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  1. 23 7月, 2015 1 次提交
  3. 23 6月, 2015 1 次提交
  5. 28 5月, 2015 3 次提交
  7. 16 1月, 2015 2 次提交
    • P
      rcu: Add GP-kthread-starvation checks to CPU stall warnings · fb81a44b
      由 Paul E. McKenney 提交于 
      This commit adds a message that is printed if the relevant grace-period
kthread has not been able to run for the two seconds preceding the
stall warning.  (The two seconds is double the maximum interval between
successive bouts of quiescent-state forcing.)
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      fb81a44b
    • P
      rcu: Make cond_resched_rcu_qs() apply to normal RCU flavors · 5cd37193
      由 Paul E. McKenney 提交于 
      Although cond_resched_rcu_qs() only applies to TASKS_RCU, it is used
in places where it would be useful for it to apply to the normal RCU
flavors, rcu_preempt, rcu_sched, and rcu_bh.  This is especially the
case for workloads that aggressively overload the system, particularly
those that generate large numbers of RCU updates on systems running
NO_HZ_FULL CPUs.  This commit therefore communicates quiescent states
from cond_resched_rcu_qs() to the normal RCU flavors.

Note that it is unfortunately necessary to leave the old ->passed_quiesce
mechanism in place to allow quiescent states that apply to only one
flavor to be recorded.  (Yes, we could decrement ->rcu_qs_ctr_snap in
that case, but that is not so good for debugging of RCU internals.)
In addition, if one of the RCU flavor's grace period has stalled, this
will invoke rcu_momentary_dyntick_idle(), resulting in a heavy-weight
quiescent state visible from other CPUs.
Reported-by: NSasha Levin <sasha.levin@oracle.com>
Reported-by: NDave Jones <davej@redhat.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Merge commit from Sasha Levin fixing a bug where __this_cpu()
  was used in preemptible code. ]
      5cd37193
  9. 07 1月, 2015 2 次提交
    • P
      rcu: Improve diagnostics for spurious RCU CPU stall warnings · 6ccd2ecd
      由 Paul E. McKenney 提交于 
      The current RCU CPU stall warning code will print "Stall ended before
state dump start" any time that the stall-warning code is triggered on
a CPU that has already reported a quiescent state for the current grace
period and if all quiescent states have been reported for the current
grace period.  However, a true stall can result in these symptoms, for
example, by preventing RCU's grace-period kthreads from ever running

This commit therefore checks for this condition, reporting the end of
the stall only if one of the grace-period counters has actually advanced.
Otherwise, it reports the last time that the grace-period kthread made
meaningful progress.  (In normal situations, the grace-period kthread
should make meaningful progress at least every jiffies_till_next_fqs
jiffies.)
Reported-by: NMiroslav Benes <mbenes@suse.cz>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: NMiroslav Benes <mbenes@suse.cz>
      6ccd2ecd
    • X
      documentation: Update sysfs path for rcu_cpu_stall_timeout · 84596ccb
      由 Xie XiuQi 提交于 
      Commit 6bfc09e2 ("rcu: Provide RCU CPU stall warnings for tiny RCU")
moved the rcu_cpu_stall_timeout module parameter from rcutree.c to
rcupdate.c, but failed to update Documentation/RCU/stallwarn.txt. This
commit therefore repairs this omission.

commit 96224daa ("documentation: Update sysfs path for rcu_cpu_stall_suppress")
updated the path for rcu_cpu_stall_suppress, but failed to update for
rcu_cpu_stall_timeout.
Signed-off-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      84596ccb
  11. 30 10月, 2014 1 次提交
  13. 29 10月, 2014 1 次提交
    • P
      rcu: Remove CONFIG_RCU_CPU_STALL_VERBOSE · 0eafa468
      由 Paul E. McKenney 提交于 
      The CONFIG_RCU_CPU_STALL_VERBOSE Kconfig parameter causes preemptible
RCU's CPU stall warnings to dump out any preempted tasks that are blocking
the current RCU grace period.  This information is useful, and the default
has been CONFIG_RCU_CPU_STALL_VERBOSE=y for some years.  It is therefore
time for this commit to remove this Kconfig parameter, so that future
kernel builds will always act as if CONFIG_RCU_CPU_STALL_VERBOSE=y.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      0eafa468
  15. 08 9月, 2014 1 次提交
  17. 07 8月, 2014 1 次提交
    • K
      list: fix order of arguments for hlist_add_after(_rcu) · 1d023284
      由 Ken Helias 提交于 
      All other add functions for lists have the new item as first argument
and the position where it is added as second argument.  This was changed
for no good reason in this function and makes using it unnecessary
confusing.

