Linux Certif

Toute la documentation sur la certification Linux LPI

futex

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#include <linux/futex.h>

#include <sys/time.h>



int futex(int *uaddr, int op, int val, const struct timespec *timeout,




          int *uaddr2, int val3);

ÀâÌÀ

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futex(7) ¤ÎÁàºî¤¬¥æ¡¼¥¶¶õ´Ö¤Ç¶¥¹ç¤Ê¤¯´°Î»¤·¤Ê¤«¤Ã¤¿¾ì¹ç¡¢ ¥«¡¼¥Í¥ë¤ËÃçºÛ¤µ¤»¤ë¤¿¤á¤Ë¥·¥¹¥Æ¥à¥³¡¼¥ë¤ò¸Æ¤ÖɬÍפ¬¤¢¤ë¡£ ÃçºÛ¤È¤¤¤¦¤Î¤Ï¡¢¸Æ¤Ó½Ð¤·¥×¥í¥»¥¹¤ò sleep (µ¯¾²ÂÔ¤Á) ¤µ¤»¤¿¤ê¡¢È¿ÂÐ¤Ë ÂÔ¤Á¥×¥í¥»¥¹¤ò wake ¤µ¤»¤¿¤ê¤¹¤ë¤³¤È¤ò°ÕÌ£¤¹¤ë¡£

¤³¤Î´Ø¿ô¤ò¸Æ¤Ó½Ð¤¹¥×¥í¥»¥¹¤Ï futex(7) ¤Ëµ­½Ò¤µ¤ì¤Æ¤¤¤ë¥»¥Þ¥ó¥Æ¥£¥¯¥¹¤ËÃé¼Â¤Ç¤¢¤ë¤³¤È¤¬Í׵ᤵ¤ì¤ë¡£ ¤³¤Î¥»¥Þ¥ó¥Æ¥£¥¯¥¹¤Ë¤Ï°Ü¿¢ÉÔ²Äǽ¤Ê¥¢¥»¥ó¥Ö¥êÌ¿Îá¤ò½ñ¤¯¤³¤È¤¬´Þ¤Þ¤ì¤ë¡£ ¤³¤Î¤³¤È¤Ï¸À¤¤´¹¤¨¤ë¤È futex ¤Î¥æ¡¼¥¶¤Î¤Û¤È¤ó¤É¤Ï¼ÂºÝ¤Ï¥é¥¤¥Ö¥é¥ê¤Îºî¼Ô¤Ç¤¢¤ê¡¢ °ìÈÌ¥¢¥×¥ê¥±¡¼¥·¥ç¥ó¤Î³«È¯¼Ô¤Ç¤Ï¤Ê¤¤¤È¤¤¤¦¤³¤È¤Ç¤¢¤ë¡£

uaddr °ú¿ô¤Ï¡¢¥«¥¦¥ó¥¿¤ò³ÊǼ¤¹¤ë¡¢ ¥¢¥é¥¤¥ó¥á¥ó¥È¤Î·¤Ã¤¿ int ·¿ÊÑ¿ô¤ò»Ø¤·¤Æ¤¤¤ëɬÍפ¬¤¢¤ë¡£ ¼Â¹Ô¤¹¤ëÁàºî¤Ï op ¥Ñ¥é¥á¡¼¥¿¤ò²ð¤·¤Æ¡¢ÃÍ val ¤È¤È¤â¤ËÅϤµ¤ì¤ë¡£

¸½ºß¤Î¤È¤³¤í 5 ¤Ä¤ÎÁàºî¤¬ÄêµÁ¤µ¤ì¤Æ¤¤¤ë:

FUTEX_WAIT

¤³¤ÎÁàºî¤Ï futex ¥¢¥É¥ì¥¹ uaddr ¤Ë»ØÄꤵ¤ì¤¿ÃÍ val ¤¬¤Þ¤À³ÊǼ¤µ¤ì¤Æ¤¤¤ë¤«¤É¤¦¤«¤òÉÔ²ÄʬÁàºî¤Ç¸¡¾Ú¤·¡¢ sleep ¾õÂÖ¤Ç ¤³¤Î futex ¥¢¥É¥ì¥¹¤ËÂФ·¤Æ FUTEX_WAKE ¤¬¼Â¹Ô¤µ¤ì¤ë¤Î¤òÂԤġ£ timeout °ú¿ô¤¬ NULL ¤Ç¤Ê¤¤¾ì¹ç¡¢¤½¤ÎÆâÍÆ¤Ï ÂÔ¤Á»þ´Ö¤ÎºÇÂçÃͤòɽ¤¹¡£NULL ¤Î¾ì¹ç¤Ï̵¸ÂÂç¤òɽ¤¹¡£ °ú¿ô uaddr2 ¤È val3 ¤Ï̵»ë¤µ¤ì¤ë¡£

