user/sven/linux.git/include/linux/relay.h, branch v4.9.140

relay: Use irq_work instead of plain timer for deferred wakeup

2016-10-11T22:06:32Z

Relay avoids calling wake_up_interruptible() for doing the wakeup of readers/consumers, waiting for the generation of new data, from the context of a process which produced the data. This is apparently done to prevent the possibility of a deadlock in case Scheduler itself is is generating data for the relay, after acquiring rq->lock. The following patch used a timer (to be scheduled at next jiffy), for delegating the wakeup to another context. commit 7c9cb38302e78d24e37f7d8a2ea7eed4ae5f2fa7 Author: Tom Zanussi Date: Wed May 9 02:34:01 2007 -0700 relay: use plain timer instead of delayed work relay doesn't need to use schedule_delayed_work() for waking readers when a simple timer will do. Scheduling a plain timer, at next jiffies boundary, to do the wakeup causes a significant wakeup latency for the Userspace client, which makes relay less suitable for the high-frequency low-payload use cases where the data gets generated at a very high rate, like multiple sub buffers getting filled within a milli second. Moreover the timer is re-scheduled on every newly produced sub buffer so the timer keeps getting pushed out if sub buffers are filled in a very quick succession (less than a jiffy gap between filling of 2 sub buffers). As a result relay runs out of sub buffers to store the new data. By using irq_work it is ensured that wakeup of userspace client, blocked in the poll call, is done at earliest (through self IPI or next timer tick) enabling it to always consume the data in time. Also this makes relay consistent with printk & ring buffers (trace), as they too use irq_work for deferred wake up of readers. [arnd@arndb.de: select CONFIG_IRQ_WORK] Link: http://lkml.kernel.org/r/20160912154035.3222156-1-arnd@arndb.de [akpm@linux-foundation.org: coding-style fixes] Link: http://lkml.kernel.org/r/1472906487-1559-1-git-send-email-akash.goel@intel.com Signed-off-by: Peter Zijlstra Signed-off-by: Akash Goel Cc: Tom Zanussi Cc: Chris Wilson Cc: Tvrtko Ursulin Signed-off-by: Arnd Bergmann Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

relayfs: Convert to hotplug state machine

2016-09-06T16:30:20Z

Install the callbacks via the state machine. They are installed at run time but relay_prepare_cpu() does not need to be invoked by the boot CPU because relay_open() was not yet invoked and there are no pools that need to be created. Signed-off-by: Richard Weinberger Signed-off-by: Thomas Gleixner Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Sebastian Andrzej Siewior Cc: Peter Zijlstra Cc: rt@linutronix.de Cc: Andrew Morton Link: http://lkml.kernel.org/r/20160818125731.27256-3-bigeasy@linutronix.de Signed-off-by: Thomas Gleixner

relay: Use per CPU constructs for the relay channel buffer pointers

2016-09-06T16:30:19Z

relay essentially needs to maintain a per CPU array of channel buffer pointers but it manually creates that array. Instead its better to use the per CPU constructs, provided by the kernel, to allocate & access the array of pointer to channel buffers. Signed-off-by: Akash Goel Reviewed-by: Chris Wilson Link: http://lkml.kernel.org/r/1470909140-25919-1-git-send-email-akash.goel@intel.com Signed-off-by: Andrew Morton Signed-off-by: Thomas Gleixner

kernel/relay.c: move FIX_SIZE macro into relay.c

2013-05-01T00:04:09Z

It's better to place FIX_SIZE macro in relay.c, instead of relay.h Signed-off-by: zhangwei(Jovi) Cc: Jens Axboe Cc: Al Viro Cc: Eric Dumazet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

BUG: headers with BUG/BUG_ON etc. need linux/bug.h

2012-03-04T22:54:34Z

If a header file is making use of BUG, BUG_ON, BUILD_BUG_ON, or any other BUG variant in a static inline (i.e. not in a #define) then that header really should be including and not just expecting it to be implicitly present. We can make this change risk-free, since if the files using these headers didn't have exposure to linux/bug.h already, they would have been causing compile failures/warnings. Signed-off-by: Paul Gortmaker

switch debugfs to umode_t

2012-01-04T03:54:56Z

Signed-off-by: Al Viro

docs: fix various Documentation/ paths in header files

2009-09-24T14:20:57Z

Fix various Documentation/ paths in include/linux/. Signed-off-by: Randy Dunlap Reviewed-by: Jesper Juhl Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

relay: add buffer-only channels; useful for early logging

2008-07-26T19:00:04Z

Allows one to create and use a channel with no associated files. Files can be initialized later. This is useful in scenarios such as logging in early code, before VFS is up. Therefore, such channels can be created and used as soon as kmem_cache_init() completed. This is needed by kmemtrace to do tracing in early kernel code. [kosaki.motohiro@jp.fujitsu.com: build fix] Signed-off-by: Eduard - Gabriel Munteanu Cc: Tom Zanussi Signed-off-by: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

relay: use plain timer instead of delayed work

2007-05-09T19:30:51Z

relay doesn't need to use schedule_delayed_work() for waking readers when a simple timer will do. Signed-off-by: Tom Zanussi Cc: Satyam Sharma Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

[PATCH] Relay: add CPU hotplug support

2007-02-11T18:51:28Z

Mathieu originally needed to add this for tracing Xen, but it's something that's needed for any application that can be tracing while cpus are added. unplug isn't supported by this patch. The thought was that at minumum a new buffer needs to be added when a cpu comes up, but it wasn't worth the effort to remove buffers on cpu down since they'd be freed soon anyway when the channel was closed. [zanussi@us.ibm.com: avoid lock_cpu_hotplug deadlock] Signed-off-by: Mathieu Desnoyers Cc: Tom Zanussi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds