linux-toradex.git/include/linux/sched.h, branch v3.19-rc5

syscalls: implement execveat() system call

2014-12-13T20:42:51+00:00

This patchset adds execveat(2) for x86, and is derived from Meredydd
Luff's patch from Sept 2012 (https://lkml.org/lkml/2012/9/11/528).

The primary aim of adding an execveat syscall is to allow an
implementation of fexecve(3) that does not rely on the /proc filesystem,
at least for executables (rather than scripts).  The current glibc version
of fexecve(3) is implemented via /proc, which causes problems in sandboxed
or otherwise restricted environments.

Given the desire for a /proc-free fexecve() implementation, HPA suggested
(https://lkml.org/lkml/2006/7/11/556) that an execveat(2) syscall would be
an appropriate generalization.

Also, having a new syscall means that it can take a flags argument without
back-compatibility concerns.  The current implementation just defines the
AT_EMPTY_PATH and AT_SYMLINK_NOFOLLOW flags, but other flags could be
added in future -- for example, flags for new namespaces (as suggested at
https://lkml.org/lkml/2006/7/11/474).

Related history:
 - https://lkml.org/lkml/2006/12/27/123 is an example of someone
   realizing that fexecve() is likely to fail in a chroot environment.
 - http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=514043 covered
   documenting the /proc requirement of fexecve(3) in its manpage, to
   "prevent other people from wasting their time".
 - https://bugzilla.redhat.com/show_bug.cgi?id=241609 described a
   problem where a process that did setuid() could not fexecve()
   because it no longer had access to /proc/self/fd; this has since
   been fixed.

This patch (of 4):

Add a new execveat(2) system call.  execveat() is to execve() as openat()
is to open(): it takes a file descriptor that refers to a directory, and
resolves the filename relative to that.

In addition, if the filename is empty and AT_EMPTY_PATH is specified,
execveat() executes the file to which the file descriptor refers.  This
replicates the functionality of fexecve(), which is a system call in other
UNIXen, but in Linux glibc it depends on opening "/proc/self/fd/" (and
so relies on /proc being mounted).

The filename fed to the executed program as argv[0] (or the name of the
script fed to a script interpreter) will be of the form "/dev/fd/"
(for an empty filename) or "/dev/fd//", effectively
reflecting how the executable was found.  This does however mean that
execution of a script in a /proc-less environment won't work; also, script
execution via an O_CLOEXEC file descriptor fails (as the file will not be
accessible after exec).

Based on patches by Meredydd Luff.

Signed-off-by: David Drysdale 
Cc: Meredydd Luff 
Cc: Shuah Khan 
Cc: "Eric W. Biederman" 
Cc: Andy Lutomirski 
Cc: Alexander Viro 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: "H. Peter Anvin" 
Cc: Kees Cook 
Cc: Arnd Bergmann 
Cc: Rich Felker 
Cc: Christoph Hellwig 
Cc: Michael Kerrisk 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

memcg: turn memcg_kmem_skip_account into a bit field

2014-12-13T20:42:47+00:00

It isn't supposed to stack, so turn it into a bit-field to save 4 bytes on
the task_struct.

Also, remove the memcg_stop/resume_kmem_account helpers - it is clearer to
set/clear the flag inline.  Regarding the overwhelming comment to the
helpers, which is removed by this patch too, we already have a compact yet
accurate explanation in memcg_schedule_cache_create, no need in yet
another one.

Signed-off-by: Vladimir Davydov 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2014-12-10T05:21:34+00:00

Pull scheduler updates from Ingo Molnar:
 "The main changes in this cycle are:

   - 'Nested Sleep Debugging', activated when CONFIG_DEBUG_ATOMIC_SLEEP=y.

     This instruments might_sleep() checks to catch places that nest
     blocking primitives - such as mutex usage in a wait loop.  Such
     bugs can result in hard to debug races/hangs.

     Another category of invalid nesting that this facility will detect
     is the calling of blocking functions from within schedule() ->
     sched_submit_work() -> blk_schedule_flush_plug().

     There's some potential for false positives (if secondary blocking
     primitives themselves are not ready yet for this facility), but the
     kernel will warn once about such bugs per bootup, so the warning
     isn't much of a nuisance.

     This feature comes with a number of fixes, for problems uncovered
     with it, so no messages are expected normally.

   - Another round of sched/numa optimizations and refinements, for
     CONFIG_NUMA_BALANCING=y.

   - Another round of sched/dl fixes and refinements.

