I came across a metalink note (Note 786507.1) which describes a very short way to identify the blocker of a session waiting on mutex “cursor: pin S wait on X”. Previously, I thought it could only be analyzed with system state dumps, but the note describes that parameter P2RAW of wait event “cursor: pin S wait on X” contains the blocking session id and the refcount. For 32bit environments the field contains 4 bytes (2 bytes for session id, 2 bytes for refcount). On 64 bit environments, the field contains 8 bytes (4 vs. 4).

select p2raw from v$session where event = ‘cursor: pin S wait on X’

The first 2 or 4 bytes from p2raw have to be converted to dec and point to the blocking Session ID. (SID)