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authorAl Viro <viro@ftp.linux.org.uk>2006-10-08 09:32:15 -0400
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-08 15:32:35 -0400
commit7a39f52202a70ff6834e37053e2ee55c7d351621 (patch)
treede2f029495110336d2dd2b89205db2c62710dd50 /arch
parent6d24c8dc2e656b02807aa0506405727d34c0376c (diff)
[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')
-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);
87extern void ___clear_bit(void); 87extern void ___clear_bit(void);
88extern void ___change_bit(void); 88extern void ___change_bit(void);
89extern void ___rw_read_enter(void); 89extern void ___rw_read_enter(void);
90extern void ___rw_read_try(void);
90extern void ___rw_read_exit(void); 91extern void ___rw_read_exit(void);
91extern void ___rw_write_enter(void); 92extern void ___rw_write_enter(void);
92 93
@@ -104,8 +105,9 @@ extern unsigned _Urem(unsigned, unsigned);
104EXPORT_SYMBOL(sparc_cpu_model); 105EXPORT_SYMBOL(sparc_cpu_model);
105EXPORT_SYMBOL(kernel_thread); 106EXPORT_SYMBOL(kernel_thread);
106#ifdef CONFIG_SMP 107#ifdef CONFIG_SMP
107// XXX find what uses (or used) these. 108// XXX find what uses (or used) these. AV: see asm/spinlock.h
108EXPORT_SYMBOL(___rw_read_enter); 109EXPORT_SYMBOL(___rw_read_enter);
110EXPORT_SYMBOL(___rw_read_try);
109EXPORT_SYMBOL(___rw_read_exit); 111EXPORT_SYMBOL(___rw_read_exit);
110EXPORT_SYMBOL(___rw_write_enter); 112EXPORT_SYMBOL(___rw_write_enter);
111#endif 113#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:
25 ldstub [%g1 + 3], %g2 25 ldstub [%g1 + 3], %g2
26 b ___rw_read_enter_spin_on_wlock 26 b ___rw_read_enter_spin_on_wlock
27 ldub [%g1 + 3], %g2 27 ldub [%g1 + 3], %g2
28___rw_read_try_spin_on_wlock:
29 andcc %g2, 0xff, %g0
30 be,a ___rw_read_try
31 ldstub [%g1 + 3], %g2
32 xnorcc %g2, 0x0, %o0 /* if g2 is ~0, set o0 to 0 and bugger off */
33 bne,a ___rw_read_enter_spin_on_wlock
34 ld [%g1], %g2
35 retl
36 mov %g4, %o7
28___rw_read_exit_spin_on_wlock: 37___rw_read_exit_spin_on_wlock:
29 orcc %g2, 0x0, %g0 38 orcc %g2, 0x0, %g0
30 be,a ___rw_read_exit 39 be,a ___rw_read_exit
@@ -60,6 +69,17 @@ ___rw_read_exit:
60 retl 69 retl
61 mov %g4, %o7 70 mov %g4, %o7
62 71
72 .globl ___rw_read_try
73___rw_read_try:
74 orcc %g2, 0x0, %g0
75 bne ___rw_read_try_spin_on_wlock
76 ld [%g1], %g2
77 add %g2, 1, %g2
78 st %g2, [%g1]
79 set 1, %o1
80 retl
81 mov %g4, %o7
82
63 .globl ___rw_write_enter 83 .globl ___rw_write_enter
64___rw_write_enter: 84___rw_write_enter:
65 orcc %g2, 0x0, %g0 85 orcc %g2, 0x0, %g0