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riscv: Fix fully ordered LR/SC xchg[8|16]() implementations

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The fully ordered versions of xchg[8|16]() using LR/SC lack the
necessary memory barriers to guarantee the order.

Fix this by matching what is already implemented in the fully ordered
versions of cmpxchg() using LR/SC.

Suggested-by: Andrea Parri <parri.andrea@gmail.com>
Reported-by: Andrea Parri <parri.andrea@gmail.com>
Closes: https://lore.kernel.org/linux-riscv/ZlYbupL5XgzgA0MX@andrea/T/#u
Fixes: a8ed2b7a2c ("riscv/cmpxchg: Implement xchg for variables of size 1 and 2")
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Andrea Parri <parri.andrea@gmail.com>
Link: https://lore.kernel.org/r/20240530145546.394248-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Alexandre Ghiti 2024-05-30 16:55:46 +02:00 committed by Palmer Dabbelt
parent 982a7eb97b
commit 1d84afaf02
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GPG key ID: 2E1319F35FBB1889
1 changed files with 12 additions and 10 deletions
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22
arch/riscv/include/asm/cmpxchg.h
View file

@ -10,7 +10,7 @@
#include <asm/fence.h>
#define __arch_xchg_masked(prepend, append, r, p, n) \
#define __arch_xchg_masked(sc_sfx, prepend, append, r, p, n) \
({ \
u32 *__ptr32b = (u32 *)((ulong)(p) & ~0x3); \
ulong __s = ((ulong)(p) & (0x4 - sizeof(*p))) * BITS_PER_BYTE; \
@ -25,7 +25,7 @@
"0: lr.w %0, %2\n" \
" and %1, %0, %z4\n" \
" or %1, %1, %z3\n" \
" sc.w %1, %1, %2\n" \
" sc.w" sc_sfx " %1, %1, %2\n" \
" bnez %1, 0b\n" \
append \
: "=&r" (__retx), "=&r" (__rc), "+A" (*(__ptr32b)) \
@ -46,7 +46,8 @@
: "memory"); \
})
#define _arch_xchg(ptr, new, sfx, prepend, append) \
#define _arch_xchg(ptr, new, sc_sfx, swap_sfx, prepend, \
sc_append, swap_append) \
({ \
__typeof__(ptr) __ptr = (ptr); \
__typeof__(*(__ptr)) __new = (new); \
@ -55,15 +56,15 @@
switch (sizeof(*__ptr)) { \
case 1: \
case 2: \
__arch_xchg_masked(prepend, append, \
__arch_xchg_masked(sc_sfx, prepend, sc_append, \
__ret, __ptr, __new); \
break; \
case 4: \
__arch_xchg(".w" sfx, prepend, append, \
__arch_xchg(".w" swap_sfx, prepend, swap_append, \
__ret, __ptr, __new); \
break; \
case 8: \
__arch_xchg(".d" sfx, prepend, append, \
__arch_xchg(".d" swap_sfx, prepend, swap_append, \
__ret, __ptr, __new); \
break; \
default: \
@ -73,16 +74,17 @@
})
#define arch_xchg_relaxed(ptr, x) \
_arch_xchg(ptr, x, "", "", "")
_arch_xchg(ptr, x, "", "", "", "", "")
#define arch_xchg_acquire(ptr, x) \
_arch_xchg(ptr, x, "", "", RISCV_ACQUIRE_BARRIER)
_arch_xchg(ptr, x, "", "", "", \
RISCV_ACQUIRE_BARRIER, RISCV_ACQUIRE_BARRIER)
#define arch_xchg_release(ptr, x) \
_arch_xchg(ptr, x, "", RISCV_RELEASE_BARRIER, "")
_arch_xchg(ptr, x, "", "", RISCV_RELEASE_BARRIER, "", "")
#define arch_xchg(ptr, x) \
_arch_xchg(ptr, x, ".aqrl", "", "")
_arch_xchg(ptr, x, ".rl", ".aqrl", "", RISCV_FULL_BARRIER, "")
#define xchg32(ptr, x) \
({ \