  Plus various smaller fixes and cleanups"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
  sched: Add missing rcu protection to wake_up_all_idle_cpus
  sched/deadline: Introduce start_hrtick_dl() for !CONFIG_SCHED_HRTICK
  sched/numa: Init numa balancing fields of init_task
  sched/deadline: Remove unnecessary definitions in cpudeadline.h
  sched/cpupri: Remove unnecessary definitions in cpupri.h
  sched/deadline: Fix rq->dl.pushable_tasks bug in push_dl_task()
  sched/fair: Fix stale overloaded status in the busiest group finding logic
  sched: Move p->nr_cpus_allowed check to select_task_rq()
  sched/completion: Document when to use wait_for_completion_io_*()
  sched: Update comments about CLONE_NEWUTS and CLONE_NEWIPC
  sched/fair: Kill task_struct::numa_entry and numa_group::task_list
  sched: Refactor task_struct to use numa_faults instead of numa_* pointers
  sched/deadline: Don't check CONFIG_SMP in switched_from_dl()
  sched/deadline: Reschedule from switched_from_dl() after a successful pull
  sched/deadline: Push task away if the deadline is equal to curr during wakeup
  sched/deadline: Add deadline rq status print
  sched/deadline: Fix artificial overrun introduced by yield_task_dl()
  sched/rt: Clean up check_preempt_equal_prio()
  sched/core: Use dl_bw_of() under rcu_read_lock_sched()
  sched: Check if we got a shallowest_idle_cpu before searching for least_loaded_cpu
  ...

sched: Refactor task_struct to use numa_faults instead of numa_* pointers

2014-11-04T06:17:57+00:00

This patch simplifies task_struct by removing the four numa_* pointers
in the same array and replacing them with the array pointer. By doing this,
on x86_64, the size of task_struct is reduced by 3 ulong pointers (24 bytes on
x86_64).

A new parameter is added to the task_faults_idx function so that it can return
an index to the correct offset, corresponding with the old precalculated
pointers.

All of the code in sched/ that depended on task_faults_idx and numa_* was
changed in order to match the new logic.

Signed-off-by: Iulia Manda 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: mgorman@suse.de
Cc: dave@stgolabs.net
Cc: riel@redhat.com
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/20141031001331.GA30662@winterfell
Signed-off-by: Ingo Molnar

rcu: Remove redundant TREE_PREEMPT_RCU config option

2014-10-29T17:20:05+00:00

PREEMPT_RCU and TREE_PREEMPT_RCU serve the same function after
TINY_PREEMPT_RCU has been removed. This patch removes TREE_PREEMPT_RCU
and uses PREEMPT_RCU config option in its place.

Signed-off-by: Pranith Kumar 
Signed-off-by: Paul E. McKenney

sched: Exclude cond_resched() from nested sleep test

2014-10-28T09:56:57+00:00

cond_resched() is a preemption point, not strictly a blocking
primitive, so exclude it from the ->state test.

In particular, preemption preserves task_struct::state.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: tglx@linutronix.de
Cc: ilya.dryomov@inktank.com
Cc: umgwanakikbuti@gmail.com
Cc: oleg@redhat.com
Cc: Alex Elder 
Cc: Andrew Morton 
Cc: Axel Lin 
Cc: Daniel Borkmann 
Cc: Dave Jones 
Cc: Jason Baron 
Cc: Linus Torvalds 
Cc: Rusty Russell 
Cc: Steven Rostedt 
Link: http://lkml.kernel.org/r/20140924082242.656559952@infradead.org
Signed-off-by: Ingo Molnar

sched: Debug nested sleeps

2014-10-28T09:56:52+00:00

Validate we call might_sleep() with TASK_RUNNING, which catches places
where we nest blocking primitives, eg. mutex usage in a wait loop.

Since all blocking is arranged through task_struct::state, nesting
this will cause the inner primitive to set TASK_RUNNING and the outer
will thus not block.

Another observed problem is calling a blocking function from
schedule()->sched_submit_work()->blk_schedule_flush_plug() which will
then destroy the task state for the actual __schedule() call that
comes after it.

Signed-off-by: Peter Zijlstra (Intel) 
Cc: tglx@linutronix.de
Cc: ilya.dryomov@inktank.com
Cc: umgwanakikbuti@gmail.com
Cc: oleg@redhat.com
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/20140924082242.591637616@infradead.org
Signed-off-by: Ingo Molnar

sched/deadline: Ensure that updates to exclusive cpusets don't break AC

2014-10-28T09:48:00+00:00

How we deal with updates to exclusive cpusets is currently broken.
As an example, suppose we have an exclusive cpuset composed of
two cpus: A[cpu0,cpu1]. We can assign SCHED_DEADLINE task to it
up to the allowed bandwidth. If we want now to modify cpusetA's
cpumask, we have to check that removing a cpu's amount of
bandwidth doesn't break AC guarantees. This thing isn't checked
in the current code.