futex(7) ¤Ë¾È¤é¤·¹ç¤ï¤»¤ë¤È¡¢¤³¤Î¸Æ¤Ó½Ð¤·¤Ï ¥«¥¦¥ó¥È¤Î¥Ç¥¯¥ê¥á¥ó¥È¤ÇÉé¤ÎÃÍ (¶¥¹ç¤òɽ¤¹) ¤Ë¤Ê¤Ã¤¿¾ì¹ç¤Ë¼Â¹Ô¤µ¤ì¡¢ ÊÌ¤Î¥×¥í¥»¥¹¤¬¤½¤Î futex ¤ò²òÊü¤· FUTEX_WAKE ¤ÎÁàºî¤ò¼Â¹Ô¤¹¤ë¤Þ¤Ç sleep ¤¹¤ë¡£

FUTEX_WAKE

¤³¤ÎÁàºî¤Ç¤Ï»ØÄꤷ¤¿ futex ¥¢¥É¥ì¥¹¤ËÂФ·¤ÆÂÔ¤Á¾õÂ֤Π(¤¹¤Ê¤ï¤Á FUTEX_WAIT Ãæ¤Î) ºÇÂç val ¸Ä¤Î¥×¥í¥»¥¹¤ò wake ¤µ¤»¤ë¡£ °ú¿ô timeout, uaddr2, val3 ¤Ï̵»ë¤µ¤ì¤ë¡£

futex(4) ¤Ë¾È¤é¤·¹ç¤ï¤»¤ë¤È¡¢ ¤³¤ÎÁàºî¤Ï ¥«¥¦¥ó¥È¤Î¥¤¥ó¥¯¥ê¥á¥ó¥È¤ÇÂÔ¤Á¥×¥í¥»¥¹¤¬¤¢¤ë¤ÈȽÌÀ¤·¡¢ futex Ãͤ¬ 1 ¤ËÀßÄꤵ¤ì¤¿ (ÍøÍѲÄǽ¤Ç¤¢¤ë¤³¤È¤òɽ¤¹) ¾ì¹ç¤Ë¼Â¹Ô¤µ¤ì¤ë¡£

FUTEX_FD

ÈóƱ´ü¤Î wake ¤ËÂбþ¤¹¤ë¤¿¤á¡¢¤³¤ÎÁàºî¤Ï¥Õ¥¡¥¤¥ë¥Ç¥£¥¹¥¯¥ê¥×¥¿¤ò futex ¤Ë ´ØÏ¢¤Å¤±¤ë¡£ ÊÌ¤Î¥×¥í¥»¥¹¤¬ FUTEX_WAKE ¤ò¼Â¹Ô¤¹¤ë¤È¡¢ ¥×¥í¥»¥¹¤Ï val ¤ÇÅϤµ¤ì¤¿¥·¥°¥Ê¥ëÈÖ¹æ¤Î¥·¥°¥Ê¥ë¤ò¼õ¿®¤¹¤ë¡£ ¸Æ¤Ó½Ð¤·¥×¥í¥»¥¹¤Ï»ÈÍѸ塢ÊÖ¤µ¤ì¤¿¥Õ¥¡¥¤¥ë¥Ç¥£¥¹¥¯¥ê¥×¥¿¤ò ¥¯¥í¡¼¥º¤·¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£ °ú¿ô timeout, uaddr2, val3 ¤Ï̵»ë¤µ¤ì¤ë¡£

¶¥¹ç¾õÂÖ¤òËɻߤ¹¤ë¤¿¤á¡¢¸Æ¤Ó½Ð¤·¥×¥í¥»¥¹¤Ï FUTEX_FD ¤¬Ê֤俤¢¤È futex ¤¬ up ¤µ¤ì¤¿¤«¤É¤¦¤«¤ò³Îǧ¤·¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£

FUTEX_FD ¤Ï¤â¤È¤â¤È¶¥¹ç¤¬µ¯¤­¤ä¤¹¤¤¤¿¤á¡¢ 2007 ǯ 6 ·î¤Ëºï½ü¤µ¤ì¤ëͽÄê¤Ç¤¢¤ë¡£ ¤³¤ì¤ò»ÈÍѤ·¤Æ¤¤¤ë¥¢¥×¥ê¥±¡¼¥·¥ç¥ó¤Ï¡¢¤¹¤°¤Ë½¤Àµ¤¹¤Ù¤­¤Ç¤¢¤ë¡£

