[patch v6 05/10] task isolation: add hook to task exit

[Marcelo Tosatti]

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: <20211112121642.693790927@fedora.localdomain>
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Add task isolation specific hook to task exit routines.

Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>

---
 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/rcuwait.h>
 #include <linux/compat.h>
 #include <linux/io_uring.h>
+#include <linux/task_isolation.h>
 
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
@@ -778,6 +779,7 @@ void __noreturn do_exit(long code)
 	}
 
 	io_uring_files_cancel();
+	tsk_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
@@ -2446,6 +2446,7 @@ bad_fork_free_pid:
 	if (pid != &init_struct_pid)
 		free_pid(pid);
 bad_fork_cleanup_task_isolation:
+	tsk_isol_exit(p);
 	tsk_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 __tsk_isol_exit(struct task_struct *tsk)
+{
+}
+
 void __tsk_isol_free(struct task_struct *tsk)
 {
 	if (!tsk->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 tsk_isol_free(struct
 		__tsk_isol_free(tsk);
 }
 
+void __tsk_isol_exit(struct task_struct *tsk);
+static inline void tsk_isol_exit(struct task_struct *tsk)
+{
+	if (tsk->isol_info)
+		__tsk_isol_exit(tsk);
+}
+
 int prctl_task_isolation_feat_get(unsigned long arg2, unsigned long arg3,
 				  unsigned long arg4, unsigned long arg5);
 int prctl_task_isolation_cfg_get(unsigned long arg2, unsigned long arg3,
@@ -57,6 +64,10 @@ static inline void tsk_isol_free(struct
 {
 }
 
+static inline void tsk_isol_exit(struct task_struct *tsk)
+{
+}
+
 static inline int prctl_task_isolation_feat_get(unsigned long arg2,
 						unsigned long arg3,
 						unsigned long arg4,