This patch fixes the problem above, denying an update if the
new cpumask won't have enough bandwidth for SCHED_DEADLINE tasks
that are currently active.

Signed-off-by: Juri Lelli 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Linus Torvalds 
Cc: Li Zefan 
Cc: cgroups@vger.kernel.org
Link: http://lkml.kernel.org/r/5433E6AF.5080105@arm.com
Signed-off-by: Ingo Molnar

sched/deadline: Fix bandwidth check/update when migrating tasks between exclusive cpusets

2014-10-28T09:47:58+00:00

Exclusive cpusets are the only way users can restrict SCHED_DEADLINE tasks
affinity (performing what is commonly called clustered scheduling).
Unfortunately, such thing is currently broken for two reasons:

 - No check is performed when the user tries to attach a task to
   an exlusive cpuset (recall that exclusive cpusets have an
   associated maximum allowed bandwidth).

 - Bandwidths of source and destination cpusets are not correctly
   updated after a task is migrated between them.

This patch fixes both things at once, as they are opposite faces
of the same coin.

The check is performed in cpuset_can_attach(), as there aren't any
points of failure after that function. The updated is split in two
halves. We first reserve bandwidth in the destination cpuset, after
we pass the check in cpuset_can_attach(). And we then release
bandwidth from the source cpuset when the task's affinity is
actually changed. Even if there can be time windows when sched_setattr()
may erroneously fail in the source cpuset, we are fine with it, as
we can't perfom an atomic update of both cpusets at once.

Reported-by: Daniel Wagner 
Reported-by: Vincent Legout 
Signed-off-by: Juri Lelli 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Dario Faggioli 
Cc: Michael Trimarchi 
Cc: Fabio Checconi 
Cc: michael@amarulasolutions.com
Cc: luca.abeni@unitn.it
Cc: Li Zefan 
Cc: Linus Torvalds 
Cc: cgroups@vger.kernel.org
Link: http://lkml.kernel.org/r/1411118561-26323-3-git-send-email-juri.lelli@arm.com
Signed-off-by: Ingo Molnar

Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2014-10-13T14:23:15+00:00

Pull scheduler updates from Ingo Molnar:
 "The main changes in this cycle were:

   - Optimized support for Intel "Cluster-on-Die" (CoD) topologies (Dave
     Hansen)

   - Various sched/idle refinements for better idle handling (Nicolas
     Pitre, Daniel Lezcano, Chuansheng Liu, Vincent Guittot)

   - sched/numa updates and optimizations (Rik van Riel)

   - sysbench speedup (Vincent Guittot)

   - capacity calculation cleanups/refactoring (Vincent Guittot)

   - Various cleanups to thread group iteration (Oleg Nesterov)

   - Double-rq-lock removal optimization and various refactorings
     (Kirill Tkhai)

   - various sched/deadline fixes

  ... and lots of other changes"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (72 commits)
  sched/dl: Use dl_bw_of() under rcu_read_lock_sched()
  sched/fair: Delete resched_cpu() from idle_balance()
  sched, time: Fix build error with 64 bit cputime_t on 32 bit systems
  sched: Improve sysbench performance by fixing spurious active migration
  sched/x86: Fix up typo in topology detection
  x86, sched: Add new topology for multi-NUMA-node CPUs
  sched/rt: Use resched_curr() in task_tick_rt()
  sched: Use rq->rd in sched_setaffinity() under RCU read lock
  sched: cleanup: Rename 'out_unlock' to 'out_free_new_mask'
  sched: Use dl_bw_of() under RCU read lock
  sched/fair: Remove duplicate code from can_migrate_task()
  sched, mips, ia64: Remove __ARCH_WANT_UNLOCKED_CTXSW
  sched: print_rq(): Don't use tasklist_lock
  sched: normalize_rt_tasks(): Don't use _irqsave for tasklist_lock, use task_rq_lock()
  sched: Fix the task-group check in tg_has_rt_tasks()
  sched/fair: Leverage the idle state info when choosing the "idlest" cpu
  sched: Let the scheduler see CPU idle states
  sched/deadline: Fix inter- exclusive cpusets migrations
  sched/deadline: Clear dl_entity params when setscheduling to different class
  sched/numa: Kill the wrong/dead TASK_DEAD check in task_numa_fault()
  ...