FUTEX_REQUEUE (Linux 2.5.70 °Ê¹ß)

¤³¤ÎÁàºî¤Ï¡¢ FUTEX_WAKE ¤¬»È¤ï¤ì¤Æ¤¤¤Æ¡¢¤«¤Ä wake ¤µ¤ì¤Æ¤¤¤ëÁ´¤Æ¤Î¥×¥í¥»¥¹¤¬ ¾¤Î futex ¤ò¼èÆÀ¤¹¤ëɬÍפ¬¤¢¤ë¾ì¹ç¤Ë¡¢ ¡Ö½Ã¤Î·²¤ì¤Î˽Áö (thundering herd)¡×¸ú²Ì¤òÈò¤±¤ë¤¿¤á¤ËƳÆþ¤µ¤ì¤¿¡£ ¤³¤Î¸Æ¤Ó½Ð¤·¤Ï val ¸Ä¤Î¥×¥í¥»¥¹¤ò wake ¤·¡¢¥¢¥É¥ì¥¹ uaddr2 ¤Ç futex ¤òÂԤäƤ¤¤ë¾¤ÎÁ´¤Æ¤Î¥×¥í¥»¥¹¤òºÆÅÙ¥­¥å¡¼¤Ë¤¤¤ì¤ë¡£ °ú¿ô timeout ¤È val3 ¤Ï̵»ë¤µ¤ì¤ë¡£

FUTEX_CMP_REQUEUE (Linux 2.6.7 °Ê¹ß)

¸Î°Õ¤Ë FUTEX_REQUEUE ¤ò»È¤¦¾ì¹ç¤Ë¶¥¹ç¤¬µ¯¤³¤ë¤¿¤á¡¢ FUTEX_CMP_REQUEUE ¤¬Æ³Æþ¤µ¤ì¤¿¡£ ¤³¤ì¤Ï FUTEX_REQUEUE ¤È»÷¤Æ¤¤¤ë¤¬¡¢¾ì½ê uaddr ¤ËÃÍ val3 ¤¬¤Þ¤ÀÊÝ»ý¤µ¤ì¤Æ¤¤¤ë¤«¤òºÇ½é¤Ë¥Á¥§¥Ã¥¯¤¹¤ë¡£ ÊÝ»ý¤µ¤ì¤Æ¤¤¤Ê¤¤¾ì¹ç¡¢¥¨¥é¡¼ EAGAIN ¤¬ÊÖ¤µ¤ì¤ë¡£ °ú¿ô timeout ¤Ï̵»ë¤µ¤ì¤ë¡£

ÊÖ¤êÃÍ

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FUTEX_WAIT

¥×¥í¥»¥¹¤¬ FUTEX_WAKE ¤Î¸Æ¤Ó½Ð¤·¤Ç wake ¤¹¤ë¤È 0 ¤òÊÖ¤¹¡£ ¥¿¥¤¥à¥¢¥¦¥È¤Î¾ì¹ç¡¢ETIMEOUT ¤¬Ê֤롣 futex ¤¬»ØÄꤵ¤ì¤¿ÃͤÈÅù¤·¤¯¤Ê¤¤¾ì¹ç¡¢ ¥¨¥é¡¼ EWOULDBLOCK ¤Ç¼ºÇÔ¤¹¤ë¡£ ¥·¥°¥Ê¥ë¤ò¼õ¿®¤¹¤ë¤È (¤Þ¤¿¤Ï¾¤Îµ¶¤Î wake ¤Ë¤è¤Ã¤Æ) EINTR ¤òÊÖ¤¹¡£

FUTEX_WAKE

wake ¤·¤¿¥×¥í¥»¥¹¤Î¿ô¤òÊÖ¤¹¡£

FUTEX_FD

futex ¤Ë´ØÏ¢¤Å¤±¤é¤ì¤¿¿·¤¿¤Ê¥Õ¥¡¥¤¥ë¥Ç¥£¥¹¥¯¥ê¥×¥¿¤òÊÖ¤¹¡£

FUTEX_REQUEUE

wake ¤·¤¿¥×¥í¥»¥¹¤Î¿ô¤òÊÖ¤¹¡£

FUTEX_CMP_REQUEUE

wake ¤·¤¿¥×¥í¥»¥¹¤Î¿ô¤òÊÖ¤¹¡£

¥¨¥é¡¼

EACCES

futex ¥á¥â¥ê¤ËÆɤ߹þ¤ß¥¢¥¯¥»¥¹¸¢¤¬¤Ê¤«¤Ã¤¿¡£

EAGAIN

FUTEX_CMP_REQUEUE ¤Çͽ´ü¤·¤Ê¤¤ futex Ãͤ¬¸«¤Ä¤«¤Ã¤¿ (¤³¤ì¤Ï¶¥¹ç¤ò¼¨¤·¤Æ¤¤¤ë¤«¤â¤·¤ì¤Ê¤¤¡£ ¤³¤Î¾ì¹ç¤Ï°ÂÁ´¤Ê FUTEX_WAKE ¤ò»È¤¦¤³¤È)¡£