The name was changed to hlist_add_behind() to cause unconverted code to
generate a compile error instead of using the wrong parameter order.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NKen Helias <kenhelias@firemail.de>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>	[intel driver bits]
Cc: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      1d023284
  19. 08 7月, 2014 2 次提交
  21. 19 6月, 2014 1 次提交
  23. 29 4月, 2014 3 次提交
  25. 18 2月, 2014 2 次提交
  27. 11 2月, 2014 1 次提交
    • H
      Documentation/: update 00-INDEX files · 3cf8ca1c
      由 Henrik Austad 提交于 
      Some of the 00-INDEX files are somewhat outdated and some folders does
not contain 00-INDEX at all.  Only outdated (with the notably exception
of spi) indexes are touched here, the 169 folders without 00-INDEX has
not been touched.

New 00-INDEX
 - spi/* was added in a series of commits dating back to 2006

Added files (missing in (*/)00-INDEX)
 - dmatest.txt was added by commit 851b7e16 ("dmatest: run test via
   debugfs")
 - this_cpu_ops.txt was added by commit a1b2a555 ("percpu: add
   documentation on this_cpu operations")
 - ww-mutex-design.txt was added by commit 040a0a37 ("mutex: Add
   support for wound/wait style locks")
 - bcache.txt was added by commit cafe5635 ("bcache: A block layer
   cache")
 - kernel-per-CPU-kthreads.txt was added by commit 49717cb4
   ("kthread: Document ways of reducing OS jitter due to per-CPU
   kthreads")
 - phy.txt was added by commit ff764963 ("drivers: phy: add generic
   PHY framework")
 - block/null_blk was added by commit 12f8f4fc ("null_blk:
   documentation")
 - module-signing.txt was added by commit 3cafea30 ("Add
   Documentation/module-signing.txt file")
 - assoc_array.txt was added by commit 3cb98950 ("Add a generic
   associative array implementation.")
 - arm/IXP4xx was part of the initial repo
 - arm/cluster-pm-race-avoidance.txt was added by commit 7fe31d28
   ("ARM: mcpm: introduce helpers for platform coherency exit/setup")
 - arm/firmware.txt was added by commit 7366b92a ("ARM: Add
   interface for registering and calling firmware-specific operations")
 - arm/kernel_mode_neon.txt was added by commit 2afd0a05 ("ARM:
   7825/1: document the use of NEON in kernel mode")
 - arm/tcm.txt was added by commit bc581770 ("ARM: 5580/2: ARM TCM
   (Tightly-Coupled Memory) support v3")
 - arm/vlocks.txt was added by commit 9762f12d ("ARM: mcpm: Add
   baremetal voting mutexes")
 - blackfin/gptimers-example.c, Makefile was added by commit
   4b60779d ("Blackfin: add an example showing how to use the
   gptimers API")
 - devicetree/usage-model.txt was added by commit 31134efc ("dt:
   Linux DT usage model documentation")
 - fb/api.txt was added by commit fb21c2f4 ("fbdev: Add FOURCC-based
   format configuration API")
 - fb/sm501.txt was added by commit e6a04980 ("video, sm501: add
   edid and commandline support")
 - fb/udlfb.txt was added by commit 96f8d864 ("fbdev: move udlfb out
   of staging.")
 - filesystems/Makefile was added by commit 1e0051ae
   ("Documentation/fs/: split txt and source files")
 - filesystems/nfs/nfsd-admin-interfaces.txt was added by commit
   8a4c6e19 ("nfsd: document kernel interfaces for nfsd
   configuration")
 - ide/warm-plug-howto.txt was added by commit f74c9141 ("ide: add
   warm-plug support for IDE devices (take 2)")
 - laptops/Makefile was added by commit d49129ac
   ("Documentation/laptop/: split txt and source files")
 - leds/leds-blinkm.txt was added by commit b54cf35a ("LEDS: add
   BlinkM RGB LED driver, documentation and update MAINTAINERS")
 - leds/ledtrig-oneshot.txt was added by commit 5e417281 ("leds: add
   oneshot trigger")
