Implementing Shared/Exclusive Locks

Example 4-4 is a revision of Example 4-3 that uses an sx lock instead of a mutex.

Note

To save space, the functions race_ioctl, race_new, race_find, and race_destroy aren’t listed here, as they haven’t been changed.

Example 4-4. race_sx.c

#include <sys/param.h>
  #include <sys/module.h>
  #include <sys/kernel.h>
  #include <sys/systm.h>

  #include <sys/conf.h>
  #include <sys/uio.h>
  #include <sys/malloc.h>
  #include <sys/ioccom.h>
  #include <sys/queue.h>
  #include <sys/lock.h>
 #include <sys/sx.h> #include "race_ioctl.h" MALLOC_DEFINE(M_RACE, "race", "race object"); struct race_softc { LIST_ENTRY(race_softc) list; int unit; }; ...

Get FreeBSD Device Drivers now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.

Start your free trial