sched/wait: Fix the signal handling fix

sched/wait: Fix the signal handling fix

Jan Stancek reported that I wrecked things for him by fixing things for
Vladimir :/

His report was due to an UNINTERRUPTIBLE wait getting -EINTR, which
should not be possible, however my previous patch made this possible by
unconditionally checking signal_pending().

We cannot use current->state as was done previously, because the
instruction after the store to that variable it can be changed.  We must
instead pass the initial state along and use that.

Fixes: 68985633bccb ("sched/wait: Fix signal handling in bit wait helpers")
Reported-by: Jan Stancek <[email protected]>
Reported-by: Chris Mason <[email protected]>
Tested-by: Jan Stancek <[email protected]>
Tested-by: Vladimir Murzin <[email protected]>
Tested-by: Chris Mason <[email protected]>
Reviewed-by: Paul Turner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Cc: Oleg Nesterov <[email protected]>
Cc: [email protected]
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>