[PATCH] sparc32 rwlock fix
read_trylock() is broken on sparc32 (doesn't build and didn't work
right, actually). Proposed fix:
- make "writer holds lock" distinguishable from "reader tries to grab
lock"
- have __raw_read_trylock() try to acquire the mutex (in LSB of lock),
terminating spin if we see that there's writer holding it. Then do
the rest as we do in read_lock().
Thanks to Ingo for discussion...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/sparc/lib/locks.S b/arch/sparc/lib/locks.S
index 95fa484..b1df55c 100644
--- a/arch/sparc/lib/locks.S
+++ b/arch/sparc/lib/locks.S
@@ -25,6 +25,15 @@
ldstub [%g1 + 3], %g2
b ___rw_read_enter_spin_on_wlock
ldub [%g1 + 3], %g2
+___rw_read_try_spin_on_wlock:
+ andcc %g2, 0xff, %g0
+ be,a ___rw_read_try
+ ldstub [%g1 + 3], %g2
+ xnorcc %g2, 0x0, %o0 /* if g2 is ~0, set o0 to 0 and bugger off */
+ bne,a ___rw_read_enter_spin_on_wlock
+ ld [%g1], %g2
+ retl
+ mov %g4, %o7
___rw_read_exit_spin_on_wlock:
orcc %g2, 0x0, %g0
be,a ___rw_read_exit
@@ -60,6 +69,17 @@
retl
mov %g4, %o7
+ .globl ___rw_read_try
+___rw_read_try:
+ orcc %g2, 0x0, %g0
+ bne ___rw_read_try_spin_on_wlock
+ ld [%g1], %g2
+ add %g2, 1, %g2
+ st %g2, [%g1]
+ set 1, %o1
+ retl
+ mov %g4, %o7
+
.globl ___rw_write_enter
___rw_write_enter:
orcc %g2, 0x0, %g0