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author | 2023-02-21 18:24:12 -0800 | |
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committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/translations/zh_CN/core-api/kref.rst | |
download | linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip |
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
Pull networking updates from Jakub Kicinski:
"Core:
- Add dedicated kmem_cache for typical/small skb->head, avoid having
to access struct page at kfree time, and improve memory use.
- Introduce sysctl to set default RPS configuration for new netdevs.
- Define Netlink protocol specification format which can be used to
describe messages used by each family and auto-generate parsers.
Add tools for generating kernel data structures and uAPI headers.
- Expose all net/core sysctls inside netns.
- Remove 4s sleep in netpoll if carrier is instantly detected on
boot.
- Add configurable limit of MDB entries per port, and port-vlan.
- Continue populating drop reasons throughout the stack.
- Retire a handful of legacy Qdiscs and classifiers.
Protocols:
- Support IPv4 big TCP (TSO frames larger than 64kB).
- Add IP_LOCAL_PORT_RANGE socket option, to control local port range
on socket by socket basis.
- Track and report in procfs number of MPTCP sockets used.
- Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
manager.
- IPv6: don't check net.ipv6.route.max_size and rely on garbage
collection to free memory (similarly to IPv4).
- Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).
- ICMP: add per-rate limit counters.
- Add support for user scanning requests in ieee802154.
- Remove static WEP support.
- Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
reporting.
- WiFi 7 EHT channel puncturing support (client & AP).
BPF:
- Add a rbtree data structure following the "next-gen data structure"
precedent set by recently added linked list, that is, by using
kfunc + kptr instead of adding a new BPF map type.
- Expose XDP hints via kfuncs with initial support for RX hash and
timestamp metadata.
- Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
better support decap on GRE tunnel devices not operating in collect
metadata.
- Improve x86 JIT's codegen for PROBE_MEM runtime error checks.
- Remove the need for trace_printk_lock for bpf_trace_printk and
bpf_trace_vprintk helpers.
- Extend libbpf's bpf_tracing.h support for tracing arguments of
kprobes/uprobes and syscall as a special case.
- Significantly reduce the search time for module symbols by
livepatch and BPF.
- Enable cpumasks to be used as kptrs, which is useful for tracing
programs tracking which tasks end up running on which CPUs in
different time intervals.
- Add support for BPF trampoline on s390x and riscv64.
- Add capability to export the XDP features supported by the NIC.
- Add __bpf_kfunc tag for marking kernel functions as kfuncs.
- Add cgroup.memory=nobpf kernel parameter option to disable BPF
memory accounting for container environments.
Netfilter:
- Remove the CLUSTERIP target. It has been marked as obsolete for
years, and we still have WARN splats wrt races of the out-of-band
/proc interface installed by this target.
- Add 'destroy' commands to nf_tables. They are identical to the
existing 'delete' commands, but do not return an error if the
referenced object (set, chain, rule...) did not exist.
Driver API:
- Improve cpumask_local_spread() locality to help NICs set the right
IRQ affinity on AMD platforms.
- Separate C22 and C45 MDIO bus transactions more clearly.
- Introduce new DCB table to control DSCP rewrite on egress.
- Support configuration of Physical Layer Collision Avoidance (PLCA)
Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
shared medium Ethernet.
- Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
preemption of low priority frames by high priority frames.
- Add support for controlling MACSec offload using netlink SET.
- Rework devlink instance refcounts to allow registration and
de-registration under the instance lock. Split the code into
multiple files, drop some of the unnecessarily granular locks and
factor out common parts of netlink operation handling.
- Add TX frame aggregation parameters (for USB drivers).
- Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
messages with notifications for debug.
- Allow offloading of UDP NEW connections via act_ct.
- Add support for per action HW stats in TC.
- Support hardware miss to TC action (continue processing in SW from
a specific point in the action chain).
