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authorAl Viro <viro@ftp.linux.org.uk>2006-10-08 14:32:15 +0100
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-08 12:32:35 -0700
commit7a39f52202a70ff6834e37053e2ee55c7d351621 (patch)
treede2f029495110336d2dd2b89205db2c62710dd50 /arch/sparc
parent6d24c8dc2e656b02807aa0506405727d34c0376c (diff)
downloadlinux-linaro-stable-7a39f52202a70ff6834e37053e2ee55c7d351621.tar.gz
[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>
Diffstat (limited to 'arch/sparc')
-rw-r--r--arch/sparc/kernel/sparc_ksyms.c4
-rw-r--r--arch/sparc/lib/locks.S20
2 files changed, 23 insertions, 1 deletions
diff --git a/arch/sparc/kernel/sparc_ksyms.c b/arch/sparc/kernel/sparc_ksyms.c
index 4d441a554d35..33dadd9f2871 100644
--- a/arch/sparc/kernel/sparc_ksyms.c
+++ b/arch/sparc/kernel/sparc_ksyms.c
@@ -87,6 +87,7 @@ extern void ___set_bit(void);
extern void ___clear_bit(void);
extern void ___change_bit(void);
extern void ___rw_read_enter(void);
+extern void ___rw_read_try(void);
extern void ___rw_read_exit(void);
extern void ___rw_write_enter(void);
@@ -104,8 +105,9 @@ extern unsigned _Urem(unsigned, unsigned);
EXPORT_SYMBOL(sparc_cpu_model);
EXPORT_SYMBOL(kernel_thread);
#ifdef CONFIG_SMP
-// XXX find what uses (or used) these.
+// XXX find what uses (or used) these. AV: see asm/spinlock.h
EXPORT_SYMBOL(___rw_read_enter);
+EXPORT_SYMBOL(___rw_read_try);
EXPORT_SYMBOL(___rw_read_exit);
EXPORT_SYMBOL(___rw_write_enter);
#endif
diff --git a/arch/sparc/lib/locks.S b/arch/sparc/lib/locks.S
index 95fa48424967..b1df55cb2215 100644
--- a/arch/sparc/lib/locks.S
+++ b/arch/sparc/lib/locks.S
@@ -25,6 +25,15 @@ ___rw_read_enter_spin_on_wlock:
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 @@ ___rw_read_exit:
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