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author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-06-07 17:27:45 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-06-07 17:27:45 -0700 |
commit | af7b4801030c07637840191c69eb666917e4135d (patch) | |
tree | d4238c6c1fe6c06112f766ae5a90afde53644f78 /include/linux/u64_stats_sync.h | |
parent | Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-next (diff) | |
parent | net: dsa: lantiq_gswip: fix and improve the unsupported interface error (diff) | |
download | wireguard-linux-af7b4801030c07637840191c69eb666917e4135d.tar.xz wireguard-linux-af7b4801030c07637840191c69eb666917e4135d.zip |
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Pull networking fixes from David Miller:
- Fix the build with certain Kconfig combinations for the Chelsio
inline TLS device, from Rohit Maheshwar and Vinay Kumar Yadavi.
- Fix leak in genetlink, from Cong Lang.
- Fix out of bounds packet header accesses in seg6, from Ahmed
Abdelsalam.
- Two XDP fixes in the ENA driver, from Sameeh Jubran
- Use rwsem in device rename instead of a seqcount because this code
can sleep, from Ahmed S. Darwish.
- Fix WoL regressions in r8169, from Heiner Kallweit.
- Fix qed crashes in kdump mode, from Alok Prasad.
- Fix the callbacks used for certain thermal zones in mlxsw, from Vadim
Pasternak.
* git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (35 commits)
net: dsa: lantiq_gswip: fix and improve the unsupported interface error
mlxsw: core: Use different get_trend() callbacks for different thermal zones
net: dp83869: Reset return variable if PHY strap is read
rhashtable: Drop raw RCU deref in nested_table_free
cxgb4: Use kfree() instead kvfree() where appropriate
net: qed: fixes crash while running driver in kdump kernel
vsock/vmci: make vmci_vsock_transport_cb() static
net: ethtool: Fix comment mentioning typo in IS_ENABLED()
net: phy: mscc: fix Serdes configuration in vsc8584_config_init
net: mscc: Fix OF_MDIO config check
net: marvell: Fix OF_MDIO config check
net: dp83867: Fix OF_MDIO config check
net: dp83869: Fix OF_MDIO config check
net: ethernet: mvneta: fix MVNETA_SKB_HEADROOM alignment
ethtool: linkinfo: remove an unnecessary NULL check
net/xdp: use shift instead of 64 bit division
crypto/chtls:Fix compile error when CONFIG_IPV6 is disabled
inet_connection_sock: clear inet_num out of destroy helper
yam: fix possible memory leak in yam_init_driver
lan743x: Use correct MAC_CR configuration for 1 GBit speed
...
Diffstat (limited to 'include/linux/u64_stats_sync.h')
-rw-r--r-- | include/linux/u64_stats_sync.h | 43 |
1 files changed, 23 insertions, 20 deletions
diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h index 9de5c10293f5..c6abb79501b3 100644 --- a/include/linux/u64_stats_sync.h +++ b/include/linux/u64_stats_sync.h @@ -3,33 +3,36 @@ #define _LINUX_U64_STATS_SYNC_H /* - * To properly implement 64bits network statistics on 32bit and 64bit hosts, - * we provide a synchronization point, that is a noop on 64bit or UP kernels. + * Protect against 64-bit values tearing on 32-bit architectures. This is + * typically used for statistics read/update in different subsystems. * * Key points : - * 1) Use a seqcount on SMP 32bits, with low overhead. - * 2) Whole thing is a noop on 64bit arches or UP kernels. - * 3) Write side must ensure mutual exclusion or one seqcount update could + * + * - Use a seqcount on 32-bit SMP, only disable preemption for 32-bit UP. + * - The whole thing is a no-op on 64-bit architectures. + * + * Usage constraints: + * + * 1) Write side must ensure mutual exclusion, or one seqcount update could * be lost, thus blocking readers forever. - * If this synchronization point is not a mutex, but a spinlock or - * spinlock_bh() or disable_bh() : - * 3.1) Write side should not sleep. - * 3.2) Write side should not allow preemption. - * 3.3) If applicable, interrupts should be disabled. * - * 4) If reader fetches several counters, there is no guarantee the whole values - * are consistent (remember point 1) : this is a noop on 64bit arches anyway) + * 2) Write side must disable preemption, or a seqcount reader can preempt the + * writer and also spin forever. + * + * 3) Write side must use the _irqsave() variant if other writers, or a reader, + * can be invoked from an IRQ context. * - * 5) readers are allowed to sleep or be preempted/interrupted : They perform - * pure reads. But if they have to fetch many values, it's better to not allow - * preemptions/interruptions to avoid many retries. + * 4) If reader fetches several counters, there is no guarantee the whole values + * are consistent w.r.t. each other (remember point #2: seqcounts are not + * used for 64bit architectures). * - * 6) If counter might be written by an interrupt, readers should block interrupts. - * (On UP, there is no seqcount_t protection, a reader allowing interrupts could - * read partial values) + * 5) Readers are allowed to sleep or be preempted/interrupted: they perform + * pure reads. * - * 7) For irq and softirq uses, readers can use u64_stats_fetch_begin_irq() and - * u64_stats_fetch_retry_irq() helpers + * 6) Readers must use both u64_stats_fetch_{begin,retry}_irq() if the stats + * might be updated from a hardirq or softirq context (remember point #1: + * seqcounts are not used for UP kernels). 32-bit UP stat readers could read + * corrupted 64-bit values otherwise. * * Usage : * |