 - leds/ledtrig-transient.txt was added by commit 44e1e9f8 ("leds:
   add new transient trigger for one shot timer activation")
 - m68k/README.buddha was part of the initial repo
 - networking/LICENSE.(qla3xxx|qlcnic|qlge) was added by commits
   40839129, c4e84bde, 5a4faa87
 - networking/Makefile was added by commit 3794f3e8 ("docsrc: build
   Documentation/ sources")
 - networking/i40evf.txt was added by commit 105bf2fe ("i40evf: add
   driver to kernel build system")
 - networking/ipsec.txt was added by commit b3c6efbc ("xfrm: Add
   file to document IPsec corner case")
 - networking/mac80211-auth-assoc-deauth.txt was added by commit
   3cd7920a ("mac80211: add auth/assoc/deauth flow diagram")
 - networking/netlink_mmap.txt was added by commit 5683264c
   ("netlink: add documentation for memory mapped I/O")
 - networking/nf_conntrack-sysctl.txt was added by commit c9f9e0e1
   ("netfilter: doc: add nf_conntrack sysctl api documentation") lan)
 - networking/team.txt was added by commit 3d249d4c ("net: introduce
   ethernet teaming device")
 - networking/vxlan.txt was added by commit d342894c ("vxlan:
   virtual extensible lan")
 - power/runtime_pm.txt was added by commit 5e928f77 ("PM: Introduce
   core framework for run-time PM of I/O devices (rev.  17)")
 - power/charger-manager.txt was added by commit 3bb3dbbd
   ("power_supply: Add initial Charger-Manager driver")
 - RCU/lockdep-splat.txt was added by commit d7bd2d68 ("rcu:
   Document interpretation of RCU-lockdep splats")
 - s390/kvm.txt was added by 5ecee4ba (KVM: s390: API documentation)
 - s390/qeth.txt was added by commit b4d72c08 ("qeth: bridgeport
   support - basic control")
 - scheduler/sched-bwc.txt was added by commit 88ebc08e ("sched: Add
   documentation for bandwidth control")
 - scsi/advansys.txt was added by commit 4bd6d7f3 ("[SCSI] advansys:
   Move documentation to Documentation/scsi")
 - scsi/bfa.txt was added by commit 1ec90174 ("[SCSI] bfa: add
   readme file")
 - scsi/bnx2fc.txt was added by commit 12b8fc10 ("[SCSI] bnx2fc: Add
   driver documentation")
 - scsi/cxgb3i.txt was added by commit c3673464 ("[SCSI] cxgb3i: Add
   cxgb3i iSCSI driver.")
 - scsi/hpsa.txt was added by commit 992ebcf1 ("[SCSI] hpsa: Add
   hpsa.txt to Documentation/scsi")
 - scsi/link_power_management_policy.txt was added by commit
   ca77329f ("[libata] Link power management infrastructure")
 - scsi/osd.txt was added by commit 78e0c621 ("[SCSI] osd:
   Documentation for OSD library")
 - scsi/scsi-parameter.txt was created/moved by commit 163475fb
   ("Documentation: move SCSI parameters to their own text file")
 - serial/driver was part of the initial repo
 - serial/n_gsm.txt was added by commit 323e8412 ("n_gsm: add a
   documentation")
 - timers/Makefile was added by commit 3794f3e8 ("docsrc: build
   Documentation/ sources")
 - virt/kvm/s390.txt was added by commit d9101fca ("KVM: s390:
   diagnose call documentation")
 - vm/split_page_table_lock was added by commit 49076ec2 ("mm:
   dynamically allocate page->ptl if it cannot be embedded to struct
   page")
 - w1/slaves/w1_ds28e04 was added by commit fbf7f7b4 ("w1: Add
   1-wire slave device driver for DS28E04-100")
 - w1/masters/omap-hdq was added by commit e0a29382 ("hdq:
   documentation for OMAP HDQ")
 - x86/early-microcode.txt was added by commit 0d91ea86 ("x86, doc:
   Documentation for early microcode loading")
 - x86/earlyprintk.txt was added by commit a1aade47 ("x86/doc:
   mini-howto for using earlyprintk=dbgp")
 - x86/entry_64.txt was added by commit 8b4777a4 ("x86-64: Document
   some of entry_64.S")
 - x86/pat.txt was added by commit d27554d8 ("x86: PAT
   documentation")