- Warn if old Wireless Extension user space interface is used with
modern cfg80211/mac80211 drivers. Do not support Wireless
Extensions for Wi-Fi 7 devices at all. Everyone should switch to
using nl80211 interface instead.
- Improve the CAN bit timing configuration. Use extack to return
error messages directly to user space, update the SJW handling,
including the definition of a new default value that will benefit
CAN-FD controllers, by increasing their oscillator tolerance.
New hardware / drivers:
- Ethernet:
- nVidia BlueField-3 support (control traffic driver)
- Ethernet support for imx93 SoCs
- Motorcomm yt8531 gigabit Ethernet PHY
- onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
- Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
- Amlogic gxl MDIO mux
- WiFi:
- RealTek RTL8188EU (rtl8xxxu)
- Qualcomm Wi-Fi 7 devices (ath12k)
- CAN:
- Renesas R-Car V4H
Drivers:
- Bluetooth:
- Set Per Platform Antenna Gain (PPAG) for Intel controllers.
- Ethernet NICs:
- Intel (1G, igc):
- support TSN / Qbv / packet scheduling features of i226 model
- Intel (100G, ice):
- use GNSS subsystem instead of TTY
- multi-buffer XDP support
- extend support for GPIO pins to E823 devices
- nVidia/Mellanox:
- update the shared buffer configuration on PFC commands
- implement PTP adjphase function for HW offset control
- TC support for Geneve and GRE with VF tunnel offload
- more efficient crypto key management method
- multi-port eswitch support
- Netronome/Corigine:
- add DCB IEEE support
- support IPsec offloading for NFP3800
- Freescale/NXP (enetc):
- support XDP_REDIRECT for XDP non-linear buffers
- improve reconfig, avoid link flap and waiting for idle
- support MAC Merge layer
- Other NICs:
- sfc/ef100: add basic devlink support for ef100
- ionic: rx_push mode operation (writing descriptors via MMIO)
- bnxt: use the auxiliary bus abstraction for RDMA
- r8169: disable ASPM and reset bus in case of tx timeout
- cpsw: support QSGMII mode for J721e CPSW9G
- cpts: support pulse-per-second output
- ngbe: add an mdio bus driver
- usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
- r8152: handle devices with FW with NCM support
- amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
- virtio-net: support multi buffer XDP
- virtio/vsock: replace virtio_vsock_pkt with sk_buff
- tsnep: XDP support
- Ethernet high-speed switches:
- nVidia/Mellanox (mlxsw):
- add support for latency TLV (in FW control messages)
- Microchip (sparx5):
- separate explicit and implicit traffic forwarding rules, make
the implicit rules always active
- add support for egress DSCP rewrite
- IS0 VCAP support (Ingress Classification)
- IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
etc.)
- ES2 VCAP support (Egress Access Control)
- support for Per-Stream Filtering and Policing (802.1Q,
8.6.5.1)
- Ethernet embedded switches:
- Marvell (mv88e6xxx):
- add MAB (port auth) offload support
- enable PTP receive for mv88e6390
- NXP (ocelot):
- support MAC Merge layer
- support for the the vsc7512 internal copper phys
- Microchip:
- lan9303: convert to PHYLINK
- lan966x: support TC flower filter statistics
- lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
- lan937x: support Credit Based Shaper configuration
- ksz9477: support Energy Efficient Ethernet
- other:
- qca8k: convert to regmap read/write API, use bulk operations
- rswitch: Improve TX timestamp accuracy
- Intel WiFi (iwlwifi):
- EHT (Wi-Fi 7) rate reporting
- STEP equalizer support: transfer some STEP (connection to radio
on platforms with integrated wifi) related parameters from the
BIOS to the firmware.
