1. 22 Jul, 2011 2 commits
  2. 21 Jul, 2011 9 commits
  3. 20 Jul, 2011 20 commits
    • Linus Torvalds's avatar
      Merge branch 'core-urgent-for-linus' of... · cf6ace16
      Linus Torvalds authored
      Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
      
      * 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
        signal: align __lock_task_sighand() irq disabling and RCU
        softirq,rcu: Inform RCU of irq_exit() activity
        sched: Add irq_{enter,exit}() to scheduler_ipi()
        rcu: protect __rcu_read_unlock() against scheduler-using irq handlers
        rcu: Streamline code produced by __rcu_read_unlock()
        rcu: Fix RCU_BOOST race handling current->rcu_read_unlock_special
        rcu: decrease rcu_report_exp_rnp coupling with scheduler
      cf6ace16
    • Linus Torvalds's avatar
      Merge branch 'sched-urgent-for-linus' of... · acc11eab
      Linus Torvalds authored
      Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
      
      * 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
        sched: Avoid creating superfluous NUMA domains on non-NUMA systems
        sched: Allow for overlapping sched_domain spans
        sched: Break out cpu_power from the sched_group structure
      acc11eab
    • Linus Torvalds's avatar
      Merge branch 'x86-urgent-for-linus' of... · 919d25a7
      Linus Torvalds authored
      Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip
      
      * 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
        x86. reboot: Make Dell Latitude E6320 use reboot=pci
        x86, doc only: Correct real-mode kernel header offset for init_size
        x86: Disable AMD_NUMA for 32bit for now
      919d25a7
    • Ingo Molnar's avatar
      Merge branch 'rcu/urgent' of... · d1e9ae47
      Ingo Molnar authored
      Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu into core/urgent
      d1e9ae47
    • Paul E. McKenney's avatar
      signal: align __lock_task_sighand() irq disabling and RCU · a841796f
      Paul E. McKenney authored
      The __lock_task_sighand() function calls rcu_read_lock() with interrupts
      and preemption enabled, but later calls rcu_read_unlock() with interrupts
      disabled.  It is therefore possible that this RCU read-side critical
      section will be preempted and later RCU priority boosted, which means that
      rcu_read_unlock() will call rt_mutex_unlock() in order to deboost itself, but
      with interrupts disabled. This results in lockdep splats, so this commit
      nests the RCU read-side critical section within the interrupt-disabled
      region of code.  This prevents the RCU read-side critical section from
      being preempted, and thus prevents the attempt to deboost with interrupts
      disabled.
      
      It is quite possible that a better long-term fix is to make rt_mutex_unlock()
      disable irqs when acquiring the rt_mutex structure's ->wait_lock.
      Signed-off-by: 's avatarPaul E. McKenney <paul.mckenney@linaro.org>
      Signed-off-by: 's avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      a841796f
    • Peter Zijlstra's avatar
      softirq,rcu: Inform RCU of irq_exit() activity · ec433f0c
      Peter Zijlstra authored
      The rcu_read_unlock_special() function relies on in_irq() to exclude
      scheduler activity from interrupt level.  This fails because exit_irq()
      can invoke the scheduler after clearing the preempt_count() bits that
      in_irq() uses to determine that it is at interrupt level.  This situation
      can result in failures as follows:
      
       $task			IRQ		SoftIRQ
      
       rcu_read_lock()
      
       /* do stuff */
      
       <preempt> |= UNLOCK_BLOCKED
      
       rcu_read_unlock()
         --t->rcu_read_lock_nesting
      
      			irq_enter();
      			/* do stuff, don't use RCU */
      			irq_exit();
      			  sub_preempt_count(IRQ_EXIT_OFFSET);
      			  invoke_softirq()
      
      					ttwu();
      					  spin_lock_irq(&pi->lock)
      					  rcu_read_lock();
      					  /* do stuff */
      					  rcu_read_unlock();
      					    rcu_read_unlock_special()
      					      rcu_report_exp_rnp()
      					        ttwu()
      					          spin_lock_irq(&pi->lock) /* deadlock */
      
         rcu_read_unlock_special(t);
      
      Ed can simply trigger this 'easy' because invoke_softirq() immediately
      does a ttwu() of ksoftirqd/# instead of doing the in-place softirq stuff
      first, but even without that the above happens.
      
