Messages in this thread Patch in this message |  | | From | "Per Persson" <> | Subject | [PATCH] {double,triple}_down() in fs.h | Date | Tue, 13 Nov 2001 23:32:47 +0100 |
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This time I've read SubmittingPatches and tried to follow the rules, especially the one saying that a patch shouldn't be sent as an attachment.
The code of triple_down() looked ugly and complicated, but I found that it just sorted the semaphores and down()ed them. So I rewrote the code making it simpler and more efficient.
The patch was made w.r.t 2.4.14.
Per Persson per.persson@gnosjo.pp.se
--- include/linux/fs.h.orig Mon Nov 12 01:14:10 2001 +++ include/linux/fs.h Tue Nov 13 17:35:16 2001 @@ -1478,14 +1478,25 @@ /* * Whee.. Deadlock country. Happily there are only two VFS * operations that does this.. + * + * {double,triple}_down modified by Per Persson in September, 2001 */ + +#define exch(x,y) \ +do { \ + typeof(x) __tmp__ = (x); \ + (x) = (y); \ + (y) = __tmp__; \ +} while(0) + +#define sort(x,y) \ +if((x) < (y)) \ + exch((x), (y)) + static inline void double_down(struct semaphore *s1, struct semaphore *s2) { - if (s1 != s2) { - if ((unsigned long) s1 < (unsigned long) s2) { - struct semaphore *tmp = s2; - s2 = s1; s1 = tmp; - } + if (s1 != s2) + sort((ulong)s1, (ulong)s2); // s1 > s2 down(s1); } down(s2); @@ -1495,9 +1506,10 @@ * Ewwwwwwww... _triple_ lock. We are guaranteed that the 3rd argument is * not equal to 1st and not equal to 2nd - the first case (target is parent of * source) would be already caught, the second is plain impossible (target is - * its own parent and that case would be caught even earlier). Very messy. - * I _think_ that it works, but no warranties - please, look it through. - * Pox on bloody lusers who mandated overwriting rename() for directories... + * its own parent and that case would be caught even earlier). + * + * Cleaner and more efficient code than the original. + * /Per */
static inline void triple_down(struct semaphore *s1, @@ -1505,33 +1517,17 @@ struct semaphore *s3) { if (s1 != s2) { - if ((unsigned long) s1 < (unsigned long) s2) { - if ((unsigned long) s1 < (unsigned long) s3) { - struct semaphore *tmp = s3; - s3 = s1; s1 = tmp; - } - if ((unsigned long) s1 < (unsigned long) s2) { - struct semaphore *tmp = s2; - s2 = s1; s1 = tmp; - } - } else { - if ((unsigned long) s1 < (unsigned long) s3) { - struct semaphore *tmp = s3; - s3 = s1; s1 = tmp; - } - if ((unsigned long) s2 < (unsigned long) s3) { - struct semaphore *tmp = s3; - s3 = s2; s2 = tmp; - } - } + sort((ulong)s1, (ulong)s2); // s1 > s2 + sort((ulong)s1, (ulong)s3); // s1 > s3 down(s1); - } else if ((unsigned long) s2 < (unsigned long) s3) { - struct semaphore *tmp = s3; - s3 = s2; s2 = tmp; } + sort((ulong)s2, (ulong)s3); // s2 > s3 down(s2); down(s3); } + +#undef sort +#undef exch
static inline void double_up(struct semaphore *s1, struct semaphore *s2) { - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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