The patch titled
PI-futex: rt-mutex docs
has been removed from the -mm tree. Its filename is
pi-futex-rt-mutex-docs.patch
This patch was probably dropped from -mm because
it has now been merged into a subsystem tree or
into Linus's tree, or because it was folded into
its parent patch in the -mm tree.
------------------------------------------------------
Subject: PI-futex: rt-mutex docs
From: Ingo Molnar <mingo@xxxxxxx>
Add rt-mutex documentation.
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
Documentation/rtmutex.txt | 60 ++++++++++++++++++++++++++++++++++++
1 files changed, 60 insertions(+)
diff -puN /dev/null Documentation/rtmutex.txt
--- /dev/null 2003-09-15 06:40:47.000000000 -0700
+++ devel-akpm/Documentation/rtmutex.txt 2006-03-25 19:05:05.000000000 -0800
@@ -0,0 +1,60 @@
+RT Mutex Subsystem with PI support
+
+RT Mutexes with priority inheritance are used to support pthread_mutexes
+with priority inheritance attributes.
+
+The basic technology was developed in the preempt-rt tree and
+streamlined for the pthread_mutex support.
+
+RT Mutexes extend the semantics of Mutexes by the priority inheritance
+protocol. Sharing code and data structures with the Mutex code is not
+feasible due to the extended requirements of RT Mutexes.
+
+Basic operation principle:
+
+A low priority owner of a rt_mutex inherits the priority of a higher
+priority waiter until the mutex is released. Is the temporary priority
+boosted owner blocked on a rt_mutex itself it propagates the priority
+boosting to the owner of the rt_mutex it is blocked on. The priority
+boosting is immidiately removed once the rt_mutex has been unlocked.
+This technology allows to shorten the blocking on mutexes which
+protect shared resources. Priority inheritance is not a magic bullet
+for poorly designed applications, but allows optimizations in cases
+where the protection of shared resources might affect critical parts
+of an high priority thread.
+
+The enqueueing of the waiters into the rtmutex waiter list is done in
+priority order. In case of the same priority FIFO order is chosen. Per
+rtmutex only the top priority waiter is enqueued into the owners
+priority waiters list. Also this list enqueues in priority
+order. Whenever the top priority waiter of a task is changed the
+priority of the task is readjusted. The priority enqueueing is handled
+by plists, see also include/linux/plist.h for further explanation.
+
+RT Mutexes are optimized for fastpath operations and have no runtime
+overhead in case of locking an uncontended mutex or unlocking a mutex
+without waiters. The optimized fathpath operations require cmpxchg
+support.
+
+The state of the rtmutex is tracked via the owner field of the
+rt_mutex structure:
+
+rt_mutex->owner holds the task_struct pointer of the owner. Bit 0 and
+1 are used to keep track of the "owner is pending" and "rtmutex has
+waiters" state.
+
+owner bit1 bit0
+NULL 0 0 mutex is free (fast acquire possible)
+NULL 0 1 invalid state
+NULL 1 0 invalid state
+NULL 1 1 invalid state
+taskpointer 0 0 mutex is held (fast release possible)
+taskpointer 0 1 task is pending owner
+taskpointer 1 0 mutex is held and has waiters
+taskpointer 1 1 task is pending owner and mutex has more waiters
+
+Pending ownership is assigned to the first (highest priority) waiter
+of the mutex, when the mutex is released. The thread is woken up and
+can now acquire the mutex. Until the mutex is taken (bit 0 cleared) a
+competing higher priority thread can steal the mutex which puts the
+woken up thread back on the waiters list.