      Cure this by also excluding softirqs from the
      rcu_read_unlock_special() handler and ensuring the force_irqthreads
      ksoftirqd/# wakeup is done from full softirq context.
      
      [ Alternatively, delaying the ->rcu_read_lock_nesting decrement
        until after the special handling would make the thing more robust
        in the face of interrupts as well.  And there is a separate patch
        for that. ]
      
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Reported-and-tested-by: 's avatarEd Tomlinson <edt@aei.ca>
      Signed-off-by: 's avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Signed-off-by: 's avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      ec433f0c
    • Peter Zijlstra's avatar
      sched: Add irq_{enter,exit}() to scheduler_ipi() · c5d753a5
      Peter Zijlstra authored
      Ensure scheduler_ipi() calls irq_{enter,exit} when it does some actual
      work. Traditionally we never did any actual work from the resched IPI
      and all magic happened in the return from interrupt path.
      
      Now that we do do some work, we need to ensure irq_{enter,exit} are
      called so that we don't confuse things.
      
      This affects things like timekeeping, NO_HZ and RCU, basically
      everything with a hook in irq_enter/exit.
      
      Explicit examples of things going wrong are:
      
        sched_clock_cpu() -- has a callback when leaving NO_HZ state to take
                          a new reading from GTOD and TSC. Without this
                          callback, time is stuck in the past.
      
        RCU -- needs in_irq() to work in order to avoid some nasty deadlocks
      Signed-off-by: 's avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Signed-off-by: 's avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      c5d753a5
    • Paul E. McKenney's avatar
      rcu: protect __rcu_read_unlock() against scheduler-using irq handlers · 10f39bb1
      Paul E. McKenney authored
      The addition of RCU read-side critical sections within runqueue and
      priority-inheritance lock critical sections introduced some deadlock
      cycles, for example, involving interrupts from __rcu_read_unlock()
      where the interrupt handlers call wake_up().  This situation can cause
      the instance of __rcu_read_unlock() invoked from interrupt to do some
      of the processing that would otherwise have been carried out by the
      task-level instance of __rcu_read_unlock().  When the interrupt-level
      instance of __rcu_read_unlock() is called with a scheduler lock held
      from interrupt-entry/exit situations where in_irq() returns false,
      deadlock can result.
      
      This commit resolves these deadlocks by using negative values of
      the per-task ->rcu_read_lock_nesting counter to indicate that an
      instance of __rcu_read_unlock() is in flight, which in turn prevents
      instances from interrupt handlers from doing any special processing.
      This patch is inspired by Steven Rostedt's earlier patch that similarly
      made __rcu_read_unlock() guard against interrupt-mediated recursion
      (see https://lkml.org/lkml/2011/7/15/326), but this commit refines
      Steven's approach to avoid the need for preemption disabling on the
      __rcu_read_unlock() fastpath and to also avoid the need for manipulating
      a separate per-CPU variable.
      
      This patch avoids need for preempt_disable() by instead using negative
      values of the per-task ->rcu_read_lock_nesting counter.  Note that nested
      rcu_read_lock()/rcu_read_unlock() pairs are still permitted, but they will
      never see ->rcu_read_lock_nesting go to zero, and will therefore never
      invoke rcu_read_unlock_special(), thus preventing them from seeing the
      RCU_READ_UNLOCK_BLOCKED bit should it be set in ->rcu_read_unlock_special.
      This patch also adds a check for ->rcu_read_unlock_special being negative
      in rcu_check_callbacks(), thus preventing the RCU_READ_UNLOCK_NEED_QS
      bit from being set should a scheduling-clock interrupt occur while
      __rcu_read_unlock() is exiting from an outermost RCU read-side critical
      section.
      
