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Steven Rostedt 77ae365eca ring-buffer: make lockless 
This patch converts the ring buffers into a completely lockless
buffer recording system. The read side still takes locks since
we still serialize readers. But the writers are the ones that
must be lockless (those can happen in NMIs).

The main change is to the "head_page" pointer. We write to the
tail, and read from the head. The "head_page" pointer in the cpu
buffer is now just a reference to where to look. The real head
page is now kept in the head_page->list->prev->next pointer.
That is, in the list head of the previous page we set flags.

The list pages are allocated to be aligned such that the lowest
significant bits are always zero pointing to the list. This gives
us play to put in flags to their pointers.

bit 0: set when the page is a head page
bit 1: set when the writer is moving the page (for overwrite mode)

cmpxchg is used to update the pointer.

When the writer wraps the buffer and the tail meets the head,
in overwrite mode, the writer must move the head page forward.
It first uses cmpxchg to change the pointer flag from 1 to 2.
Once this is done, the reader on another CPU will not take the
page from the buffer.

The writers need to protect against interrupts (we don't bother with
disabling interrupts because NMIs are allowed to write too).

After the writer sets the pointer flag to 2, it takes care to
manage interrupts coming in. This is discribed in detail within the
comments of the code.

 Changes in version 2:
  - Let reader reset entries value of header page.
  - Fix tail page passing commit page on reader page test.
  - Always increment entries and write counter in rb_tail_page_update
  - Add safety check in rb_set_commit_to_write to break out of infinite loop
  - add mask in rb_is_reader_page

[ Impact: lock free writing to the ring buffer ]

