Bug #908

Updated by sjg about 1 year ago

Any suggestions on how to make this clearer are welcome.

Index: notes/porting_drivers.txt
===================================================================
RCS file: /home/aggelos/imports/vcs/dcvs/doc/notes/porting_drivers.txt,v
retrieving revision 1.3
diff -u -p -u -r1.3 porting_drivers.txt
--- notes/porting_drivers.txt 29 Dec 2007 18:35:59 -0000 1.3
+++ notes/porting_drivers.txt 6 Jan 2008 17:40:24 -0000
@@ -84,6 +84,24 @@ $DragonFly: doc/notes/porting_drivers.tx
call is replaced with
lockmgr(&my_lock, LK_EXCLUSIVE|LK_NOWAIT);

+ On occasion, the FreeBSD code will use mtx_sleep() or msleep()
+ (currently [01/2008], those macros have identical definitions)
+ in order to release a mutex and sleep without missing any
+ wakeups that might occur in between. The DragonFly idiom for
+ this case is to enter a critical section and use tsleep_interlock()
+ to let threads in other cpus know that we're about to go to
+ sleep. In our example, you would substitute
+
+ crit_enter();
+ tsleep_interlock(ident);
+ lockmgr(&my_lock, LK_RELEASE);
+ tsleep(ident, flags, "whatever", timeout);
+ crit_exit();
+ lockmgr(&my_lock, LK_EXCLUSIVE);
+
+ for
+ msleep(ident, &my_mtx, flags, "whatever", timeout);
+
As for mtx_assert() calls, translate them like this:

mtx_assert(&my_mtx, MA_OWNED) -> KKASSERT(lockstatus(&my_lock, curthread) != 0)

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