_
Patches currently in -mm which might be from mingo@xxxxxxx are
git-acpi.patch
fix-drivers-mfd-ucb1x00-corec-irq-probing-bug.patch
git-infiniband.patch
git-netdev-all.patch
fix-for-serial-uart-lockup.patch
swapless-pm-add-r-w-migration-entries-fix.patch
i386-break-out-of-recursion-in-stackframe-walk.patch
x86-re-enable-generic-numa.patch
vdso-randomize-the-i386-vdso-by-moving-it-into-a-vma.patch
vdso-randomize-the-i386-vdso-by-moving-it-into-a-vma-tidy.patch
vdso-randomize-the-i386-vdso-by-moving-it-into-a-vma-arch_vma_name-fix.patch
work-around-ppc64-bootup-bug-by-making-mutex-debugging-save-restore-irqs.patch
kernel-kernel-cpuc-to-mutexes.patch
cond-resched-might-sleep-fix.patch
define-__raw_get_cpu_var-and-use-it.patch
ide-cd-end-of-media-error-fix.patch
spin-rwlock-init-cleanups.patch
time-clocksource-infrastructure.patch
sched-comment-bitmap-size-accounting.patch
sched-fix-interactive-ceiling-code.patch
sched-implement-smpnice.patch
sched-protect-calculation-of-max_pull-from-integer-wrap.patch
sched-store-weighted-load-on-up.patch
sched-add-discrete-weighted-cpu-load-function.patch
sched-prevent-high-load-weight-tasks-suppressing-balancing.patch
sched-improve-stability-of-smpnice-load-balancing.patch
sched-improve-smpnice-load-balancing-when-load-per-task.patch
smpnice-dont-consider-sched-groups-which-are-lightly-loaded-for-balancing.patch
smpnice-dont-consider-sched-groups-which-are-lightly-loaded-for-balancing-fix.patch
sched-modify-move_tasks-to-improve-load-balancing-outcomes.patch
sched-avoid-unnecessarily-moving-highest-priority-task-move_tasks.patch
sched-avoid-unnecessarily-moving-highest-priority-task-move_tasks-fix-2.patch
sched_domain-handle-kmalloc-failure.patch
sched_domain-handle-kmalloc-failure-fix.patch
sched_domain-dont-use-gfp_atomic.patch
sched_domain-use-kmalloc_node.patch
sched_domain-allocate-sched_group-structures-dynamically.patch
sched-add-above-background-load-function.patch
mm-implement-swap-prefetching-fix.patch
pi-futex-rt-mutex-docs.patch
pi-futex-rt-mutex-debug.patch
pi-futex-rt-mutex-tester.patch
pi-futex-rt-mutex-futex-api.patch
pi-futex-futex_lock_pi-futex_unlock_pi-support.patch
pi-futex-v2.patch
pi-futex-v3.patch
pi-futex-patchset-v4.patch
pi-futex-patchset-v4-update.patch
pi-futex-patchset-v4-fix.patch
rtmutex-remove-buggy-bug_on-in-pi-boosting-code.patch
futex-pi-enforce-waiter-bit-when-owner-died-is-detected.patch
rtmutex-debug-printk-correct-task-information.patch
futex-pi-make-use-of-restart_block-when-interrupted.patch
document-futex-pi-design.patch
futex_requeue-optimization.patch
reiser4.patch
reiser4-spin-rwlock-init-cleanups.patch
genirq-rename-desc-handler-to-desc-chip.patch
genirq-rename-desc-handler-to-desc-chip-power-fix.patch
genirq-rename-desc-handler-to-desc-chip-ia64-fix.patch
genirq-rename-desc-handler-to-desc-chip-ia64-fix-2.patch
genirq-sem2mutex-probe_sem-probing_active.patch
genirq-cleanup-merge-irq_affinity-into-irq_desc.patch
genirq-cleanup-remove-irq_descp.patch
genirq-cleanup-remove-fastcall.patch
genirq-cleanup-misc-code-cleanups.patch
genirq-cleanup-reduce-irq_desc_t-use-mark-it-obsolete.patch
genirq-cleanup-include-linux-irqh.patch
genirq-cleanup-merge-irq_dir-smp_affinity_entry-into-irq_desc.patch
genirq-cleanup-merge-pending_irq_cpumask-into-irq_desc.patch
genirq-cleanup-turn-arch_has_irq_per_cpu-into-config_irq_per_cpu.patch
genirq-debug-better-debug-printout-in-enable_irq.patch
genirq-add-retrigger-irq-op-to-consolidate-hw_irq_resend.patch
genirq-doc-comment-include-linux-irqh-structures.patch
genirq-doc-handle_irq_event-and-__do_irq-comments.patch
genirq-cleanup-no_irq_type-cleanups.patch
genirq-doc-add-design-documentation.patch
genirq-add-genirq-sw-irq-retrigger.patch
genirq-add-irq_noprobe-support.patch
genirq-add-irq_norequest-support.patch
genirq-add-irq_noautoen-support.patch
genirq-update-copyrights.patch
genirq-core.patch
genirq-add-irq-chip-support.patch
genirq-add-handle_bad_irq.patch
genirq-add-irq-wake-power-management-support.patch
genirq-add-sa_trigger-support.patch
genirq-cleanup-no_irq_type-no_irq_chip-rename.patch
genirq-convert-the-x86_64-architecture-to-irq-chips.patch
genirq-convert-the-i386-architecture-to-irq-chips.patch
genirq-convert-the-i386-architecture-to-irq-chips-fix-2.patch
genirq-more-verbose-debugging-on-unexpected-irq-vectors.patch
detect-atomic-counter-underflows.patch
debug-shared-irqs.patch
make-frame_pointer-default=y.patch
mutex-subsystem-synchro-test-module.patch
vdso-print-fatal-signals.patch
vdso-improve-print_fatal_signals-support-by-adding-memory-maps.patch
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