sched/headers: Move task_struct::signal and task_struct::sighand types and accessors into <linux/sched/signal.h>

task_struct::signal and task_struct::sighand are pointers, which would normally make it
straightforward to not define those types in sched.h.

That is not so, because the types are accompanied by a myriad of APIs (macros and inline
functions) that dereference them.

Split the types and the APIs out of sched.h and move them into a new header, <linux/sched/signal.h>.

With this change sched.h does not know about 'struct signal' and 'struct sighand' anymore,
trying to put accessors into sched.h as a test fails the following way:

  ./include/linux/sched.h: In function ‘test_signal_types’:
  ./include/linux/sched.h:2461:18: error: dereferencing pointer to incomplete type ‘struct signal_struct’
                    ^

This reduces the size and complexity of sched.h significantly.

Update all headers and .c code that relied on getting the signal handling
functionality from <linux/sched.h> to include <linux/sched/signal.h>.

The list of affected files in the preparatory patch was partly generated by
grepping for the APIs, and partly by doing coverage build testing, both
all[yes|mod|def|no]config builds on 64-bit and 32-bit x86, and an array of
cross-architecture builds.

Nevertheless some (trivial) build breakage is still expected related to rare
Kconfig combinations and in-flight patches to various kernel code, but most
of it should be handled by this patch.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

5 files changed, 10 insertions, 0 deletions

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 5d4208a..85837ab 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -27,6 +27,8 @@
 #include <linux/inetdevice.h>
 #include <linux/workqueue.h>
 #include <linux/in.h>
+#include <linux/sched/signal.h>
+
 #include <net/sock.h>
 #include <net/tcp.h>
 #include <net/smc.h>
diff --git a/net/smc/smc_clc.c b/net/smc/smc_clc.c
index cc6b6f8..e41f594 100644
--- a/net/smc/smc_clc.c
+++ b/net/smc/smc_clc.c
@@ -11,6 +11,8 @@
 
 #include <linux/in.h>
 #include <linux/if_ether.h>
+#include <linux/sched/signal.h>
+
 #include <net/sock.h>
 #include <net/tcp.h>
 
diff --git a/net/smc/smc_close.c b/net/smc/smc_close.c
index 03dfcc6..67a71d1 100644
--- a/net/smc/smc_close.c
+++ b/net/smc/smc_close.c
@@ -9,6 +9,8 @@
  */
 
 #include <linux/workqueue.h>
+#include <linux/sched/signal.h>
+
 #include <net/sock.h>
 
 #include "smc.h"
diff --git a/net/smc/smc_rx.c b/net/smc/smc_rx.c
index 5d18787..c4ef9a4 100644
--- a/net/smc/smc_rx.c
+++ b/net/smc/smc_rx.c
@@ -11,6 +11,8 @@
 
 #include <linux/net.h>
 #include <linux/rcupdate.h>
+#include <linux/sched/signal.h>
+
 #include <net/sock.h>
 
 #include "smc.h"
diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c
index 6e73b28..69a0013 100644
--- a/net/smc/smc_tx.c
+++ b/net/smc/smc_tx.c
@@ -15,6 +15,8 @@
 #include <linux/net.h>
 #include <linux/rcupdate.h>
 #include <linux/workqueue.h>
+#include <linux/sched/signal.h>
+
 #include <net/sock.h>
 
 #include "smc.h"