alpha: Snapshot thread flags

Some thread flags can be set remotely, and so even when IRQs are disabled,
the flags can change under our feet. Generally this is unlikely to cause a
problem in practice, but it is somewhat unsound, and KCSAN will
legitimately warn that there is a data race.

To avoid such issues, a snapshot of the flags has to be taken prior to
using them. Some places already use READ_ONCE() for that, others do not.

Convert them all to the new flag accessor helpers.

Signed-off-by: Mark Rutland <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Paul E. McKenney <[email protected]>
Cc: Ivan Kokshaysky <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Richard Henderson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: mrutland-arm

arch/alpha/kernel/signal.c

@@ -535,6 +535,6 @@ do_work_pending(struct pt_regs *regs, unsigned long thread_flags,
 			}
 		}
 		local_irq_disable();
-		thread_flags = current_thread_info()->flags;
+		thread_flags = read_thread_flags();
 	} while (thread_flags & _TIF_WORK_MASK);
 }