvements in LOCKDEP highlighted a potential A-A deadlock with pcpu_freelist in NMI: ./tools/testing/selftests/bpf/test_progs -t stacktrace_build_id_nmi [ 18.984807] ================================ [ 18.984807] WARNING: inconsistent lock state [ 18.984808] 5.9.0-rc6-01771-g1466de1330e1 #2967 Not tainted [ 18.984809] -------------------------------- [ 18.984809] inconsistent {INITIAL USE} -> {IN-NMI} usage. [ 18.984810] test_progs/1990 [HC2[2]:SC0[0]:HE0:SE1] takes: [ 18.984810] ffffe8ffffc219c0 (&head->lock){....}-{2:2}, at: __pcpu_freelist_pop+0xe3/0x180 [ 18.984813] {INITIAL USE} state was registered at: [ 18.984814] lock_acquire+0x175/0x7c0 [ 18.984814] _raw_spin_lock+0x2c/0x40 [ 18.984815] __pcpu_freelist_pop+0xe3/0x180 [ 18.984815] pcpu_freelist_pop+0x31/0x40 [ 18.984816] htab_map_alloc+0xbbf/0xf40 [ 18.984816] __do_sys_bpf+0x5aa/0x3ed0 [ 18.984817] do_syscall_64+0x2d/0x40 [ 18.984818] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 18.984818] irq event stamp: 12 [...] [ 18.984822] other info that might help us debug this: [ 18.984823] Possible unsafe locking scenario: [ 18.984823] [ 18.984824] CPU0 [ 18.984824] ---- [ 18.984824] lock(&head->lock); [ 18.984826] <Interrupt> [ 18.984826] lock(&head->lock); [ 18.984827] [ 18.984828] *** DEADLOCK *** [ 18.984828] [ 18.984829] 2 locks held by test_progs/1990: [...] [ 18.984838] <NMI> [ 18.984838] dump_stack+0x9a/0xd0 [ 18.984839] lock_acquire+0x5c9/0x7c0 [ 18.984839] ? lock_release+0x6f0/0x6f0 [ 18.984840] ? __pcpu_freelist_pop+0xe3/0x180 [ 18.984840] _raw_spin_lock+0x2c/0x40 [ 18.984841] ? __pcpu_freelist_pop+0xe3/0x180 [ 18.984841] __pcpu_freelist_pop+0xe3/0x180 [ 18.984842] pcpu_freelist_pop+0x17/0x40 [ 18.984842] ? lock_release+0x6f0/0x6f0 [ 18.984843] __bpf_get_stackid+0x534/0xaf0 [ 18.984843] bpf_prog_1fd9e30e1438d3c5_oncpu+0x73/0x350 [ 18.984844] bpf_overflow_handler+0x12f/0x3f0 This is because pcpu_freelist_head.lock is accessed in both NMI and non-NMI context. Fix this issue by using raw_spin_trylock() in NMI. Since NMI interrupts non-NMI context, when NMI context tries to lock the raw_spinlock, non-NMI context of the same CPU may already have locked a lock and is blocked from unlocking the lock. For a system with N CPUs, there could be N NMIs at the same time, and they may block N non-NMI raw_spinlocks. This is tricky for pcpu_freelist_push(), where unlike _pop(), failing _push() means leaking memory. This issue is more likely to trigger in non-SMP system. Fix this issue with an extra list, pcpu_freelist.extralist. The extralist is primarily used to take _push() when raw_spin_trylock() failed on all the per CPU lists. It should be empty most of the time. The following table summarizes the behavior of pcpu_freelist in NMI and non-NMI: non-NMI pop(): use _lock(); check per CPU lists first; if all per CPU lists are empty, check extralist; if extralist is empty, return NULL. non-NMI push(): use _lock(); only push to per CPU lists. NMI pop(): use _trylock(); check per CPU lists first; if all per CPU lists are locked or empty, check extralist; if extralist is locked or empty, return NULL. NMI push(): use _trylock(); check per CPU lists first; if all per CPU lists are locked; try push to extralist; if extralist is also locked, keep trying on per CPU lists. Reported-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Song Liu <songliubraving@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20201005165838.3735218-1-songliubraving@fb.com |
||
Thomas Gleixner
|
569de905eb |
bpf: Dont iterate over possible CPUs with interrupts disabled
pcpu_freelist_populate() is disabling interrupts and then iterates over the possible CPUs. The reason why this disables interrupts is to silence lockdep because the invoked ___pcpu_freelist_push() takes spin locks. Neither the interrupt disabling nor the locking are required in this function because it's called during initialization and the resulting map is not yet visible to anything. Split out the actual push assignement into an inline, call it from the loop and remove the interrupt disable. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200224145643.365930116@linutronix.de |
||
|
Thomas Gleixner
|
25763b3c86 |
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 206
Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of version 2 of the gnu general public license as published by the free software foundation extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 107 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Allison Randal <allison@lohutok.net> Reviewed-by: Richard Fontana <rfontana@redhat.com> Reviewed-by: Steve Winslow <swinslow@gmail.com> Reviewed-by: Alexios Zavras <alexios.zavras@intel.com> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190528171438.615055994@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
||
Alexei Starovoitov
|
a89fac57b5 |
bpf: fix lockdep false positive in percpu_freelist
Lockdep warns about false positive:
[ 12.492084] 00000000e6b28347 (&head->lock){+...}, at: pcpu_freelist_push+0x2a/0x40
[ 12.492696] but this lock was taken by another, HARDIRQ-safe lock in the past:
[ 12.493275] (&rq->lock){-.-.}
[ 12.493276]
[ 12.493276]
[ 12.493276] and interrupts could create inverse lock ordering between them.