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2009-07-07 18:36:12 -04:00
..
gcov gcov: enable GCOV_PROFILE_ALL for x86_64 2009-06-18 13:03:58 -07:00
irq Merge branch 'irq-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-06-20 11:30:01 -07:00
power mm, PM/Freezer: Disable OOM killer when tasks are frozen 2009-06-16 19:47:40 -07:00
time Merge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-06-20 10:51:44 -07:00
trace ring-buffer: make lockless 2009-07-07 18:36:12 -04:00
.gitignore
acct.c [CVE-2009-0029] System call wrappers part 04 2009-01-14 14:15:19 +01:00
async.c async: Fix lack of boot-time console due to insufficient synchronization 2009-06-08 12:31:53 -07:00
audit.c Audit: remove spaces from audit_log_d_path 2009-04-05 13:49:04 -04:00
audit.h fixing audit rule ordering mess, part 1 2009-01-04 15:14:41 -05:00
audit_tree.c Switch collect_mounts() to struct path 2009-06-11 21:36:01 -04:00
auditfilter.c inotify: use GFP_NOFS in kernel_event() to work around a lockdep false-positive 2009-05-06 16:36:09 -07:00
auditsc.c Audit: remove spaces from audit_log_d_path 2009-04-05 13:49:04 -04:00
backtracetest.c
bounds.c
capability.c [CVE-2009-0029] System call wrappers part 04 2009-01-14 14:15:19 +01:00
cgroup.c cgroups: forbid noprefix if mounting more than just cpuset subsystem 2009-06-18 13:03:46 -07:00
cgroup_debug.c debug cgroup: remove unneeded cgroup_lock 2009-04-02 19:04:54 -07:00
cgroup_freezer.c
compat.c signals: implement sys_rt_tgsigqueueinfo 2009-04-30 19:24:24 +02:00
configs.c
cpu.c mm/init: cpu_hotplug_init() must be initialized before SLAB 2009-06-22 21:18:12 -07:00
cpuset.c cpuset,mm: update tasks' mems_allowed in time 2009-06-16 19:47:31 -07:00
cred-internals.h
cred.c CRED: Rename cred_exec_mutex to reflect that it's a guard against ptrace 2009-05-11 08:15:36 +10:00
delayacct.c schedstat: consolidate per-task cpu runtime stats 2008-12-18 13:54:01 +01:00
dma-coherent.c dma-coherent: Restore dma_alloc_from_coherent() large alloc fall back policy. 2009-01-21 18:51:53 +09:00
dma.c
exec_domain.c Get rid of indirect include of fs_struct.h 2009-03-31 23:00:27 -04:00
exit.c ptrace: wait_task_zombie: do not account traced sub-threads 2009-06-19 16:46:06 -07:00
extable.c Merge branch 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-04-05 11:04:19 -07:00
fork.c copy_process(): remove the unneeded clear_tsk_thread_flag(TIF_SIGPENDING) 2009-06-18 13:03:52 -07:00
freezer.c
futex.c futex: fix restart in wait_requeue_pi 2009-05-20 10:34:32 +02:00
futex_compat.c
groups.c groups: move code to kernel/groups.c 2009-06-16 19:47:48 -07:00
hrtimer.c Merge branch 'linux-next' of git://git.infradead.org/ubifs-2.6 2009-06-17 09:46:33 -07:00
hung_task.c softlockup: ensure the task has been switched out once 2009-02-11 11:04:16 +01:00
itimer.c timers: split process wide cpu clocks/timers 2009-02-05 13:04:33 +01:00
kallsyms.c kernel/kallsyms.c: replace deprecated __initcall with device_initcall and fix whitespace 2009-06-09 22:37:52 +02:00
Kconfig.freezer
Kconfig.hz
Kconfig.preempt rcu: provide RCU options on non-preempt architectures too 2008-12-25 09:31:28 +01:00
kexec.c PM core: rename suspend and resume functions 2009-06-12 21:32:31 +02:00
kfifo.c kernel/kfifo.c: replace conditional test with is_power_of_2() 2009-06-16 19:47:47 -07:00
kgdb.c sysrq, intel_fb: fix sysrq g collision 2009-05-15 07:56:24 -05:00
kmod.c kmod: Release sub_info on cred allocation failure. 2009-05-26 12:11:19 -07:00
kprobes.c kprobes: Clean up insn_pages by using list instead of hlist 2009-07-01 10:43:41 +02:00
ksysfs.c kernel/ksysfs.c:fix dependence on CONFIG_NET 2009-01-06 10:44:31 -08:00
kthread.c kthreads: rework kthread_stop() 2009-06-18 13:03:54 -07:00
latencytop.c sched, latencytop: incorporate review feedback from Andrew Morton 2009-02-11 10:18:04 +01:00
lockdep.c Merge branch 'linus' into tracing/core 2009-05-07 11:17:34 +02:00
lockdep_internals.h lockdep: increase MAX_LOCKDEP_ENTRIES and MAX_LOCKDEP_CHAINS 2009-05-12 19:59:52 +02:00
lockdep_proc.c lockstat: warn about disabled lock debugging 2009-02-14 23:28:28 +01:00
lockdep_states.h lockdep: move state bit definitions around 2009-02-14 23:27:59 +01:00
Makefile ring-buffer: Make it generally available 2009-06-25 10:31:30 +02:00
marker.c
module.c kernel: constructor support 2009-06-18 13:03:57 -07:00
mutex-debug.c mutex: implement adaptive spinning 2009-01-14 18:09:02 +01:00
mutex-debug.h mutex: implement adaptive spinning 2009-01-14 18:09:02 +01:00
mutex.c Merge branch 'linus' into perfcounters/core 2009-06-11 17:55:42 +02:00
mutex.h mutex: implement adaptive spinning 2009-01-14 18:09:02 +01:00
notifier.c Merge commit 'v2.6.28-rc6' into core/debug 2008-11-26 08:22:50 +01:00
ns_cgroup.c cgroups: relax ns_can_attach checks to allow attaching to grandchild cgroups 2009-04-02 19:04:53 -07:00
nsproxy.c nsproxy: extract create_nsproxy() 2009-06-18 13:03:56 -07:00
panic.c Fix caller information for warn_slowpath_null 2009-05-16 13:41:28 -07:00
params.c module_param: allow 'bool' module_params to be bool, not just int. 2009-06-12 21:46:58 +09:30
perf_counter.c perf_counter: Push perf_sample_data through the swcounter code 2009-06-20 12:30:30 +02:00
pid.c pids: clean up find_task_by_pid variants 2009-06-18 13:03:55 -07:00