      Of course, __rcu_read_unlock() can be preempted during the time that
      ->rcu_read_lock_nesting is negative.  This could result in the setting
      of the RCU_READ_UNLOCK_BLOCKED bit after __rcu_read_unlock() checks it,
      and would also result it this task being queued on the corresponding
      rcu_node structure's blkd_tasks list.  Therefore, some later RCU read-side
      critical section would enter rcu_read_unlock_special() to clean up --
      which could result in deadlock if that critical section happened to be in
      the scheduler where the runqueue or priority-inheritance locks were held.
      
      This situation is dealt with by making rcu_preempt_note_context_switch()
      check for negative ->rcu_read_lock_nesting, thus refraining from
      queuing the task (and from setting RCU_READ_UNLOCK_BLOCKED) if we are
      already exiting from the outermost RCU read-side critical section (in
      other words, we really are no longer actually in that RCU read-side
      critical section).  In addition, rcu_preempt_note_context_switch()
      invokes rcu_read_unlock_special() to carry out the cleanup in this case,
      which clears out the ->rcu_read_unlock_special bits and dequeues the task
      (if necessary), in turn avoiding needless delay of the current RCU grace
      period and needless RCU priority boosting.
      
      It is still illegal to call rcu_read_unlock() while holding a scheduler
      lock if the prior RCU read-side critical section has ever had either
      preemption or irqs enabled.  However, the common use case is legal,
      namely where then entire RCU read-side critical section executes with
      irqs disabled, for example, when the scheduler lock is held across the
      entire lifetime of the RCU read-side critical section.
      Signed-off-by: 's avatarPaul E. McKenney <paul.mckenney@linaro.org>
      Signed-off-by: 's avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      10f39bb1
    • Peter Zijlstra's avatar
      sched: Avoid creating superfluous NUMA domains on non-NUMA systems · d110235d
      Peter Zijlstra authored
      When creating sched_domains, stop when we've covered the entire
      target span instead of continuing to create domains, only to
      later find they're redundant and throw them away again.
      
      This avoids single node systems from touching funny NUMA
      sched_domain creation code and reduces the risks of the new
      SD_OVERLAP code.
      Requested-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: 's avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Anton Blanchard <anton@samba.org>
      Cc: mahesh@linux.vnet.ibm.com
      Cc: benh@kernel.crashing.org
      Cc: linuxppc-dev@lists.ozlabs.org
      Link: http://lkml.kernel.org/r/1311180177.29152.57.camel@twinsSigned-off-by: 's avatarIngo Molnar <mingo@elte.hu>
      d110235d
    • Peter Zijlstra's avatar
      sched: Allow for overlapping sched_domain spans · e3589f6c
      Peter Zijlstra authored
      Allow for sched_domain spans that overlap by giving such domains their
      own sched_group list instead of sharing the sched_groups amongst
      each-other.
      
      This is needed for machines with more than 16 nodes, because
      sched_domain_node_span() will generate a node mask from the
      16 nearest nodes without regard if these masks have any overlap.
      
      Currently sched_domains have a sched_group that maps to their child
      sched_domain span, and since there is no overlap we share the
      sched_group between the sched_domains of the various CPUs. If however
      there is overlap, we would need to link the sched_group list in
      different ways for each cpu, and hence sharing isn't possible.
      
