Switch from _Noreturn to __attribute__((noreturn))

Parts of the Linux kernel build system struggle with _Noreturn.  This
results in the following warnings when building on RHEL 8.5, and likely
other environments.  Switch to using the __attribute__((noreturn)).

  warning: objtool: dbuf_free_range()+0x2b8:
    return with modified stack frame
  warning: objtool: dbuf_free_range()+0x0:
    stack state mismatch: cfa1=7+40 cfa2=7+8
  ...
  WARNING: EXPORT symbol "arc_buf_size" [zfs.ko] version generation
    failed, symbol will not be versioned.
  WARNING: EXPORT symbol "spa_open" [zfs.ko] version generation
    failed, symbol will not be versioned.
  ...

Additionally, __thread_exit() has been renamed spl_thread_exit() and
made a static inline function.  This was needed because the kernel
will generate a warning for symbols which are __attribute__((noreturn))
and then exported with EXPORT_SYMBOL.

While we could continue to use _Noreturn in user space I've also
switched it to __attribute__((noreturn)) purely for consistency
throughout the code base.

Reviewed-by: Ryan Moeller <[email protected]>
Reviewed-by: Brian Atkinson <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #13238 

1 files changed, 0 insertions, 9 deletions

diff --git a/module/os/linux/spl/spl-thread.c b/module/os/linux/spl/spl-thread.c
index 16d2ca1b1..32a2d34b1 100644
--- a/module/os/linux/spl/spl-thread.c
+++ b/module/os/linux/spl/spl-thread.c
@@ -62,15 +62,6 @@ thread_generic_wrapper(void *arg)
 	return (0);
 }
 
-void
-__thread_exit(void)
-{
-	tsd_exit();
-	SPL_KTHREAD_COMPLETE_AND_EXIT(NULL, 0);
-	/* Unreachable */
-}
-EXPORT_SYMBOL(__thread_exit);
-
 /*
  * thread_create() may block forever if it cannot create a thread or
  * allocate memory.  This is preferable to returning a NULL which Solaris