After a recent improvement in clang to warn on unsequenced accesses to volatile variables [1], an instance appears in show_task(), which can break the build with CONFIG_PPC_WERROR=y / CONFIG_WERROR=y / W=e: arch/powerpc/xmon/xmon.c:3262:3: error: unsequenced accesses to volatile qualified 'tsk' [-Werror,-Wunsequenced] 3261 | printf("%16px %16lx %16px %6d %6d %c %2d %s\n", tsk, | ~~~ 3262 | tsk->thread.ksp, tsk->thread.regs, | ^ Per C11 5.1.2.3.2, accessing a volatile object is a side effect. Per C11 6.5.2, unsequenced side effects on the same scalar object are undefined behavior. Per C11 6.5.2.2.10/12, the evaluation of arguments in a function call is indeterminately sequenced, meaning any side effects in the arguments are unsequenced. tsk was made volatile in commit a2305e3de819 ("powerpc: mark local variables around longjmp as volatile") to ensure its value in show_tasks() was properly restored after returning from a potential longjmp(). Aside from that, the value is not being modified through other means, so rename the volatile parameter and add a local variable named tsk to hold its value throughout show_task(), clearing up the warning. Cc: stable@vger.kernel.org Fixes: a2305e3de819 ("powerpc: mark local variables around longjmp as volatile") Closes: https://github.com/ClangBuiltLinux/linux/issues/2199 Link: https://github.com/llvm/llvm-project/commit/955715460eaf9188c241c74750637fc82dfcc423 [1] Signed-off-by: Nathan Chancellor --- arch/powerpc/xmon/xmon.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c index cb3a3244ae6f..90a8d7a8f42d 100644 --- a/arch/powerpc/xmon/xmon.c +++ b/arch/powerpc/xmon/xmon.c @@ -3240,8 +3240,9 @@ memzcan(void) printf("%.8lx\n", a - mskip); } -static void show_task(struct task_struct *volatile tsk) +static void show_task(struct task_struct *volatile vol_tsk) { + struct task_struct *tsk = vol_tsk; unsigned int p_state = READ_ONCE(tsk->__state); char state; --- base-commit: 7475ea8b58616b33c04afb976cf0fbaad9dd63fb base-tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master change-id: 20261115-xmon-wunsequenced-120aeacf7636 Best regards, -- Cheers, Nathan