Comment 1 for bug 1838508

From chrome/browser/process_singleton_posix.cc:

// When the second process sends the current directory and command line flags to
// the first process, it waits for an ACK message back from the first process
// for a certain time. If there is no ACK message back in time, then the first
// process will be considered as hung for some reason. The second process then
// retrieves the process id from the symbol link and kills it by sending
// SIGKILL. Then the second process starts as normal.

The "read() failed" error message suggests that reading from the socket fails for some reason, so the second process considers the first one hung, and it kills it. The timeout isn't reached, because the default built-in value is 20 seconds, and the problem happens much sooner than that.