[ 12.493276]
[ 12.494435]
[ 12.494435] other info that might help us debug this:
[ 12.494979] Possible interrupt unsafe locking scenario:
[ 12.494979]
[ 12.495518] CPU0 CPU1
[ 12.495879] ---- ----
[ 12.496243] lock(&head->lock);
[ 12.496502] local_irq_disable();
[ 12.496969] lock(&rq->lock);
[ 12.497431] lock(&head->lock);
[ 12.497890] <Interrupt>
[ 12.498104] lock(&rq->lock);
[ 12.498368]
[ 12.498368] *** DEADLOCK ***
[ 12.498368]
[ 12.498837] 1 lock held by dd/276:
[ 12.499110] #0: 00000000c58cb2ee (rcu_read_lock){....}, at: trace_call_bpf+0x5e/0x240
[ 12.499747]
[ 12.499747] the shortest dependencies between 2nd lock and 1st lock:
[ 12.500389] -> (&rq->lock){-.-.} {
[ 12.500669] IN-HARDIRQ-W at:
[ 12.500934] _raw_spin_lock+0x2f/0x40
[ 12.501373] scheduler_tick+0x4c/0xf0
[ 12.501812] update_process_times+0x40/0x50
[ 12.502294] tick_periodic+0x27/0xb0
[ 12.502723] tick_handle_periodic+0x1f/0x60
[ 12.503203] timer_interrupt+0x11/0x20
[ 12.503651] __handle_irq_event_percpu+0x43/0x2c0
[ 12.504167] handle_irq_event_percpu+0x20/0x50
[ 12.504674] handle_irq_event+0x37/0x60
[ 12.505139] handle_level_irq+0xa7/0x120
[ 12.505601] handle_irq+0xa1/0x150
[ 12.506018] do_IRQ+0x77/0x140
[ 12.506411] ret_from_intr+0x0/0x1d
[ 12.506834] _raw_spin_unlock_irqrestore+0x53/0x60
[ 12.507362] __setup_irq+0x481/0x730
[ 12.507789] setup_irq+0x49/0x80
[ 12.508195] hpet_time_init+0x21/0x32
[ 12.508644] x86_late_time_init+0xb/0x16
[ 12.509106] start_kernel+0x390/0x42a
[ 12.509554] secondary_startup_64+0xa4/0xb0
[ 12.510034] IN-SOFTIRQ-W at:
[ 12.510305] _raw_spin_lock+0x2f/0x40
[ 12.510772] try_to_wake_up+0x1c7/0x4e0
[ 12.511220] swake_up_locked+0x20/0x40
[ 12.511657] swake_up_one+0x1a/0x30
[ 12.512070] rcu_process_callbacks+0xc5/0x650
[ 12.512553] __do_softirq+0xe6/0x47b
[ 12.512978] irq_exit+0xc3/0xd0
[ 12.513372] smp_apic_timer_interrupt+0xa9/0x250
[ 12.513876] apic_timer_interrupt+0xf/0x20
[ 12.514343] default_idle+0x1c/0x170
[ 12.514765] do_idle+0x199/0x240
[ 12.515159] cpu_startup_entry+0x19/0x20
[ 12.515614] start_kernel+0x422/0x42a
[ 12.516045] secondary_startup_64+0xa4/0xb0
[ 12.516521] INITIAL USE at:
[ 12.516774] _raw_spin_lock_irqsave+0x38/0x50
[ 12.517258] rq_attach_root+0x16/0xd0
[ 12.517685] sched_init+0x2f2/0x3eb
[ 12.518096] start_kernel+0x1fb/0x42a
[ 12.518525] secondary_startup_64+0xa4/0xb0
[ 12.518986] }
[ 12.519132] ... key at: [<ffffffff82b7bc28>] __key.71384+0x0/0x8
[ 12.519649] ... acquired at:
[ 12.519892] pcpu_freelist_pop+0x7b/0xd0
[ 12.520221] bpf_get_stackid+0x1d2/0x4d0
[ 12.520563] ___bpf_prog_run+0x8b4/0x11a0
[ 12.520887]
