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bionic: pthread: use private futexes by default for mutexes and condvars

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Private futexes are a recent kernel addition: faster futexes that cannot be
shared between processes. This patch uses them by default, unless the PROCESS_SHARED
attribute flag is used when creating a mutex and/or conditional variable.

Also introduces pthread_condattr_init/destroy/setpshared/getpshared.

Change-Id: I3a0e2116f467072b046524cb5babc00e41057a53
This commit is contained in:
David 'Digit' Turner
2010-03-10 16:44:08 -08:00
parent 1cfbda826c
commit ba9c6f0989
6 changed files with 612 additions and 299 deletions
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10
libc/docs/CHANGES.TXT
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@@ -80,6 +80,16 @@ Differences between current and Android 2.1:
an unknown domain name. Due to an initialization bug, a random DNS search
list was generated for each thread is net.dns.search is not defined.
- <pthread.h>: Add pthread_condattr_init/destroy/setpshared/getpshared.
Also modify mutex and condvar implementation to use private futexes by
default, unless PROCESS_SHARED is specified in the init attributes.
Private futexes are limited to a single address space and can't be shared
among processes. However they are much faster to wake/wait for. This should
speed up mutex and condvar operations.
NOTE: PROCESS_SHARED mutexes are still NOT robust (see note below).
-------------------------------------------------------------------------------
Differences between Android 2.1 and 2.0.1: