user/sven/linux.git/kernel/context_tracking.c, branch v4.2.4

context_tracking: Inherit TIF_NOHZ through forks instead of context switches

2015-05-07T10:02:51Z

TIF_NOHZ is used by context_tracking to force syscall slow-path on every task in order to track userspace roundtrips. As such, it must be set on all running tasks. It's currently explicitly inherited through context switches. There is no need to do it in this fast-path though. The flag could simply be set once for all on all tasks, whether they are running or not. Lets do this by setting the flag for the init task on early boot, and let it propagate through fork inheritance. While at it, mark context_tracking_cpu_set() as init code, we only need it at early boot time. Suggested-by: Oleg Nesterov Signed-off-by: Frederic Weisbecker Reviewed-by: Rik van Riel Cc: Borislav Petkov Cc: Chris Metcalf Cc: Dave Jones Cc: H. Peter Anvin Cc: Martin Schwidefsky Cc: Mike Galbraith Cc: Paul E . McKenney Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rafael J . Wysocki Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1430928266-24888-3-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar

context_tracking: Protect against recursion

2015-05-07T10:02:50Z

Context tracking recursion can happen when an exception triggers in the middle of a call to a context tracking probe. This special case can be caused by vmalloc faults. If an access to a memory area allocated by vmalloc happens in the middle of context_tracking_enter(), we may run into an endless fault loop because the exception in turn calls context_tracking_enter() which faults on the same vmalloc'ed memory, triggering an exception again, etc... Some rare crashes have been reported so lets protect against this with a recursion counter. Reported-by: Dave Jones Signed-off-by: Frederic Weisbecker Reviewed-by: Rik van Riel Acked-by: Peter Zijlstra (Intel) Cc: Borislav Petkov Cc: Chris Metcalf Cc: H. Peter Anvin Cc: Martin Schwidefsky Cc: Mike Galbraith Cc: Oleg Nesterov Cc: Paul E. McKenney Cc: Rafael J . Wysocki Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1430928266-24888-2-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar

context_tracking: Export context_tracking_user_enter/exit

2015-03-09T14:43:00Z

Export context_tracking_user_enter/exit so it can be used by KVM. Reviewed-by: Paul E. McKenney Signed-off-by: Rik van Riel Cc: Paul E. McKenney Cc: Andy Lutomirski Cc: Will deacon Cc: Marcelo Tosatti Cc: Christian Borntraeger Cc: Luiz Capitulino Cc: Paolo Bonzini Signed-off-by: Frederic Weisbecker

context_tracking: Run vtime_user_enter/exit only when state == CONTEXT_USER

2015-03-09T14:42:57Z

Only run vtime_user_enter, vtime_user_exit, and the user enter & exit trace points when we are entering or exiting user state, respectively. The KVM code in guest_enter and guest_exit already take care of calling vtime_guest_enter and vtime_guest_exit, respectively. The RCU code only distinguishes between "idle" and "not idle or kernel". There should be no need to add an additional (unused) state there. Reviewed-by: Paul E. McKenney Signed-off-by: Rik van Riel Cc: Paul E. McKenney Cc: Andy Lutomirski Cc: Will deacon Cc: Marcelo Tosatti Cc: Christian Borntraeger Cc: Luiz Capitulino Cc: Paolo Bonzini Signed-off-by: Frederic Weisbecker

context_tracking: Generalize context tracking APIs to support user and guest

2015-03-09T14:42:52Z

Generalize the context tracking APIs to support various nature of contexts. This is performed by splitting out the mechanism from context_tracking_user_enter and context_tracking_user_exit into context_tracking_enter and context_tracking_exit. The nature of the context we track is now detailed in a ctx_state parameter pushed to these APIs, allowing the same functions to not just track kernel <> user space switching, but also kernel <> guest transitions. But leave the old functions in order to avoid breaking ARM, which calls these functions from assembler code, and cannot easily use C enum parameters. Reviewed-by: Paul E. McKenney Signed-off-by: Rik van Riel Cc: Paul E. McKenney Cc: Andy Lutomirski Cc: Will deacon Cc: Marcelo Tosatti Cc: Christian Borntraeger Cc: Luiz Capitulino Cc: Paolo Bonzini Signed-off-by: Frederic Weisbecker

context_tracking: Rename context symbols to prepare for transition state

2015-03-09T14:42:50Z

Current context tracking symbols are designed to express living state. As such they are prefixed with "IN_": IN_USER, IN_KERNEL. Now we are going to use these symbols to also express state transitions such as context_tracking_enter(IN_USER) or context_tracking_exit(IN_USER). But while the "IN_" prefix works well to express entering a context, it's confusing to depict a context exit: context_tracking_exit(IN_USER) could mean two things: 1) We are exiting the current context to enter user context. 2) We are exiting the user context We want 2) but the reviewer may be confused and understand 1) So lets disambiguate these symbols and rename them to CONTEXT_USER and CONTEXT_KERNEL. Acked-by: Rik van Riel Cc: Paul E. McKenney Cc: Andy Lutomirski Cc: Will deacon Cc: Marcelo Tosatti Cc: Christian Borntraeger Cc: Luiz Capitulino Cc: Paolo Bonzini Signed-off-by: Frederic Weisbecker

sched: stop the unbound recursion in preempt_schedule_context()

2014-10-28T09:46:05Z

preempt_schedule_context() does preempt_enable_notrace() at the end and this can call the same function again; exception_exit() is heavy and it is quite possible that need-resched is true again. 1. Change this code to dec preempt_count() and check need_resched() by hand. 2. As Linus suggested, we can use the PREEMPT_ACTIVE bit and avoid the enable/disable dance around __schedule(). But in this case we need to move into sched/core.c. 3. Cosmetic, but x86 forgets to declare this function. This doesn't really matter because it is only called by asm helpers, still it make sense to add the declaration into asm/preempt.h to match preempt_schedule(). Reported-by: Sasha Levin Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Graf Cc: Andrew Morton Cc: Christoph Lameter Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Steven Rostedt Cc: Peter Anvin Cc: Andy Lutomirski Cc: Denys Vlasenko Cc: Chuck Ebbert Cc: Frederic Weisbecker Link: http://lkml.kernel.org/r/20141005202322.GB27962@redhat.com Signed-off-by: Ingo Molnar

x86/kprobes: Fix build errors and blacklist context_track_user

2014-06-14T07:07:44Z

This essentially reverts commit: ecd50f714c42 ("kprobes, x86: Call exception_enter after kprobes handled") since it causes build errors with CONFIG_CONTEXT_TRACKING and that has been made from misunderstandings; context_track_user_*() don't involve much in interrupt context, it just returns if in_interrupt() is true. Instead of changing the do_debug/int3(), this just adds context_track_user_*() to kprobes blacklist, since those are still can be called right before kprobes handles int3 and debug exceptions, and probing those will cause an infinite loop. Reported-by: Frederic Weisbecker Signed-off-by: Masami Hiramatsu Cc: Borislav Petkov Cc: Kees Cook Cc: Jiri Kosina Cc: Rusty Russell Cc: Steven Rostedt Cc: Seiji Aguchi Cc: Andrew Morton Cc: Kees Cook Link: http://lkml.kernel.org/r/20140614064711.7865.45957.stgit@kbuild-fedora.novalocal Signed-off-by: Ingo Molnar

asmlinkage: Add explicit __visible to drivers/, lib/, kernel/*

2014-05-05T23:07:46Z

As requested by Linus add explicit __visible to the asmlinkage users. This marks functions visible to assembler. Tree sweep for rest of tree. Signed-off-by: Andi Kleen Link: http://lkml.kernel.org/r/1398984278-29319-4-git-send-email-andi@firstfloor.org Signed-off-by: H. Peter Anvin

context_tracking: Wrap static key check into more intuitive function name

2013-12-02T19:43:14Z

Use a function with a meaningful name to check the global context tracking state. static_key_false() is a bit confusing for reviewers. Signed-off-by: Frederic Weisbecker Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Oleg Nesterov Cc: Steven Rostedt