kc3-lang/gnulib/modules/lock

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• Hash : be95b17a
  Author :
  Date : 2017-01-05T12:51:36
  

  lock: Provide guarantee to avoid writer starvation for rwlocks.
  
  The rationale is: 1) Read-preferring read-write locks are prone to
  writer starvation if the number of reader threads multiplied by the
  percentage of time they have the lock held is too high. 2) Write-
  preferring read-write locks are the only reliable way to avoid this.
  3) There have been reports of 'test-lock' hanging on glibc systems
  http://lists.gnu.org/archive/html/bug-gnulib/2017-01/msg00009.html,
  and glibc indeed implements read-preferring rwlocks by default, see
  http://man7.org/linux/man-pages/man3/pthread_rwlockattr_setkind_np.3.html
  and https://sourceware.org/bugzilla/show_bug.cgi?id=13701 .
  
  * m4/pthread_rwlock_rdlock.m4: New file.
  * m4/lock.m4 (gl_LOCK): Invoke gl_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER.
  * lib/glthread/lock.h [USE_POSIX_THREADS]: Test
  HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER. Use a different implementation
  of rwlock initialization on glibc systems without
  HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER. Use a different implementation
  of rwlocks altogether on non-glibc systems without
  HAVE_PTHREAD_RWLOCK_RDLOCK_PREFER_WRITER.
  [USE_PTH_THREADS]: Use a different implementation of rwlocks altogether.
  * lib/glthread/lock.c [USE_POSIX_THREADS]
  (glthread_rwlock_init_for_glibc): New function.
  [USE_POSIX_THREADS] (glthread_rwlock_rdlock_multithreaded): Update
  comment.
  [USE_PTH_THREADS]: New implementation of rwlocks.
  [USE_WINDOWS_THREADS] (glthread_rwlock_rdlock_func): Prefer writers over
  readers.
  * modules/lock (Files): Add m4/pthread_rwlock_rdlock.m4.
  (Depends-on): Add 'extensions'.
  * tests/test-rwlock1.c: New file.
  * lock-tests (Files): Add it.
  (Depends-on): Add usleep.
  (Makefile.am): Add test-rwlock1 to the tests.
  

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• modules/lock

• Description:
  Locking in multithreaded situations.
  
  Files:
  lib/glthread/lock.h
  lib/glthread/lock.c
  m4/lock.m4
  m4/pthread_rwlock_rdlock.m4
  
  Depends-on:
  extensions
  threadlib
  
  configure.ac:
  gl_LOCK
  gl_MODULE_INDICATOR([lock])
  
  Makefile.am:
  lib_SOURCES += glthread/lock.h glthread/lock.c
  
  Include:
  "glthread/lock.h"
  
  Link:
  $(LTLIBTHREAD) when linking with libtool, $(LIBTHREAD) otherwise
  
  License:
  LGPLv2+
  
  Maintainer:
  all
  

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