[paulmck-rcu:dev.2024.03.27b 61/69] lib/cmpxchg-emu.c:24:11: warning: no previous prototype for 'cmpxchg_emu_u8'
From: kernel test robot
Date: Fri Mar 29 2024 - 17:27:17 EST
tree: https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2024.03.27b
head: 786fab3085d764055a78edb54023420920344333
commit: b48ffed4c636b96d2be7a93806870772ce34961f [61/69] csky: Emulate one-byte and two-byte cmpxchg
config: csky-allnoconfig (https://download.01.org/0day-ci/archive/20240330/202403300508.Xz7XNp71-lkp@xxxxxxxxx/config)
compiler: csky-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240330/202403300508.Xz7XNp71-lkp@xxxxxxxxx/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202403300508.Xz7XNp71-lkp@xxxxxxxxx/
All warnings (new ones prefixed by >>):
>> lib/cmpxchg-emu.c:24:11: warning: no previous prototype for 'cmpxchg_emu_u8' [-Wmissing-prototypes]
24 | uintptr_t cmpxchg_emu_u8(volatile u8 *p, uintptr_t old, uintptr_t new)
| ^~~~~~~~~~~~~~
>> lib/cmpxchg-emu.c:51:11: warning: no previous prototype for 'cmpxchg_emu_u16' [-Wmissing-prototypes]
51 | uintptr_t cmpxchg_emu_u16(volatile u16 *p, uintptr_t old, uintptr_t new)
| ^~~~~~~~~~~~~~~
vim +/cmpxchg_emu_u8 +24 lib/cmpxchg-emu.c
0bbce967f3ecfc Paul E. McKenney 2024-03-17 22
0bbce967f3ecfc Paul E. McKenney 2024-03-17 23 /* Emulate one-byte cmpxchg() in terms of 4-byte cmpxchg. */
0bbce967f3ecfc Paul E. McKenney 2024-03-17 @24 uintptr_t cmpxchg_emu_u8(volatile u8 *p, uintptr_t old, uintptr_t new)
0bbce967f3ecfc Paul E. McKenney 2024-03-17 25 {
0bbce967f3ecfc Paul E. McKenney 2024-03-17 26 u32 *p32 = (u32 *)(((uintptr_t)p) & ~0x3);
0bbce967f3ecfc Paul E. McKenney 2024-03-17 27 int i = ((uintptr_t)p) & 0x3;
0bbce967f3ecfc Paul E. McKenney 2024-03-17 28 union u8_32 old32;
0bbce967f3ecfc Paul E. McKenney 2024-03-17 29 union u8_32 new32;
0bbce967f3ecfc Paul E. McKenney 2024-03-17 30 u32 ret;
0bbce967f3ecfc Paul E. McKenney 2024-03-17 31
0bbce967f3ecfc Paul E. McKenney 2024-03-17 32 old32.w = READ_ONCE(*p32);
0bbce967f3ecfc Paul E. McKenney 2024-03-17 33 do {
0bbce967f3ecfc Paul E. McKenney 2024-03-17 34 if (old32.b[i] != old)
0bbce967f3ecfc Paul E. McKenney 2024-03-17 35 return old32.b[i];
0bbce967f3ecfc Paul E. McKenney 2024-03-17 36 new32.w = old32.w;
0bbce967f3ecfc Paul E. McKenney 2024-03-17 37 new32.b[i] = new;
0bbce967f3ecfc Paul E. McKenney 2024-03-17 38 instrument_atomic_read_write(p, 1);
0bbce967f3ecfc Paul E. McKenney 2024-03-17 39 ret = data_race(cmpxchg(p32, old32.w, new32.w));
0bbce967f3ecfc Paul E. McKenney 2024-03-17 40 } while (ret != old32.w);
0bbce967f3ecfc Paul E. McKenney 2024-03-17 41 return old;
0bbce967f3ecfc Paul E. McKenney 2024-03-17 42 }
0bbce967f3ecfc Paul E. McKenney 2024-03-17 43 EXPORT_SYMBOL_GPL(cmpxchg_emu_u8);
0bbce967f3ecfc Paul E. McKenney 2024-03-17 44
0bbce967f3ecfc Paul E. McKenney 2024-03-17 45 union u16_32 {
0bbce967f3ecfc Paul E. McKenney 2024-03-17 46 u16 h[2];
0bbce967f3ecfc Paul E. McKenney 2024-03-17 47 u32 w;
0bbce967f3ecfc Paul E. McKenney 2024-03-17 48 };
0bbce967f3ecfc Paul E. McKenney 2024-03-17 49
0bbce967f3ecfc Paul E. McKenney 2024-03-17 50 /* Emulate two-byte cmpxchg() in terms of 4-byte cmpxchg. */
0bbce967f3ecfc Paul E. McKenney 2024-03-17 @51 uintptr_t cmpxchg_emu_u16(volatile u16 *p, uintptr_t old, uintptr_t new)
:::::: The code at line 24 was first introduced by commit
:::::: 0bbce967f3ecfc6da1e7e8756b0d398e791b8dee lib: Add one-byte and two-byte cmpxchg() emulation functions
:::::: TO: Paul E. McKenney <paulmck@xxxxxxxxxx>
:::::: CC: Paul E. McKenney <paulmck@xxxxxxxxxx>
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