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authorMatt Evans <mev@rivosinc.com>2023-02-01 18:39:48 +0000
committerArnd Bergmann <arnd@arndb.de>2023-02-03 15:31:23 +0100
commit6246541522845a443b7ae4a8f0e16facc5a91198 (patch)
tree7dccf933fb3a592cf1abc68b044f637041e83d67 /include/asm-generic
parent88603b6dc419445847923fcb7fe5080067a30f98 (diff)
locking/atomic: cmpxchg: Make __generic_cmpxchg_local compare against zero-extended 'old' value
__generic_cmpxchg_local takes unsigned long old/new arguments which might end up being up-cast from smaller signed types (which will sign-extend). The loaded compare value must be compared against a truncated smaller type, so down-cast appropriately for each size. The issue is apparent on 64-bit machines with code, such as atomic_dec_unless_positive(), that sign-extends from int. 64-bit machines generally don't use the generic cmpxchg but development/early ports might make use of it, so make it correct. Signed-off-by: Matt Evans <mev@rivosinc.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'include/asm-generic')
-rw-r--r--include/asm-generic/cmpxchg-local.h6
1 files changed, 3 insertions, 3 deletions
diff --git a/include/asm-generic/cmpxchg-local.h b/include/asm-generic/cmpxchg-local.h
index 380cdc824e4b..c3e7315b7c1d 100644
--- a/include/asm-generic/cmpxchg-local.h
+++ b/include/asm-generic/cmpxchg-local.h
@@ -26,15 +26,15 @@ static inline unsigned long __generic_cmpxchg_local(volatile void *ptr,
raw_local_irq_save(flags);
switch (size) {
case 1: prev = *(u8 *)ptr;
- if (prev == old)
+ if (prev == (u8)old)
*(u8 *)ptr = (u8)new;
break;
case 2: prev = *(u16 *)ptr;
- if (prev == old)
+ if (prev == (u16)old)
*(u16 *)ptr = (u16)new;
break;
case 4: prev = *(u32 *)ptr;
- if (prev == old)
+ if (prev == (u32)old)
*(u32 *)ptr = (u32)new;
break;
case 8: prev = *(u64 *)ptr;