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2016-10-11relay: Use irq_work instead of plain timer for deferred wakeupPeter Zijlstra1-1/+2
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 <[email protected]> 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. [[email protected]: select CONFIG_IRQ_WORK] Link: http://lkml.kernel.org/r/[email protected] [[email protected]: coding-style fixes] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Peter Zijlstra <[email protected]> Signed-off-by: Akash Goel <[email protected]> Cc: Tom Zanussi <[email protected]> Cc: Chris Wilson <[email protected]> Cc: Tvrtko Ursulin <[email protected]> Signed-off-by: Arnd Bergmann <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
2016-09-06relayfs: Convert to hotplug state machineRichard Weinberger1-0/+6
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 <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> Reviewed-by: Sebastian Andrzej Siewior <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: [email protected] Cc: Andrew Morton <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Thomas Gleixner <[email protected]>
2016-09-06relay: Use per CPU constructs for the relay channel buffer pointersAkash Goel1-7/+10
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 <[email protected]> Reviewed-by: Chris Wilson <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]>
2013-04-30kernel/relay.c: move FIX_SIZE macro into relay.czhangwei(Jovi)1-3/+0
It's better to place FIX_SIZE macro in relay.c, instead of relay.h Signed-off-by: zhangwei(Jovi) <[email protected]> Cc: Jens Axboe <[email protected]> Cc: Al Viro <[email protected]> Cc: Eric Dumazet <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
2012-03-04BUG: headers with BUG/BUG_ON etc. need linux/bug.hPaul Gortmaker1-0/+1
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 <linux/bug.h> 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 <[email protected]>
2012-01-03switch debugfs to umode_tAl Viro1-1/+1
Signed-off-by: Al Viro <[email protected]>
2009-09-24docs: fix various Documentation/ paths in header filesRandy Dunlap1-1/+1
Fix various Documentation/ paths in include/linux/. Signed-off-by: Randy Dunlap <[email protected]> Reviewed-by: Jesper Juhl <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
2008-07-26relay: add buffer-only channels; useful for early loggingEduard - Gabriel Munteanu1-0/+5
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. [[email protected]: build fix] Signed-off-by: Eduard - Gabriel Munteanu <[email protected]> Cc: Tom Zanussi <[email protected]> Signed-off-by: KOSAKI Motohiro <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
2007-05-09relay: use plain timer instead of delayed workTom Zanussi1-1/+2
relay doesn't need to use schedule_delayed_work() for waking readers when a simple timer will do. Signed-off-by: Tom Zanussi <[email protected]> Cc: Satyam Sharma <[email protected]> Cc: Oleg Nesterov <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
2007-02-11[PATCH] Relay: add CPU hotplug supportMathieu Desnoyers1-2/+7
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. [[email protected]: avoid lock_cpu_hotplug deadlock] Signed-off-by: Mathieu Desnoyers <[email protected]> Cc: Tom Zanussi <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
2006-12-07[PATCH] struct seq_operations and struct file_operations constificationHelge Deller1-1/+1
- move some file_operations structs into the .rodata section - move static strings from policy_types[] array into the .rodata section - fix generic seq_operations usages, so that those structs may be defined as "const" as well [[email protected]: couple of fixes] Signed-off-by: Helge Deller <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
2006-11-22WorkStruct: make allyesconfigDavid Howells1-1/+1
Fix up for make allyesconfig. Signed-Off-By: David Howells <[email protected]>
2006-04-26Don't include linux/config.h from anywhere else in include/David Woodhouse1-1/+0
Signed-off-by: David Woodhouse <[email protected]>
2006-03-23[PATCH] relay: migrate from relayfs to a generic relay APIJens Axboe1-0/+281
Original patch from Paul Mundt, sysfs parts removed by me since they were broken. Signed-off-by: Jens Axboe <[email protected]>
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