[patch v9 05/10] task isolation: add hook to task exit

[Marcelo Tosatti <mtosatti@redhat.com>]

The logic to disable vmstat worker thread, when entering
nohz full, does not cover all scenarios. For example, it is possible
for the following to happen:
References: <20220127172319.428529308@fuller.cnet>
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Add task isolation specific hook to task exit routines.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

---
 include/linux/task_isolation.h |   11 +++++++++++
 kernel/exit.c                  |    2 ++
 kernel/fork.c                  |    1 +
 kernel/task_isolation.c        |    4 ++++
 4 files changed, 18 insertions(+)

Index: linux-2.6/kernel/exit.c
===================================================================
--- linux-2.6.orig/kernel/exit.c
+++ linux-2.6/kernel/exit.c
@@ -64,6 +64,7 @@
 #include <linux/compat.h>
 #include <linux/io_uring.h>
 #include <linux/kprobes.h>
+#include <linux/task_isolation.h>
 
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
@@ -759,6 +760,7 @@ void __noreturn do_exit(long code)
 	validate_creds_for_do_exit(tsk);
 
 	io_uring_files_cancel();
+	task_isol_exit(tsk);
 	exit_signals(tsk);  /* sets PF_EXITING */
 
 	/* sync mm's RSS info before statistics gathering */
Index: linux-2.6/kernel/fork.c
===================================================================
--- linux-2.6.orig/kernel/fork.c
+++ linux-2.6/kernel/fork.c
@@ -2417,6 +2417,7 @@ bad_fork_free_pid:
 	if (pid != &init_struct_pid)
 		free_pid(pid);
 bad_fork_cleanup_task_isol:
+	task_isol_exit(p);
 	task_isol_free(p);
 bad_fork_cleanup_thread:
 	exit_thread(p);
Index: linux-2.6/kernel/task_isolation.c
===================================================================
--- linux-2.6.orig/kernel/task_isolation.c
+++ linux-2.6/kernel/task_isolation.c
@@ -21,6 +21,10 @@
 #include <linux/mm.h>
 #include <linux/vmstat.h>
 
+void __task_isol_exit(struct task_struct *tsk)
+{
+}
+
 void __task_isol_free(struct task_struct *tsk)
 {
 	if (!tsk->task_isol_info)
Index: linux-2.6/include/linux/task_isolation.h
===================================================================
--- linux-2.6.orig/include/linux/task_isolation.h
+++ linux-2.6/include/linux/task_isolation.h
@@ -27,6 +27,13 @@ static inline void task_isol_free(struct
 		__task_isol_free(tsk);
 }
 
+void __task_isol_exit(struct task_struct *tsk);
+static inline void task_isol_exit(struct task_struct *tsk)
+{
+       if (tsk->task_isol_info)
+               __task_isol_exit(tsk);
+}
+
 int prctl_task_isol_feat_get(unsigned long arg2, unsigned long arg3,
 			     unsigned long arg4, unsigned long arg5);
 int prctl_task_isol_cfg_get(unsigned long arg2, unsigned long arg3,
@@ -57,6 +64,10 @@ static inline void task_isol_free(struct
 {
 }
 
+static inline void task_isol_exit(struct task_struct *tsk)
+{
+}
+
 static inline int prctl_task_isol_feat_get(unsigned long arg2,
 					   unsigned long arg3,
 					   unsigned long arg4,