user/sven/linux.git/include/linux/preempt.h, branch v4.2.4

sched/preempt: Fix cond_resched_lock() and cond_resched_softirq()

2015-10-22T21:49:35Z

commit fe32d3cd5e8eb0f82e459763374aa80797023403 upstream. These functions check should_resched() before unlocking spinlock/bh-enable: preempt_count always non-zero => should_resched() always returns false. cond_resched_lock() worked iff spin_needbreak is set. This patch adds argument "preempt_offset" to should_resched(). preempt_count offset constants for that: PREEMPT_DISABLE_OFFSET - offset after preempt_disable() PREEMPT_LOCK_OFFSET - offset after spin_lock() SOFTIRQ_DISABLE_OFFSET - offset after local_bh_distable() SOFTIRQ_LOCK_OFFSET - offset after spin_lock_bh() Signed-off-by: Konstantin Khlebnikov Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Graf Cc: Boris Ostrovsky Cc: David Vrabel Cc: Linus Torvalds Cc: Mike Galbraith Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: bdb438065890 ("sched: Extract the basic add/sub preempt_count modifiers") Link: http://lkml.kernel.org/r/20150715095204.12246.98268.stgit@buzz Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

sched, preempt_notifier: separate notifier registration from static_key inc/dec

2015-07-03T16:55:00Z

Commit 1cde2930e154 ("sched/preempt: Add static_key() to preempt_notifiers") had two problems. First, the preempt-notifier API needs to sleep with the addition of the static_key, we do however need to hold off preemption while modifying the preempt notifier list, otherwise a preemption could observe an inconsistent list state. KVM correctly registers and unregisters preempt notifiers with preemption disabled, so the sleep caused dmesg splats. Second, KVM registers and unregisters preemption notifiers very often (in vcpu_load/vcpu_put). With a single uniprocessor guest the static key would move between 0 and 1 continuously, hitting the slow path on every userspace exit. To fix this, wrap the static_key inc/dec in a new API, and call it from KVM. Fixes: 1cde2930e154 ("sched/preempt: Add static_key() to preempt_notifiers") Reported-by: Pontus Fuchs Reported-by: Takashi Iwai Tested-by: Takashi Iwai Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Paolo Bonzini

preempt: Reorganize the notrace definitions a bit

2015-06-07T13:57:43Z

preempt.h has two seperate "#ifdef CONFIG_PREEMPT" sections: one to define preempt_enable() and another to define preempt_enable_notrace(). Lets gather both. Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Fengguang Wu Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1433432349-1021-4-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar

preempt: Use preempt_schedule_context() as the official tracing preemption point

2015-06-07T13:57:42Z

preempt_schedule_context() is a tracing safe preemption point but it's only used when CONFIG_CONTEXT_TRACKING=y. Other configs have tracing recursion issues since commit: b30f0e3ffedf ("sched/preempt: Optimize preemption operations on __schedule() callers") introduced function based preemp_count_*() ops. Lets make it available on all configs and give it a more appropriate name for its new position. Reported-by: Fengguang Wu Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1433432349-1021-3-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar

sched/preempt: Remove PREEMPT_ACTIVE unmasking off in_atomic()

2015-05-19T06:39:13Z

Now that PREEMPT_ACTIVE implies PREEMPT_DISABLE_OFFSET, ignoring PREEMPT_ACTIVE from in_atomic() check isn't useful anymore. Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1431441711-29753-7-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar

sched/preempt: Fix out of date comment

2015-05-19T06:39:13Z

Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1431441711-29753-6-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar

sched/preempt: Optimize preemption operations on __schedule() callers

2015-05-19T06:39:12Z

__schedule() disables preemption and some of its callers (the preempt_schedule*() family) also set PREEMPT_ACTIVE. So we have two preempt_count() modifications that could be performed at once. Lets remove the preemption disablement from __schedule() and pull this responsibility to its callers in order to optimize preempt_count() operations in a single place. Suggested-by: Linus Torvalds Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1431441711-29753-5-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar

sched/preempt: Rename PREEMPT_CHECK_OFFSET to PREEMPT_DISABLE_OFFSET

2015-05-19T06:39:12Z

"CHECK" suggests it's only used as a comparison mask. But now it's used further as a config-conditional preempt disabler offset. Lets disambiguate this name. Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1431441711-29753-4-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar

sched/preempt: Rearrange a few symbols after headers merge

2015-05-19T06:39:12Z

Adjust a few comments, and further integrate a few definitions after the dumb headers copy. Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1431441711-29753-3-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar

sched/preempt: Merge preempt_mask.h into preempt.h

2015-05-19T06:39:11Z

preempt_mask.h defines all the preempt_count semantics and related symbols: preempt, softirq, hardirq, nmi, preempt active, need resched, etc... preempt.h defines the accessors and mutators of preempt_count. But there is a messy dependency game around those two header files: * preempt_mask.h includes preempt.h in order to access preempt_count() * preempt_mask.h defines all preempt_count semantic and symbols except PREEMPT_NEED_RESCHED that is needed by asm/preempt.h Thus we need to define it from preempt.h, right before including asm/preempt.h, instead of defining it to preempt_mask.h with the other preempt_count symbols. Therefore the preempt_count semantics happen to be spread out. * We plan to introduce preempt_active_[enter,exit]() to consolidate preempt_schedule*() code. But we'll need to access both preempt_count mutators (preempt_count_add()) and preempt_count symbols (PREEMPT_ACTIVE, PREEMPT_OFFSET). The usual place to define preempt operations is in preempt.h but then we'll need symbols in preempt_mask.h which already includes preempt.h. So we end up with a ressource circle dependency. Lets merge preempt_mask.h into preempt.h to solve these dependency issues. This way we gather semantic symbols and operation definition of preempt_count in a single file. This is a dumb copy-paste merge. Further merge re-arrangments are performed in a subsequent patch to ease review. Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1431441711-29753-2-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar