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

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Date:   Fri, 12 Nov 2021 09:16:47 -0300
From:   Marcelo Tosatti <mtosatti@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Nitesh Lal <nilal@...hat.com>,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Alex Belits <abelits@...its.com>, Peter Xu <peterx@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>
Subject: [patch v6 05/10] task isolation: add hook to task exit

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@...ora.localdomain>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8

Add task isolation specific hook to task exit routines.

Signed-off-by: Marcelo Tosatti <mtosatti@...hat.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/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,