[ 12.521008] -> (&head->lock){+...} {
[ 12.521292] HARDIRQ-ON-W at:
[ 12.521539] _raw_spin_lock+0x2f/0x40
[ 12.521950] pcpu_freelist_push+0x2a/0x40
[ 12.522396] bpf_get_stackid+0x494/0x4d0
[ 12.522828] ___bpf_prog_run+0x8b4/0x11a0
[ 12.523296] INITIAL USE at:
[ 12.523537] _raw_spin_lock+0x2f/0x40
[ 12.523944] pcpu_freelist_populate+0xc0/0x120
[ 12.524417] htab_map_alloc+0x405/0x500
[ 12.524835] __do_sys_bpf+0x1a3/0x1a90
[ 12.525253] do_syscall_64+0x4a/0x180
[ 12.525659] entry_SYSCALL_64_after_hwframe+0x49/0xbe
[ 12.526167] }
[ 12.526311] ... key at: [<ffffffff838f7668>] __key.13130+0x0/0x8
[ 12.526812] ... acquired at:
[ 12.527047] __lock_acquire+0x521/0x1350
[ 12.527371] lock_acquire+0x98/0x190
[ 12.527680] _raw_spin_lock+0x2f/0x40
[ 12.527994] pcpu_freelist_push+0x2a/0x40
[ 12.528325] bpf_get_stackid+0x494/0x4d0
[ 12.528645] ___bpf_prog_run+0x8b4/0x11a0
[ 12.528970]
[ 12.529092]
[ 12.529092] stack backtrace:
[ 12.529444] CPU: 0 PID: 276 Comm: dd Not tainted 5.0.0-rc3-00018-g2fa53f892422 #475
[ 12.530043] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
[ 12.530750] Call Trace:
[ 12.530948] dump_stack+0x5f/0x8b
[ 12.531248] check_usage_backwards+0x10c/0x120
[ 12.531598] ? ___bpf_prog_run+0x8b4/0x11a0
[ 12.531935] ? mark_lock+0x382/0x560
[ 12.532229] mark_lock+0x382/0x560
[ 12.532496] ? print_shortest_lock_dependencies+0x180/0x180
[ 12.532928] __lock_acquire+0x521/0x1350
[ 12.533271] ? find_get_entry+0x17f/0x2e0
[ 12.533586] ? find_get_entry+0x19c/0x2e0
[ 12.533902] ? lock_acquire+0x98/0x190
[ 12.534196] lock_acquire+0x98/0x190
[ 12.534482] ? pcpu_freelist_push+0x2a/0x40
[ 12.534810] _raw_spin_lock+0x2f/0x40
[ 12.535099] ? pcpu_freelist_push+0x2a/0x40
[ 12.535432] pcpu_freelist_push+0x2a/0x40
[ 12.535750] bpf_get_stackid+0x494/0x4d0
[ 12.536062] ___bpf_prog_run+0x8b4/0x11a0
It has been explained that is a false positive here:
https://lkml.org/lkml/2018/7/25/756
Recap:
- stackmap uses pcpu_freelist
- The lock in pcpu_freelist is a percpu lock
- stackmap is only used by tracing bpf_prog
- A tracing bpf_prog cannot be run if another bpf_prog
has already been running (ensured by the percpu bpf_prog_active counter).
Eric pointed out that this lockdep splats stops other
legit lockdep splats in selftests/bpf/test_progs.c.
Fix this by calling local_irq_save/restore for stackmap.
Another false positive had also been worked around by calling
local_irq_save in commit
|
||
Eric Dumazet
|
89ad2fa3f0 |
bpf: fix lockdep splat
pcpu_freelist_pop() needs the same lockdep awareness than
pcpu_freelist_populate() to avoid a false positive.
