# # IrDA protocol configuration # menuconfig IRDA depends on NET && !S390 tristate "IrDA (infrared) subsystem support" select CRC_CCITT ---help--- Say Y here if you want to build support for the IrDA (TM) protocols. The Infrared Data Associations (tm) specifies standards for wireless infrared communication and is supported by most laptops and PDA's. To use Linux support for the IrDA (tm) protocols, you will also need some user-space utilities like irattach. For more information, see the file . You also want to read the IR-HOWTO, available at . If you want to exchange bits of data (vCal, vCard) with a PDA, you will need to install some OBEX application, such as OpenObex : To compile this support as a module, choose M here: the module will be called irda. comment "IrDA protocols" depends on IRDA source "net/irda/irlan/Kconfig" source "net/irda/irnet/Kconfig" source "net/irda/ircomm/Kconfig" config IRDA_ULTRA bool "Ultra (connectionless) protocol" depends on IRDA help Say Y here to support the connectionless Ultra IRDA protocol. Ultra allows to exchange data over IrDA with really simple devices (watch, beacon) without the overhead of the IrDA protocol (no handshaking, no management frames, simple fixed header). Ultra is available as a special socket : socket(AF_IRDA, SOCK_DGRAM, 1); comment "IrDA options" depends on IRDA config IRDA_CACHE_LAST_LSAP bool "Cache last LSAP" depends on IRDA help Say Y here if you want IrLMP to cache the last LSAP used. This makes sense since most frames will be sent/received on the same connection. Enabling this option will save a hash-lookup per frame. If unsure, say Y. config IRDA_FAST_RR bool "Fast RRs (low latency)" depends on IRDA ---help--- Say Y here is you want IrLAP to send fast RR (Receive Ready) frames when acting as a primary station. Disabling this option will make latency over IrDA very bad. Enabling this option will make the IrDA stack send more packet than strictly necessary, thus reduce your battery life (but not that much). Fast RR will make IrLAP send out a RR frame immediately when receiving a frame if its own transmit queue is currently empty. This will give a lot of speed improvement when receiving much data since the secondary station will not have to wait the max. turn around time (usually 500ms) before it is allowed to transmit the next time. If the transmit queue of the secondary is also empty, the primary will start backing-off before sending another RR frame, waiting longer each time until the back-off reaches the max. turn around time. This back-off increase in controlled via /proc/sys/net/irda/fast_poll_increase If unsure, say Y. config IRDA_DEBUG bool "Debug information" depends on IRDA help Say Y here if you want the IrDA subsystem to write debug information to your syslog. You can change the debug level in /proc/sys/net/irda/debug . When this option is enabled, the IrDA also perform many extra internal verifications which will usually prevent the kernel to crash in case of bugs. If unsure, say Y (since it makes it easier to find the bugs). source "drivers/net/irda/Kconfig" ass='ctrl'>space:mode:
authorDouglas Miller <dougmill@linux.vnet.ibm.com>2017-01-28 06:42:20 -0600
committerTejun Heo <tj@kernel.org>2017-01-28 07:49:42 -0500
commit966d2b04e070bc040319aaebfec09e0144dc3341 (patch)
tree4b96156e3d1dd4dfd6039b7c219c9dc4616da52d /net/ipv4/syncookies.c
parent1b1bc42c1692e9b62756323c675a44cb1a1f9dbd (diff)
percpu-refcount: fix reference leak during percpu-atomic transition
percpu_ref_tryget() and percpu_ref_tryget_live() should return "true" IFF they acquire a reference. But the return value from atomic_long_inc_not_zero() is a long and may have high bits set, e.g. PERCPU_COUNT_BIAS, and the return value of the tryget routines is bool so the reference may actually be acquired but the routines return "false" which results in a reference leak since the caller assumes it does not need to do a corresponding percpu_ref_put(). This was seen when performing CPU hotplug during I/O, as hangs in blk_mq_freeze_queue_wait where percpu_ref_kill (blk_mq_freeze_queue_start) raced with percpu_ref_tryget (blk_mq_timeout_work). Sample stack trace: __switch_to+0x2c0/0x450 __schedule+0x2f8/0x970 schedule+0x48/0xc0 blk_mq_freeze_queue_wait+0x94/0x120 blk_mq_queue_reinit_work+0xb8/0x180 blk_mq_queue_reinit_prepare+0x84/0xa0 cpuhp_invoke_callback+0x17c/0x600 cpuhp_up_callbacks+0x58/0x150 _cpu_up+0xf0/0x1c0 do_cpu_up+0x120/0x150 cpu_subsys_online+0x64/0xe0 device_online+0xb4/0x120 online_store+0xb4/0xc0 dev_attr_store+0x68/0xa0 sysfs_kf_write+0x80/0xb0 kernfs_fop_write+0x17c/0x250 __vfs_write+0x6c/0x1e0 vfs_write+0xd0/0x270 SyS_write+0x6c/0x110 system_call+0x38/0xe0 Examination of the queue showed a single reference (no PERCPU_COUNT_BIAS, and __PERCPU_REF_DEAD, __PERCPU_REF_ATOMIC set) and no requests. However, conditions at the time of the race are count of PERCPU_COUNT_BIAS + 0 and __PERCPU_REF_DEAD and __PERCPU_REF_ATOMIC set. The fix is to make the tryget routines use an actual boolean internally instead of the atomic long result truncated to a int. Fixes: e625305b3907 percpu-refcount: make percpu_ref based on longs instead of ints Link: https://bugzilla.kernel.org/show_bug.cgi?id=190751 Signed-off-by: Douglas Miller <dougmill@linux.vnet.ibm.com> Reviewed-by: Jens Axboe <axboe@fb.com> Signed-off-by: Tejun Heo <tj@kernel.org> Fixes: e625305b3907 ("percpu-refcount: make percpu_ref based on longs instead of ints") Cc: stable@vger.kernel.org # v3.18+
Diffstat (limited to 'net/ipv4/syncookies.c')