- Qualcomm 802.11ax WiFi (ath11k):
- IPQ5018 support
- Fine Timing Measurement (FTM) responder role support
- channel 177 support
- MediaTek WiFi (mt76):
- per-PHY LED support
- mt7996: EHT (Wi-Fi 7) support
- Wireless Ethernet Dispatch (WED) reset support
- switch to using page pool allocator
- RealTek WiFi (rtw89):
- support new version of Bluetooth co-existance
- Mobile:
- rmnet: support TX aggregation"
* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
page_pool: add a comment explaining the fragment counter usage
net: ethtool: fix __ethtool_dev_mm_supported() implementation
ethtool: pse-pd: Fix double word in comments
xsk: add linux/vmalloc.h to xsk.c
sefltests: netdevsim: wait for devlink instance after netns removal
selftest: fib_tests: Always cleanup before exit
net/mlx5e: Align IPsec ASO result memory to be as required by hardware
net/mlx5e: TC, Set CT miss to the specific ct action instance
net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
net/mlx5: Refactor tc miss handling to a single function
net/mlx5: Kconfig: Make tc offload depend on tc skb extension
net/sched: flower: Support hardware miss to tc action
net/sched: flower: Move filter handle initialization earlier
net/sched: cls_api: Support hardware miss to tc action
net/sched: Rename user cookie and act cookie
sfc: fix builds without CONFIG_RTC_LIB
sfc: clean up some inconsistent indentings
net/mlx4_en: Introduce flexible array to silence overflow warning
net: lan966x: Fix possible deadlock inside PTP
net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
...
Diffstat (limited to 'Documentation/translations/zh_CN/core-api/kref.rst')
-rw-r--r-- | Documentation/translations/zh_CN/core-api/kref.rst | 311 |
1 files changed, 311 insertions, 0 deletions
diff --git a/Documentation/translations/zh_CN/core-api/kref.rst b/Documentation/translations/zh_CN/core-api/kref.rst new file mode 100644 index 000000000..b9902af31 --- /dev/null +++ b/Documentation/translations/zh_CN/core-api/kref.rst @@ -0,0 +1,311 @@ +.. include:: ../disclaimer-zh_CN.rst + +:Original: Documentation/core-api/kref.rst + +翻译: + +司延腾 Yanteng Si <siyanteng@loongson.cn> + +校译: + + <此处请校译员签名(自愿),我将在下一个版本添加> + +.. _cn_core_api_kref.rst: + +================================= +为内核对象添加引用计数器(krefs) +================================= + +:作者: Corey Minyard <minyard@acm.org> +:作者: Thomas Hellstrom <thellstrom@vmware.com> + +其中很多内容都是从Greg Kroah-Hartman2004年关于krefs的OLS论文和演讲中摘 +录的,可以在以下网址找到: + + - http://www.kroah.com/linux/talks/ols_2004_kref_paper/Reprint-Kroah-Hartman-OLS2004.pdf + - http://www.kroah.com/linux/talks/ols_2004_kref_talk/ + +简介 +==== + +krefs允许你为你的对象添加引用计数器。如果你有在多个地方使用和传递的对象, +而你没有refcounts,你的代码几乎肯定是坏的。如果你想要引用计数,krefs是个 +好办法。 + +要使用kref,请在你的数据结构中添加一个,如:: + + struct my_data + { + . + . + struct kref refcount; + . + . + }; + +kref可以出现在数据结构体中的任何地方。 + +初始化 +====== + +你必须在分配kref之后初始化它。 要做到这一点,可以这样调用kref_init:: + + struct my_data *data; + + data = kmalloc(sizeof(*data), GFP_KERNEL); + if (!data) + return -ENOMEM; + kref_init(&data->refcount); + +这将kref中的refcount设置为1。 + +Kref规则 +======== + +一旦你有一个初始化的kref,你必须遵循以下规则: + +1) 如果你对一个指针做了一个非临时性的拷贝,特别是如果它可以被传递给另一个执 + 行线程,你必须在传递之前用kref_get()增加refcount:: + + kref_get(&data->refcount); + + 如果你已经有了一个指向kref-ed结构体的有效指针(refcount不能为零),你 + 可以在没有锁的情况下这样做。 + +2) 当你完成对一个指针的处理时,你必须调用kref_put():: + + kref_put(&data->refcount, data_release); + + 如果这是对该指针的最后一次引用,释放程序将被调用。如果代码从来没有尝试过 + 在没有已经持有有效指针的情况下获得一个kref-ed结构体的有效指针,那么在没 + 有锁的情况下这样做是安全的。 + +3) 如果代码试图获得对一个kref-ed结构体的引用,而不持有一个有效的指针,它必 + 须按顺序访问,在kref_put()期间不能发生kref_get(),并且该结构体在kref_get() + 期间必须保持有效。 + +例如,如果你分配了一些数据,然后将其传递给另一个线程来处理:: + + void data_release(struct kref *ref) + { + struct my_data *data = container_of(ref, struct my_data, refcount); + kfree(data); + } + + void more_data_handling(void *cb_data) + { + struct my_data *data = cb_data; + . + . do stuff with data here + . + kref_put(&data->refcount, data_release); + } + + int my_data_handler(void) + { + int rv = 0; + struct my_data *data; + struct task_struct *task; + data = kmalloc(sizeof(*data), GFP_KERNEL); + if (!data) + return -ENOMEM; + kref_init(&data->refcount); + + kref_get(&data->refcount); + task = kthread_run(more_data_handling, data, "more_data_handling"); + if (task == ERR_PTR(-ENOMEM)) { + rv = -ENOMEM; + kref_put(&data->refcount, data_release); + goto out; + } + + . + . do stuff with data here + . + out: + kref_put(&data->refcount, data_release); + return rv; + } + +这样,两个线程处理数据的顺序并不重要,kref_put()处理知道数据不再被引用并释 +放它。kref_get()不需要锁,因为我们已经有了一个有效的指针,我们拥有一个 +refcount。put不需要锁,因为没有任何东西试图在没有持有指针的情况下获取数据。 + +在上面的例子中,kref_put()在成功和错误路径中都会被调用2次。这是必要的,因 +为引用计数被kref_init()和kref_get()递增了2次。 + +请注意,规则1中的 "before "是非常重要的。你不应该做类似于:: + + task = kthread_run(more_data_handling, data, "more_data_handling"); + if (task == ERR_PTR(-ENOMEM)) { + rv = -ENOMEM; + goto out; + } else + /* BAD BAD BAD - 在交接后得到 */ + kref_get(&data->refcount); + +不要以为你知道自己在做什么而使用上述构造。首先,你可能不知道自己在做什么。 +其次,你可能知道自己在做什么(有些情况下涉及到锁,上述做法可能是合法的), +但其他不知道自己在做什么的人可能会改变代码或复制代码。这是很危险的作风。请 +不要这样做。 + +在有些情况下,你可以优化get和put。例如,如果你已经完成了一个对象,并且给其 +他对象排队,或者把它传递给其他对象,那么就没有理由先做一个get,然后再做一个 +put:: + + /* 糟糕的额外获取(get)和输出(put) */ + kref_get(&obj->ref); + enqueue(obj); + kref_put(&obj->ref, obj_cleanup); + +只要做enqueue就可以了。 我们随时欢迎对这个问题的评论:: + + enqueue(obj); + /* 我们已经完成了对obj的处理,所以我们把我们的refcount传给了队列。 + 在这之后不要再碰obj了! */ + +最后一条规则(规则3)是最难处理的一条。例如,你有一个每个项目都被krefed的列表, +而你希望得到第一个项目。你不能只是从列表中抽出第一个项目,然后kref_get()它。 +这违反了规则3,因为你还没有持有一个有效的指针。你必须添加一个mutex(或其他锁)。 +比如说:: + + static DEFINE_MUTEX(mutex); + static LIST_HEAD(q); + struct my_data + { + struct kref refcount; + struct list_head link; + }; + + static struct my_data *get_entry() + { + struct my_data *entry = NULL; + mutex_lock(&mutex); + if (!list_empty(&q)) { + entry = container_of(q.next, struct my_data, link); + kref_get(&entry->refcount); + } + mutex_unlock(&mutex); + return entry; + } + + static void release_entry(struct kref *ref) + { + struct my_data *entry = container_of(ref, struct my_data, refcount); + + list_del(&entry->link); + kfree(entry); + } + + static void put_entry(struct my_data *entry) + { + mutex_lock(&mutex); + kref_put(&entry->refcount, release_entry); + mutex_unlock(&mutex); + } + +如果你不想在整个释放操作过程中持有锁,kref_put()的返回值是有用的。假设你不想在 +上面的例子中在持有锁的情况下调用kfree()(因为这样做有点无意义)。你可以使用kref_put(), +如下所示:: + + static void release_entry(struct kref *ref) + { + /* 所有的工作都是在从kref_put()返回后完成的。*/ + } + + static void put_entry(struct my_data *entry) + { + mutex_lock(&mutex); + if (kref_put(&entry->refcount, release_entry)) { + list_del(&entry->link); + mutex_unlock(&mutex); + kfree(entry); + } else + mutex_unlock(&mutex); + } + +如果你必须调用其他程序作为释放操作的一部分,而这些程序可能需要很长的时间,或者可 +能要求相同的锁,那么这真的更有用。请注意,在释放例程中做所有的事情还是比较好的, +因为它比较整洁。 + +上面的例子也可以用kref_get_unless_zero()来优化,方法如下:: + + static struct my_data *get_entry() + { + struct my_data *entry = NULL; + mutex_lock(&mutex); + if (!list_empty(&q)) { + entry = container_of(q.next, struct my_data, link); + if (!kref_get_unless_zero(&entry->refcount)) + entry = NULL; + } + mutex_unlock(&mutex); + return entry; + } + + static void release_entry(struct kref *ref) + { + struct my_data *entry = container_of(ref, struct my_data, refcount); + + mutex_lock(&mutex); + list_del(&entry->link); + mutex_unlock(&mutex); + kfree(entry); + } + + static void put_entry(struct my_data *entry) + { + kref_put(&entry->refcount, release_entry); + } + +这对于在put_entry()中移除kref_put()周围的mutex锁是很有用的,但是重要的是 +kref_get_unless_zero被封装在查找表中的同一关键部分,否则kref_get_unless_zero +可能引用已经释放的内存。注意,在不检查其返回值的情况下使用kref_get_unless_zero +是非法的。如果你确信(已经有了一个有效的指针)kref_get_unless_zero()会返回true, +那么就用kref_get()代替。 + +Krefs和RCU +========== + +函数kref_get_unless_zero也使得在上述例子中使用rcu锁进行查找成为可能:: + + struct my_data + { + struct rcu_head rhead; + . + struct kref refcount; + . + . + }; + + static struct my_data *get_entry_rcu() + { + struct my_data *entry = NULL; + rcu_read_lock(); + if (!list_empty(&q)) { + entry = container_of(q.next, struct my_data, link); + if (!kref_get_unless_zero(&entry->refcount)) + entry = NULL; + } + rcu_read_unlock(); + return entry; + } + + static void release_entry_rcu(struct kref *ref) + { + struct my_data *entry = container_of(ref, struct my_data, refcount); + + mutex_lock(&mutex); + list_del_rcu(&entry->link); + mutex_unlock(&mutex); + kfree_rcu(entry, rhead); + } + + static void put_entry(struct my_data *entry) + { + kref_put(&entry->refcount, release_entry_rcu); + } + +但要注意的是,在调用release_entry_rcu后,结构kref成员需要在有效内存中保留一个rcu +宽限期。这可以通过使用上面的kfree_rcu(entry, rhead)来实现,或者在使用kfree之前 +调用synchronize_rcu(),但注意synchronize_rcu()可能会睡眠相当长的时间。 |