[ INFO: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected ]
switchto-defaul/12508 [HC0[0]:SC0[6]:HE0:SE0] is trying to acquire:
(&htab->buckets[i].lock){......}, at: [<ffffffff9dc099cb>] __htab_percpu_map_update_elem+0x1cb/0x300
and this task is already holding:
(dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2){+.-...}, at: [<ffffffff9e135848>] __dev_queue_xmit+0
x868/0x1240
which would create a new lock dependency:
(dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2){+.-...} -> (&htab->buckets[i].lock){......}
but this new dependency connects a SOFTIRQ-irq-safe lock:
(dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2){+.-...}
... which became SOFTIRQ-irq-safe at:
[<ffffffff9db5931b>] __lock_acquire+0x42b/0x1f10
[<ffffffff9db5b32c>] lock_acquire+0xbc/0x1b0
[<ffffffff9da05e38>] _raw_spin_lock+0x38/0x50
[<ffffffff9e135848>] __dev_queue_xmit+0x868/0x1240
[<ffffffff9e136240>] dev_queue_xmit+0x10/0x20
[<ffffffff9e1965d9>] ip_finish_output2+0x439/0x590
[<ffffffff9e197410>] ip_finish_output+0x150/0x2f0
[<ffffffff9e19886d>] ip_output+0x7d/0x260
[<ffffffff9e19789e>] ip_local_out+0x5e/0xe0
[<ffffffff9e197b25>] ip_queue_xmit+0x205/0x620
[<ffffffff9e1b8398>] tcp_transmit_skb+0x5a8/0xcb0
[<ffffffff9e1ba152>] tcp_write_xmit+0x242/0x1070
[<ffffffff9e1baffc>] __tcp_push_pending_frames+0x3c/0xf0
[<ffffffff9e1b3472>] tcp_rcv_established+0x312/0x700
[<ffffffff9e1c1acc>] tcp_v4_do_rcv+0x11c/0x200
[<ffffffff9e1c3dc2>] tcp_v4_rcv+0xaa2/0xc30
[<ffffffff9e191107>] ip_local_deliver_finish+0xa7/0x240
[<ffffffff9e191a36>] ip_local_deliver+0x66/0x200
[<ffffffff9e19137d>] ip_rcv_finish+0xdd/0x560
[<ffffffff9e191e65>] ip_rcv+0x295/0x510
[<ffffffff9e12ff88>] __netif_receive_skb_core+0x988/0x1020
[<ffffffff9e130641>] __netif_receive_skb+0x21/0x70
[<ffffffff9e1306ff>] process_backlog+0x6f/0x230
[<ffffffff9e132129>] net_rx_action+0x229/0x420
[<ffffffff9da07ee8>] __do_softirq+0xd8/0x43d
[<ffffffff9e282bcc>] do_softirq_own_stack+0x1c/0x30
[<ffffffff9dafc2f5>] do_softirq+0x55/0x60
[<ffffffff9dafc3a8>] __local_bh_enable_ip+0xa8/0xb0
[<ffffffff9db4c727>] cpu_startup_entry+0x1c7/0x500
[<ffffffff9daab333>] start_secondary+0x113/0x140
to a SOFTIRQ-irq-unsafe lock:
(&head->lock){+.+...}
... which became SOFTIRQ-irq-unsafe at:
... [<ffffffff9db5971f>] __lock_acquire+0x82f/0x1f10
[<ffffffff9db5b32c>] lock_acquire+0xbc/0x1b0
[<ffffffff9da05e38>] _raw_spin_lock+0x38/0x50
[<ffffffff9dc0b7fa>] pcpu_freelist_pop+0x7a/0xb0
[<ffffffff9dc08b2c>] htab_map_alloc+0x50c/0x5f0
[<ffffffff9dc00dc5>] SyS_bpf+0x265/0x1200
[<ffffffff9e28195f>] entry_SYSCALL_64_fastpath+0x12/0x17
other info that might help us debug this:
Chain exists of:
dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2 --> &htab->buckets[i].lock --> &head->lock
Possible interrupt unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&head->lock);
local_irq_disable();
lock(dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2);
lock(&htab->buckets[i].lock);
<Interrupt>
lock(dev_queue->dev->qdisc_class ?: &qdisc_tx_lock#2);
*** DEADLOCK ***
Fixes:
|
||
Alexei Starovoitov
|
e19494edab |
bpf: introduce percpu_freelist
Introduce simple percpu_freelist to keep single list of elements spread across per-cpu singly linked lists. /* push element into the list */ void pcpu_freelist_push(struct pcpu_freelist *, struct pcpu_freelist_node *); /* pop element from the list */ struct pcpu_freelist_node *pcpu_freelist_pop(struct pcpu_freelist *); The object is pushed to the current cpu list. Pop first trying to get the object from the current cpu list, if it's empty goes to the neigbour cpu list. For bpf program usage pattern the collision rate is very low, since programs push and pop the objects typically on the same cpu. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net> |