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* preempt: Use preempt_schedule_context() as the official tracing preemption pointFrederic Weisbecker2015-06-071-5/+2
| | | | | | | | | | | | | | | | | | | | | | | | | 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 <fengguang.wu@intel.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1433432349-1021-3-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Kill task_preempt_count()Oleg Nesterov2014-10-281-3/+0
| | | | | | | | | | | | | | | | | | | | | | | task_preempt_count() is pointless if preemption counter is per-cpu, currently this is x86 only. It is only valid if the task is not running, and even in this case the only info it can provide is the state of PREEMPT_ACTIVE bit. Change its single caller to check p->on_rq instead, this should be the same if p->state != TASK_RUNNING, and kill this helper. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Kirill Tkhai <tkhai@yandex.ru> Cc: Alexander Graf <agraf@suse.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Christoph Lameter <cl@linux.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: linux-arch@vger.kernel.org Link: http://lkml.kernel.org/r/20141008183348.GC17495@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Remove PREEMPT_NEED_RESCHED from generic codePeter Zijlstra2013-12-111-24/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | While hunting a preemption issue with Alexander, Ben noticed that the currently generic PREEMPT_NEED_RESCHED stuff is horribly broken for load-store architectures. We currently rely on the IPI to fold TIF_NEED_RESCHED into PREEMPT_NEED_RESCHED, but when this IPI lands while we already have a load for the preempt-count but before the store, the store will erase the PREEMPT_NEED_RESCHED change. The current preempt-count only works on load-store archs because interrupts are assumed to be completely balanced wrt their preempt_count fiddling; the previous preempt_count load will match the preempt_count state after the interrupt and therefore nothing gets lost. This patch removes the PREEMPT_NEED_RESCHED usage from generic code and pushes it into x86 arch code; the generic code goes back to relying on TIF_NEED_RESCHED. Boot tested on x86_64 and compile tested on ppc64. Reported-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Reported-and-Tested-by: Alexander Graf <agraf@suse.de> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20131128132641.GP10022@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Revert need_resched() to look at TIF_NEED_RESCHEDPeter Zijlstra2013-09-281-8/+0
| | | | | | | | | | | | | | | | | | | | | Yuanhan reported a serious throughput regression in his pigz benchmark. Using the ftrace patch I found that several idle paths need more TLC before we can switch the generic need_resched() over to preempt_need_resched. The preemption paths benefit most from preempt_need_resched and do indeed use it; all other need_resched() users don't really care that much so reverting need_resched() back to tif_need_resched() is the simple and safe solution. Reported-by: Yuanhan Liu <yuanhan.liu@linux.intel.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Huang Ying <ying.huang@intel.com> Cc: lkp@linux.intel.com Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20130927153003.GF15690@laptop.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched, x86: Optimize the preempt_schedule() callPeter Zijlstra2013-09-251-0/+10
| | | | | | | | | | | | | | Remove the bloat of the C calling convention out of the preempt_enable() sites by creating an ASM wrapper which allows us to do an asm("call ___preempt_schedule") instead. calling.h bits by Andi Kleen Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-tk7xdi1cvvxewixzke8t8le1@git.kernel.org [ Fixed build error. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Extract the basic add/sub preempt_count modifiersPeter Zijlstra2013-09-251-0/+35
| | | | | | | | | | | | | | | | | | | | | | Rewrite the preempt_count macros in order to extract the 3 basic preempt_count value modifiers: __preempt_count_add() __preempt_count_sub() and the new: __preempt_count_dec_and_test() And since we're at it anyway, replace the unconventional $op_preempt_count names with the more conventional preempt_count_$op. Since these basic operators are equivalent to the previous _notrace() variants, do away with the _notrace() versions. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-ewbpdbupy9xpsjhg960zwbv8@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched: Create more preempt_count accessorsPeter Zijlstra2013-09-251-0/+14
| | | | | | | | | | | | | | | | | We need a few special preempt_count accessors: - task_preempt_count() for when we're interested in the preemption count of another (non-running) task. - init_task_preempt_count() for properly initializing the preemption count. - init_idle_preempt_count() a special case of the above for the idle threads. With these no generic code ever touches thread_info::preempt_count anymore and architectures could choose to remove it. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-jf5swrio8l78j37d06fzmo4r@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* sched, arch: Create asm/preempt.hPeter Zijlstra2013-09-251-0/+54
In order to prepare to per-arch implementations of preempt_count move the required bits into an asm-generic header and use this for all archs. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/n/tip-h5j0c1r3e3fk015m30h8f1zx@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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