      In order to solve this, allocate private sched_groups for each CPU's
      sched_domain but have the sched_groups share a sched_group_power
      structure such that we can uniquely track the power.
      Reported-and-tested-by: 's avatarAnton Blanchard <anton@samba.org>
      Signed-off-by: 's avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Link: http://lkml.kernel.org/n/tip-08bxqw9wis3qti9u5inifh3y@git.kernel.orgSigned-off-by: 's avatarIngo Molnar <mingo@elte.hu>
      e3589f6c
    • Peter Zijlstra's avatar
      sched: Break out cpu_power from the sched_group structure · 9c3f75cb
      Peter Zijlstra authored
      In order to prepare for non-unique sched_groups per domain, we need to
      carry the cpu_power elsewhere, so put a level of indirection in.
      Reported-and-tested-by: 's avatarAnton Blanchard <anton@samba.org>
      Signed-off-by: 's avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Link: http://lkml.kernel.org/n/tip-qkho2byuhe4482fuknss40ad@git.kernel.orgSigned-off-by: 's avatarIngo Molnar <mingo@elte.hu>
      9c3f75cb
    • Linus Torvalds's avatar
    • Linus Torvalds's avatar
      Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/linux-arm-soc · 47126d80
      Linus Torvalds authored
      * 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/linux-arm-soc:
        davinci: DM365 EVM: fix video input mux bits
        ARM: davinci: Check for NULL return from irq_alloc_generic_chip
        arm: davinci: Fix low level gpio irq handlers' argument
      47126d80
    • Shaohua Li's avatar
      vmscan: fix a livelock in kswapd · 4746efde
      Shaohua Li authored
      I'm running a workload which triggers a lot of swap in a machine with 4
      nodes.  After I kill the workload, I found a kswapd livelock.  Sometimes
      kswapd3 or kswapd2 are keeping running and I can't access filesystem,
      but most memory is free.
      
      This looks like a regression since commit 08951e54 ("mm: vmscan:
      correct check for kswapd sleeping in sleeping_prematurely").
      
      Node 2 and 3 have only ZONE_NORMAL, but balance_pgdat() will return 0
      for classzone_idx.  The reason is end_zone in balance_pgdat() is 0 by
      default, if all zones have watermark ok, end_zone will keep 0.
      
      Later sleeping_prematurely() always returns true.  Because this is an
      order 3 wakeup, and if classzone_idx is 0, both balanced_pages and
      present_pages in pgdat_balanced() are 0.  We add a special case here.
      If a zone has no page, we think it's balanced.  This fixes the livelock.
      Signed-off-by: 's avatarShaohua Li <shaohua.li@intel.com>
      Acked-by: 's avatarMel Gorman <mgorman@suse.de>
      Cc: Minchan Kim <minchan.kim@gmail.com>
      Cc: <stable@kernel.org>
      Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
      4746efde
    • Akinobu Mita's avatar
      fs/libfs.c: fix simple_attr_write() on 32bit machines · f7b88631
      Akinobu Mita authored
      Assume that /sys/kernel/debug/dummy64 is debugfs file created by
      debugfs_create_x64().
      
      	# cd /sys/kernel/debug
      	# echo 0x1234567812345678 > dummy64
      	# cat dummy64
      	0x0000000012345678
      
      	# echo 0x80000000 > dummy64
      	# cat dummy64
      	0xffffffff80000000
      
      A value larger than INT_MAX cannot be written to the debugfs file created
      by debugfs_create_u64 or debugfs_create_x64 on 32bit machine.  Because
      simple_attr_write() uses simple_strtol() for the conversion.
      
      To fix this, use simple_strtoll() instead.
      Signed-off-by: 's avatarAkinobu Mita <akinobu.mita@gmail.com>
      Cc: Greg Kroah-Hartman <gregkh@suse.de>
      Signed-off-by: 's avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
      f7b88631
    • Linus Torvalds's avatar
      Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6 · e501f29c
      Linus Torvalds authored
      * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs-2.6:
        vfs: fix race in rcu lookup of pruned dentry
        Fix cifs_get_root()
      
      [ Edited the last commit to get rid of a 'unused variable "seq"'
        warning due to Al editing the patch.  - Linus ]
      e501f29c
    • Linus Torvalds's avatar
      vfs: fix race in rcu lookup of pruned dentry · 59430262
      Linus Torvalds authored
      Don't update *inode in __follow_mount_rcu() until we'd verified that
      there is mountpoint there.  Kudos to Hugh Dickins for catching that
      one in the first place and eventually figuring out the solution (and
      catching a braino in the earlier version of patch).
      Signed-off-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: 's avatarAl Viro <viro@zeniv.linux.org.uk>
      59430262
    • Paul E. McKenney's avatar
      rcu: Streamline code produced by __rcu_read_unlock() · be0e1e21
      Paul E. McKenney authored
      Given some common flag combinations, particularly -Os, gcc will inline
      rcu_read_unlock_special() despite its being in an unlikely() clause.
      Use noinline to prohibit this misoptimization.
      