Moved files
 - arm/kernel_user_helpers.txt was moved out of arch/arm/kernel by
   commit 37b83046 ("ARM: kuser: move interface documentation out of
   the source code")
 - efi-stub.txt was moved out of x86/ and down into Documentation/ in
   commit 4172fe2f ("EFI stub documentation updates")
 - laptops/hpfall.c was moved out of hwmon/ and into laptops/ in commit
   efcfed9b ("Move hp_accel to drivers/platform/x86")
 - commit 5616c23a ("x86: doc: move x86-generic documentation from
   Doc/x86/i386"):
   * x86/usb-legacy-support.txt
   * x86/boot.txt
   * x86/zero_page.txt
 - power/video_extension.txt was moved to acpi in commit 70e66e4d
   ("ACPI / video: move video_extension.txt to Documentation/acpi")

Removed files (left in 00-INDEX)
 - memory.txt was removed by commit 00ea8990 ("memory.txt: remove
   stray information")
 - gpio.txt was moved to gpio/ in commit fd8e198c ("Documentation:
   gpiolib: document new interface")
 - networking/DLINK.txt was removed by commit 168e06ae
   ("drivers/net: delete old parallel port de600/de620 drivers")
 - serial/hayes-esp.txt was removed by commit f53a2ade ("tty: esp:
   remove broken driver")
 - s390/TAPE was removed by commit 9e280f66 ("[S390] remove tape
   block docu")
 - vm/locking was removed by commit 57ea8171 ("mm: documentation:
   remove hopelessly out-of-date locking doc")
 - laptops/acer-wmi.txt was remvoed by commit 02003667 ("acer-wmi:
   Delete out-of-date documentation")

Typos/misc issues
 - rpc-server-gss.txt was added as knfsd-rpcgss.txt in commit
   030d794b ("SUNRPC: Use gssproxy upcall for server RPCGSS
   authentication.")
 - commit b88cf73d ("net: add missing entries to
   Documentation/networking/00-INDEX")
   * generic-hdlc.txt was added as generic_hdlc.txt
   * spider_net.txt was added as spider-net.txt
 - w1/master/mxc-w1 was added as mxc_w1 by commit a5fd9139 ("w1: add
   1-wire master driver for i.MX27 / i.MX31")
 - s390/zfcpdump.txt was added as zfcpdump by commit 6920c12a
   ("[S390] Add Documentation/s390/00-INDEX.")
Signed-off-by: NHenrik Austad <henrik@austad.us>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>	[rcu bits]
Acked-by: NRob Landley <rob@landley.net>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Mark Brown <broonie@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Len Brown <len.brown@intel.com>
Cc: James Bottomley <JBottomley@parallels.com>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      3cf8ca1c
  29. 04 12月, 2013 2 次提交
    • P
      rcu: Break call_rcu() deadlock involving scheduler and perf · 96d3fd0d
      由 Paul E. McKenney 提交于 
      Dave Jones got the following lockdep splat:

>  ======================================================
>  [ INFO: possible circular locking dependency detected ]
>  3.12.0-rc3+ #92 Not tainted
>  -------------------------------------------------------
>  trinity-child2/15191 is trying to acquire lock:
>   (&rdp->nocb_wq){......}, at: [<ffffffff8108ff43>] __wake_up+0x23/0x50
>
> but task is already holding lock:
>   (&ctx->lock){-.-...}, at: [<ffffffff81154c19>] perf_event_exit_task+0x109/0x230
>
> which lock already depends on the new lock.
>
>
> the existing dependency chain (in reverse order) is:
>
> -> #3 (&ctx->lock){-.-...}:
>         [<ffffffff810cc243>] lock_acquire+0x93/0x200
>         [<ffffffff81733f90>] _raw_spin_lock+0x40/0x80
>         [<ffffffff811500ff>] __perf_event_task_sched_out+0x2df/0x5e0
>         [<ffffffff81091b83>] perf_event_task_sched_out+0x93/0xa0
>         [<ffffffff81732052>] __schedule+0x1d2/0xa20
>         [<ffffffff81732f30>] preempt_schedule_irq+0x50/0xb0
>         [<ffffffff817352b6>] retint_kernel+0x26/0x30
>         [<ffffffff813eed04>] tty_flip_buffer_push+0x34/0x50
>         [<ffffffff813f0504>] pty_write+0x54/0x60
>         [<ffffffff813e900d>] n_tty_write+0x32d/0x4e0
>         [<ffffffff813e5838>] tty_write+0x158/0x2d0
>         [<ffffffff811c4850>] vfs_write+0xc0/0x1f0
>         [<ffffffff811c52cc>] SyS_write+0x4c/0xa0
>         [<ffffffff8173d4e4>] tracesys+0xdd/0xe2
>
> -> #2 (&rq->lock){-.-.-.}:
>         [<ffffffff810cc243>] lock_acquire+0x93/0x200
>         [<ffffffff81733f90>] _raw_spin_lock+0x40/0x80
>         [<ffffffff810980b2>] wake_up_new_task+0xc2/0x2e0
>         [<ffffffff81054336>] do_fork+0x126/0x460
>         [<ffffffff81054696>] kernel_thread+0x26/0x30
>         [<ffffffff8171ff93>] rest_init+0x23/0x140
>         [<ffffffff81ee1e4b>] start_kernel+0x3f6/0x403
>         [<ffffffff81ee1571>] x86_64_start_reservations+0x2a/0x2c
>         [<ffffffff81ee1664>] x86_64_start_kernel+0xf1/0xf4
>
> -> #1 (&p->pi_lock){-.-.-.}:
>         [<ffffffff810cc243>] lock_acquire+0x93/0x200
>         [<ffffffff8173419b>] _raw_spin_lock_irqsave+0x4b/0x90
>         [<ffffffff810979d1>] try_to_wake_up+0x31/0x350
>         [<ffffffff81097d62>] default_wake_function+0x12/0x20
>         [<ffffffff81084af8>] autoremove_wake_function+0x18/0x40
>         [<ffffffff8108ea38>] __wake_up_common+0x58/0x90
>         [<ffffffff8108ff59>] __wake_up+0x39/0x50
>         [<ffffffff8110d4f8>] __call_rcu_nocb_enqueue+0xa8/0xc0
>         [<ffffffff81111450>] __call_rcu+0x140/0x820
>         [<ffffffff81111b8d>] call_rcu+0x1d/0x20
>         [<ffffffff81093697>] cpu_attach_domain+0x287/0x360
>         [<ffffffff81099d7e>] build_sched_domains+0xe5e/0x10a0
>         [<ffffffff81efa7fc>] sched_init_smp+0x3b7/0x47a
>         [<ffffffff81ee1f4e>] kernel_init_freeable+0xf6/0x202
>         [<ffffffff817200be>] kernel_init+0xe/0x190
>         [<ffffffff8173d22c>] ret_from_fork+0x7c/0xb0
>
> -> #0 (&rdp->nocb_wq){......}:
>         [<ffffffff810cb7ca>] __lock_acquire+0x191a/0x1be0
>         [<ffffffff810cc243>] lock_acquire+0x93/0x200
>         [<ffffffff8173419b>] _raw_spin_lock_irqsave+0x4b/0x90
>         [<ffffffff8108ff43>] __wake_up+0x23/0x50
>         [<ffffffff8110d4f8>] __call_rcu_nocb_enqueue+0xa8/0xc0
>         [<ffffffff81111450>] __call_rcu+0x140/0x820
>         [<ffffffff81111bb0>] kfree_call_rcu+0x20/0x30
>         [<ffffffff81149abf>] put_ctx+0x4f/0x70
>         [<ffffffff81154c3e>] perf_event_exit_task+0x12e/0x230
>         [<ffffffff81056b8d>] do_exit+0x30d/0xcc0
>         [<ffffffff8105893c>] do_group_exit+0x4c/0xc0
>         [<ffffffff810589c4>] SyS_exit_group+0x14/0x20
>         [<ffffffff8173d4e4>] tracesys+0xdd/0xe2
>
> other info that might help us debug this:
>
> Chain exists of:
>   &rdp->nocb_wq --> &rq->lock --> &ctx->lock
>
>   Possible unsafe locking scenario:
>
>         CPU0                    CPU1
>         ----                    ----
>    lock(&ctx->lock);
>                                 lock(&rq->lock);
>                                 lock(&ctx->lock);
>    lock(&rdp->nocb_wq);
>
>  *** DEADLOCK ***
>
> 1 lock held by trinity-child2/15191:
>  #0:  (&ctx->lock){-.-...}, at: [<ffffffff81154c19>] perf_event_exit_task+0x109/0x230
>
> stack backtrace:
> CPU: 2 PID: 15191 Comm: trinity-child2 Not tainted 3.12.0-rc3+ #92
>  ffffffff82565b70 ffff880070c2dbf8 ffffffff8172a363 ffffffff824edf40
>  ffff880070c2dc38 ffffffff81726741 ffff880070c2dc90 ffff88022383b1c0
>  ffff88022383aac0 0000000000000000 ffff88022383b188 ffff88022383b1c0
> Call Trace:
>  [<ffffffff8172a363>] dump_stack+0x4e/0x82
>  [<ffffffff81726741>] print_circular_bug+0x200/0x20f
>  [<ffffffff810cb7ca>] __lock_acquire+0x191a/0x1be0
>  [<ffffffff810c6439>] ? get_lock_stats+0x19/0x60
>  [<ffffffff8100b2f4>] ? native_sched_clock+0x24/0x80
>  [<ffffffff810cc243>] lock_acquire+0x93/0x200
>  [<ffffffff8108ff43>] ? __wake_up+0x23/0x50
>  [<ffffffff8173419b>] _raw_spin_lock_irqsave+0x4b/0x90
>  [<ffffffff8108ff43>] ? __wake_up+0x23/0x50
>  [<ffffffff8108ff43>] __wake_up+0x23/0x50
>  [<ffffffff8110d4f8>] __call_rcu_nocb_enqueue+0xa8/0xc0
>  [<ffffffff81111450>] __call_rcu+0x140/0x820
>  [<ffffffff8109bc8f>] ? local_clock+0x3f/0x50
>  [<ffffffff81111bb0>] kfree_call_rcu+0x20/0x30
>  [<ffffffff81149abf>] put_ctx+0x4f/0x70
>  [<ffffffff81154c3e>] perf_event_exit_task+0x12e/0x230
>  [<ffffffff81056b8d>] do_exit+0x30d/0xcc0
>  [<ffffffff810c9af5>] ? trace_hardirqs_on_caller+0x115/0x1e0
>  [<ffffffff810c9bcd>] ? trace_hardirqs_on+0xd/0x10
>  [<ffffffff8105893c>] do_group_exit+0x4c/0xc0
>  [<ffffffff810589c4>] SyS_exit_group+0x14/0x20
>  [<ffffffff8173d4e4>] tracesys+0xdd/0xe2

The underlying problem is that perf is invoking call_rcu() with the
scheduler locks held, but in NOCB mode, call_rcu() will with high
probability invoke the scheduler -- which just might want to use its
locks.  The reason that call_rcu() needs to invoke the scheduler is
to wake up the corresponding rcuo callback-offload kthread, which
does the job of starting up a grace period and invoking the callbacks
afterwards.

One solution (championed on a related problem by Lai Jiangshan) is to
simply defer the wakeup to some point where scheduler locks are no longer
held.  Since we don't want to unnecessarily incur the cost of such
deferral, the task before us is threefold:

1.	Determine when it is likely that a relevant scheduler lock is held.

2.	Defer the wakeup in such cases.

3.	Ensure that all deferred wakeups eventually happen, preferably
	sooner rather than later.

We use irqs_disabled_flags() as a proxy for relevant scheduler locks
being held.  This works because the relevant locks are always acquired
with interrupts disabled.  We may defer more often than needed, but that
is at least safe.

The wakeup deferral is tracked via a new field in the per-CPU and
per-RCU-flavor rcu_data structure, namely ->nocb_defer_wakeup.

This flag is checked by the RCU core processing.  The __rcu_pending()
function now checks this flag, which causes rcu_check_callbacks()
to initiate RCU core processing at each scheduling-clock interrupt
where this flag is set.  Of course this is not sufficient because
scheduling-clock interrupts are often turned off (the things we used to
be able to count on!).  So the flags are also checked on entry to any
state that RCU considers to be idle, which includes both NO_HZ_IDLE idle
state and NO_HZ_FULL user-mode-execution state.