pid_namespace.c pidns: rewrite copy_pid_ns() 2009-06-18 13:03:55 -07:00
pm_qos_params.c
posix-cpu-timers.c kernel/posix-cpu-timers.c: fix sparse warning 2009-04-30 08:08:31 +02:00
posix-timers.c [CVE-2009-0029] System call wrappers part 05 2009-01-14 14:15:20 +01:00
printk.c printk: Add KERN_DEFAULT printk log-level 2009-06-16 11:02:28 -07:00
profile.c page allocator: do not check NUMA node ID when the caller knows the node is valid 2009-06-16 19:47:32 -07:00
ptrace.c ptrace: don't take tasklist to get/set ->last_siginfo 2009-06-18 13:03:52 -07:00
rcuclassic.c kmemtrace, rcu: fix linux/rcutree.h and linux/rcuclassic.h dependencies 2009-04-03 12:23:02 +02:00
rcupdate.c RCU: Don't try and predeclare inline funcs as it upsets some versions of gcc 2009-04-15 13:55:14 -07:00
rcupreempt.c rcu: rcu_sched_grace_period(): kill the bogus flush_signals() 2009-05-05 20:28:05 +02:00
rcupreempt_trace.c "Tree RCU": scalable classic RCU implementation 2008-12-18 21:56:04 +01:00
rcutorture.c cpumask: convert rcutorture.c 2009-03-30 22:05:16 +10:30
rcutree.c rcu: Add __rcu_pending tracing to hierarchical RCU 2009-04-14 11:33:43 +02:00
rcutree.h kmemtrace, rcu: fix rcu_tree_trace.c data structure dependencies 2009-04-03 12:23:03 +02:00
rcutree_trace.c rcu: Add __rcu_pending tracing to hierarchical RCU 2009-04-14 11:33:43 +02:00
relay.c Merge branch 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-04-05 11:04:19 -07:00
res_counter.c memcg: add interface to reset limits 2009-06-18 13:03:48 -07:00
resource.c Remove 'recurse into child resources' logic from 'reserve_region_with_split()' 2009-04-18 21:44:24 -07:00
rtmutex-debug.c
rtmutex-debug.h
rtmutex-tester.c
rtmutex.c trivial: fix ETIMEOUT -> ETIMEDOUT typos 2009-06-12 18:01:50 +02:00
rtmutex.h
rtmutex_common.h rt_mutex: add proxy lock routines 2009-04-06 11:14:02 +02:00
rwsem.c
sched.c Merge branch 'perfcounters-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-06-20 11:29:32 -07:00
sched_clock.c sched: Fix fallback sched_clock()'s offset when using jiffies 2009-05-09 10:08:19 +02:00
sched_cpupri.c sched: Remove unneeded __ref tag 2009-06-17 16:08:04 +02:00
sched_cpupri.h cpumask: remove cpumask_t from core 2009-03-30 22:05:17 +10:30
sched_debug.c sched: Hide runqueues from direct refer at source code level 2009-06-17 18:29:42 +02:00
sched_fair.c sched: Fix out of scope variable access in sched_slice() 2009-06-17 18:37:54 +02:00
sched_features.h Merge branch 'locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-03-30 17:17:35 -07:00
sched_idletask.c sched, timers: move calc_load() to scheduler 2009-05-15 15:32:45 +02:00
sched_rt.c cpumask: alloc zeroed cpumask for static cpumask_var_ts 2009-06-09 22:30:27 +09:30
sched_stats.h sched: remove unused fields from struct rq 2009-03-24 23:16:51 +01:00
seccomp.c x86-64: seccomp: fix 32/64 syscall hole 2009-03-02 15:41:30 -08:00
semaphore.c
signal.c ptrace: do_notify_parent_cldstop: fix the wrong ->nsproxy usage 2009-06-18 13:03:52 -07:00
slow-work.c slow-work: use round_jiffies() for thread pool's cull and OOM timers 2009-06-16 19:47:49 -07:00
smp.c cpumask: alloc zeroed cpumask for static cpumask_var_ts 2009-06-09 22:30:27 +09:30
softirq.c softirq: introduce statistics for softirq 2009-06-18 13:03:40 -07:00
softlockup.c softlockup: decouple hung tasks check from softlockup detection 2009-01-16 14:06:04 +01:00
spinlock.c Allow rwlocks to re-enable interrupts 2009-04-02 19:05:11 -07:00
srcu.c
stacktrace.c stacktrace: provide save_stack_trace_tsk() weak alias 2008-12-25 11:44:43 +01:00
stop_machine.c cpumask: remove cpumask_t from core 2009-03-30 22:05:17 +10:30
sys.c groups: move code to kernel/groups.c 2009-06-16 19:47:48 -07:00
sys_ni.c Merge commit 'v2.6.29-rc2' into perfcounters/core 2009-01-21 16:37:27 +01:00
sysctl.c sysctl.c: remove unused variable 2009-06-18 13:03:54 -07:00
sysctl_check.c net: add ARP notify option for devices 2009-02-01 01:04:33 -08:00
taskstats.c cpumask: convert rest of files in kernel/ 2009-01-01 10:12:28 +10:30
test_kprobes.c kprobes: add tests for register_kprobes 2009-01-06 15:59:20 -08:00
time.c [CVE-2009-0029] System call wrappers part 01 2009-01-14 14:15:18 +01:00
timeconst.pl
timer.c Merge branch 'timers-for-linus-migration' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2009-06-15 10:06:19 -07:00
tracepoint.c tracepoints: dont update zero-sized tracepoint sections 2009-03-18 19:55:00 +01:00
tsacct.c Fix fixpoint divide exception in acct_update_integrals 2009-03-09 08:13:35 -07:00
uid16.c [CVE-2009-0029] System call wrappers part 19 2009-01-14 14:15:26 +01:00
up.c smp_call_function_single(): be slightly less stupid, fix #2 2009-01-12 16:04:37 +01:00
user.c sched: delayed cleanup of user_struct 2009-06-15 21:30:23 -07:00
user_namespace.c Fix recursive lock in free_uid()/free_user_ns() 2009-02-27 16:26:21 -08:00
utsname.c utsns: extract creeate_uts_ns() 2009-06-18 13:03:55 -07:00
utsname_sysctl.c proc_sysctl: use CONFIG_PROC_SYSCTL around ipc and utsname proc_handlers 2009-04-02 19:05:01 -07:00
wait.c wait: don't use __wake_up_common() 2009-04-14 17:17:16 +02:00
workqueue.c ftrace, workqueuetrace: make workqueue tracepoints use TRACE_EVENT macro 2009-06-02 01:10:40 +02:00