      In addition, move the second barrier() in __rcu_read_unlock() so that
      it is not on the common-case code path.  This will allow the compiler to
      generate better code for the common-case path through __rcu_read_unlock().
      Suggested-by: 's avatarLinus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: 's avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      Acked-by: 's avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
      be0e1e21
    • Paul E. McKenney's avatar
      rcu: Fix RCU_BOOST race handling current->rcu_read_unlock_special · 7765be2f
      Paul E. McKenney authored
      The RCU_BOOST commits for TREE_PREEMPT_RCU introduced an other-task
      write to a new RCU_READ_UNLOCK_BOOSTED bit in the task_struct structure's
      ->rcu_read_unlock_special field, but, as noted by Steven Rostedt, without
      correctly synchronizing all accesses to ->rcu_read_unlock_special.
      This could result in bits in ->rcu_read_unlock_special being spuriously
      set and cleared due to conflicting accesses, which in turn could result
      in deadlocks between the rcu_node structure's ->lock and the scheduler's
      rq and pi locks.  These deadlocks would result from RCU incorrectly
      believing that the just-ended RCU read-side critical section had been
      preempted and/or boosted.  If that RCU read-side critical section was
      executed with either rq or pi locks held, RCU's ensuing (incorrect)
      calls to the scheduler would cause the scheduler to attempt to once
      again acquire the rq and pi locks, resulting in deadlock.  More complex
      deadlock cycles are also possible, involving multiple rq and pi locks
      as well as locks from multiple rcu_node structures.
      
      This commit fixes synchronization by creating ->rcu_boosted field in
      task_struct that is accessed and modified only when holding the ->lock
      in the rcu_node structure on which the task is queued (on that rcu_node
      structure's ->blkd_tasks list).  This results in tasks accessing only
      their own current->rcu_read_unlock_special fields, making unsynchronized
      access once again legal, and keeping the rcu_read_unlock() fastpath free
      of atomic instructions and memory barriers.
      
      The reason that the rcu_read_unlock() fastpath does not need to access
      the new current->rcu_boosted field is that this new field cannot
      be non-zero unless the RCU_READ_UNLOCK_BLOCKED bit is set in the
      current->rcu_read_unlock_special field.  Therefore, rcu_read_unlock()
      need only test current->rcu_read_unlock_special: if that is zero, then
      current->rcu_boosted must also be zero.
      
      This bug does not affect TINY_PREEMPT_RCU because this implementation
      of RCU accesses current->rcu_read_unlock_special with irqs disabled,
      thus preventing races on the !SMP systems that TINY_PREEMPT_RCU runs on.
      Maybe-reported-by: 's avatarDave Jones <davej@redhat.com>
      Maybe-reported-by: 's avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
      Reported-by: 's avatarSteven Rostedt <rostedt@goodmis.org>
      Signed-off-by: 's avatarPaul E. McKenney <paul.mckenney@linaro.org>
      Signed-off-by: 's avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      Reviewed-by: 's avatarSteven Rostedt <rostedt@goodmis.org>
      7765be2f
    • Paul E. McKenney's avatar
      rcu: decrease rcu_report_exp_rnp coupling with scheduler · 131906b0
      Paul E. McKenney authored
      PREEMPT_RCU read-side critical sections blocking an expedited grace
      period invoke rcu_report_exp_rnp().  When the last such critical section
      has completed, rcu_report_exp_rnp() invokes the scheduler to wake up the
      task that invoked synchronize_rcu_expedited() -- needlessly holding the
      root rcu_node structure's lock while doing so, thus needlessly providing
      a way for RCU and the scheduler to deadlock.
      
      This commit therefore releases the root rcu_node structure's lock before
      calling wake_up().
      Reported-by: 's avatarEd Tomlinson <edt@aei.ca>
      Signed-off-by: 's avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      131906b0
  4. 19 Jul, 2011 3 commits
  5. 18 Jul, 2011 6 commits