EFAULT

¥æ¡¼¥¶¶õ´Ö¤«¤é timeout ¤Î¾ðÊó¤ò¼èÆÀ¤¹¤ëºÝ¤Ë¥¨¥é¡¼¤¬È¯À¸¤·¤¿¡£

EINVAL

Áàºî¤¬ÄêµÁ¤µ¤ì¤Æ¤¤¤Ê¤¤¡£¤Þ¤¿¤Ï¥Ú¡¼¥¸¡¦¥¢¥é¥¤¥ó¥á¥ó¥È¤Ç¥¨¥é¡¼¤¬È¯À¸¤·¤¿¡£

ENFILE

¥ª¡¼¥×¥ó¤µ¤ì¤Æ¤¤¤ë¥Õ¥¡¥¤¥ë¤ÎÁí¿ô¤¬¥·¥¹¥Æ¥à¤ÎÀ©¸Â¤Ë㤷¤¿¡£

¥Ð¡¼¥¸¥ç¥ó

ºÇ½é¤Î futex Âбþ¤Ï Linux 2.5.7 ¤ÇÁȤ߹þ¤Þ¤ì¤¿¤¬¡¢ ¾åµ­¤Î¥»¥Þ¥ó¥Æ¥£¥¯¥¹¤È¤Ï°Û¤Ê¤ë¡£ ¤³¤³¤Ç¼¨¤µ¤ì¤Æ¤¤¤ë¥»¥Þ¥ó¥Æ¥£¥¯¥¹¤ò»ý¤Ä 4 ¤Ä¤Î°ú¿ô¤Î¥·¥¹¥Æ¥à¥³¡¼¥ë¤Ï¡¢Linux 2.5.40 ¤ÇƳÆþ¤µ¤ì¤¿¡£ Linux 2.5.70 ¤Ç¤Ï 1 ¤Ä¤Î°ú¿ô¤¬Äɲ䵤줿¡£ Linux 2.6.7 ¤Ç¤Ï 6 ÈÖÌܤΰú¿ô¤¬Äɲ䵤줿¡£ ¤³¤ì¤Ï±ø¤¯¡¢s390 ¥¢¡¼¥­¥Æ¥¯¥Á¥ã¾å¤ÎÆÃÊ̤Τâ¤Î¤Ç¤¢¤ë¡£

½àµò

¤³¤Î¥·¥¹¥Æ¥à¥³¡¼¥ë¤Ï Linux Æȼ«¤Ç¤¢¤ë¡£

Ãí°Õ

·«¤êÊÖ¤¹¤¬¡¢Íç¤Î futex ¤Ï¥¨¥ó¥É¥æ¡¼¥¶¤¬Íưפ˻Ȥ¦¤³¤È¤Î¤Ç¤­¤ë³µÇ°¤È¤·¤Æ °Õ¿Þ¤µ¤ì¤¿¤â¤Î¤Ç¤Ï¤Ê¤¤¡£ ¼ÂÁõ¼Ô¤Ï¡¢¥¢¥»¥ó¥Ö¥ê¸À¸ì¤Ë´·¤ì¤Æ¤ª¤ê¡¢°Ê²¼¤Ëµó¤²¤ë futex ¥æ¡¼¥¶¶õ´Ö¥é¥¤¥Ö¥é¥ê¤Î ¥½¡¼¥¹¤òÆɤ߽ª¤¨¤Æ¤¤¤ë¤³¤È¤¬Í׵ᤵ¤ì¤ë¡£

´ØÏ¢¹àÌÜ

futex(7), `Fuss, Futexes and Furwocks: Fast Userlevel Locking in Linux' (proceedings of the Ottawa Linux Symposium 2002), futex ¤Î»ÈÍÑÎã¥é¥¤¥Ö¥é¥ê, futex-*.tar.bz2 <URL:ftp://ftp.nl.kernel.org:/pub/linux/kernel/people/rusty/>.