This approach should allow call_rcu() to be invoked regardless of what
locks you might be holding, the key word being "should".
Reported-by: NDave Jones <davej@redhat.com>
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
      96d3fd0d
    • P
      rcu: Fix typo in Documentation/RCU/trace.txt · c9592ecb
      由 Paul E. McKenney 提交于 
      Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      c9592ecb
  31. 26 9月, 2013 1 次提交
  33. 25 9月, 2013 1 次提交
  35. 21 8月, 2013 1 次提交
    • P
      rcu: Increase rcutorture test coverage · 2ec1f2d9
      由 Paul E. McKenney 提交于 
      Currently, rcutorture has separate torture_types to test synchronous,
asynchronous, and expedited grace-period primitives.  This has
two disadvantages: (1) Three times the number of runs to cover the
combinations and (2) Little testing of concurrent combinations of the
three options.  This commit therefore adds a pair of module parameters
that control normal and expedited state, with the default being both
types, randomly selected, by the fakewriter processes, thus reducing
source-code size and increasing test coverage.  In addtion, the writer
task switches between asynchronous-normal and expedited grace-period
primitives driven by the same pair of module parameters.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
      2ec1f2d9
  37. 20 8月, 2013 1 次提交
    • P
      rcu: Update RTFP documentation · 6ae37718
      由 Paul E. McKenney 提交于 
      Note that this commit also updates the formatting of serveral of the
bibtex entries to conform to that of my .bib files.  I started
accumulating entries back in the 1980s, back when bibtex insisted
that comma (",") was a separator, not a terminator.  This rule forced
commas to the fronts of lines.  25 years later, bibtex allows commas
to be terminators, but I am too lazy to rework all my .bib files.
Keeping the same format as my .bib files allows my to simply
incorporate my RCU.bib file into Documentation/RCU/RTFP.txt, which
is much easier than my earlier practice of keeping track of what
had changed and adding individual entries.  (I sometimes find relevant
papers that were published some years back, for example.)

In addition, this change adds entries for papers published in the
last year or so.
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
      6ae37718
  39. 19 8月, 2013 1 次提交
  41. 11 6月, 2013 2 次提交
  43. 03 4月, 2013 1 次提交
    • F
      nohz: Rename CONFIG_NO_HZ to CONFIG_NO_HZ_COMMON · 3451d024
      由 Frederic Weisbecker 提交于 
      We are planning to convert the dynticks Kconfig options layout
into a choice menu. The user must be able to easily pick
any of the following implementations: constant periodic tick,
idle dynticks, full dynticks.

As this implies a mutual exclusion, the two dynticks implementions
need to converge on the selection of a common Kconfig option in order
to ease the sharing of a common infrastructure.

It would thus seem pretty natural to reuse CONFIG_NO_HZ to
that end. It already implements all the idle dynticks code
and the full dynticks depends on all that code for now.
So ideally the choice menu would propose CONFIG_NO_HZ_IDLE and
CONFIG_NO_HZ_EXTENDED then both would select CONFIG_NO_HZ.

On the other hand we want to stay backward compatible: if
CONFIG_NO_HZ is set in an older config file, we want to
enable CONFIG_NO_HZ_IDLE by default.

But we can't afford both at the same time or we run into
a circular dependency:

1) CONFIG_NO_HZ_IDLE and CONFIG_NO_HZ_EXTENDED both select
   CONFIG_NO_HZ
2) If CONFIG_NO_HZ is set, we default to CONFIG_NO_HZ_IDLE

We might be able to support that from Kconfig/Kbuild but it
may not be wise to introduce such a confusing behaviour.

So to solve this, create a new CONFIG_NO_HZ_COMMON option
which gathers the common code between idle and full dynticks
(that common code for now is simply the idle dynticks code)
and select it from their referring Kconfig.

Then we'll later create CONFIG_NO_HZ_IDLE and map CONFIG_NO_HZ
to it for backward compatibility.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
      3451d024
  45. 14 3月, 2013 1 次提交
  47. 13 3月, 2013 2 次提交
  49. 17 11月, 2012 2 次提交
  51. 14 11月, 2012 1 次提交
  53. 09 11月, 2012 2 次提交