xz: Use the self-pipe trick to avoid a race condition with signals.

It is possible that a signal to set user_abort arrives right
before a blocking system call is made. In this case the call
may block until another signal arrives, while the wanted
behavior is to make xz clean up and exit as soon as possible.

After this commit, the race condition is avoided with the
input side which already uses non-blocking I/O. The output
side still uses blocking I/O and thus has the race condition.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/xz/file_io.h b/src/xz/file_io.h
index ef639324..2de33792 100644
--- a/src/xz/file_io.h
+++ b/src/xz/file_io.h
@@ -68,6 +68,14 @@ typedef struct {
 extern void io_init(void);
 
 
+#ifndef TUKLIB_DOSLIKE
+/// \brief      Write a byte to user_abort_pipe[1]
+///
+/// This is called from a signal handler.
+extern void io_write_to_user_abort_pipe(void);
+#endif
+
+
 /// \brief      Disable creation of sparse files when decompressing
 extern void io_no_sparse(void);