linux-kernel - [PATCH v2 6/6] um: Stop tracking host PID in cpu

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Date: Mon, 05 Feb 2024 19:47:08 +0800
From: "Tiwei Bie" <tiwei.btw@...group.com>
To: richard@....at,
	anton.ivanov@...bridgegreys.com,
	johannes@...solutions.net
Cc:  <linux-um@...ts.infradead.org>,
   <linux-kernel@...r.kernel.org>,
  "Tiwei Bie" <tiwei.btw@...group.com>
Subject: [PATCH v2 6/6] um: Stop tracking host PID in cpu_tasks

The host PID tracked in 'cpu_tasks' is no longer used. Stopping
tracking it will also save some cycles.

Signed-off-by: Tiwei Bie <tiwei.btw@...group.com>
---
 arch/um/include/shared/as-layout.h |  1 -
 arch/um/kernel/process.c           | 12 ++----------
 arch/um/kernel/skas/process.c      |  4 ----
 3 files changed, 2 insertions(+), 15 deletions(-)

diff --git a/arch/um/include/shared/as-layout.h b/arch/um/include/shared/as-layout.h
index 9ec3015bc5e2..c22f46a757dc 100644
--- a/arch/um/include/shared/as-layout.h
+++ b/arch/um/include/shared/as-layout.h
@@ -31,7 +31,6 @@
 #include <sysdep/ptrace.h>
 
 struct cpu_task {
-	int pid;
 	void *task;
 };
 
diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 4235e2ca2664..1201c1a79b23 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -43,13 +43,7 @@
  * cares about its entry, so it's OK if another processor is modifying its
  * entry.
  */
-struct cpu_task cpu_tasks[NR_CPUS] = { [0 ... NR_CPUS - 1] = { -1, NULL } };
-
-static inline int external_pid(void)
-{
-	/* FIXME: Need to look up userspace_pid by cpu */
-	return userspace_pid[0];
-}
+struct cpu_task cpu_tasks[NR_CPUS] = { [0 ... NR_CPUS - 1] = { NULL } };
 
 void free_stack(unsigned long stack, int order)
 {
@@ -70,8 +64,7 @@ unsigned long alloc_stack(int order, int atomic)
 
 static inline void set_current(struct task_struct *task)
 {
-	cpu_tasks[task_thread_info(task)->cpu] = ((struct cpu_task)
-		{ external_pid(), task });
+	cpu_tasks[task_thread_info(task)->cpu] = ((struct cpu_task) { task });
 }
 
 extern void arch_switch_to(struct task_struct *to);
@@ -208,7 +201,6 @@ void um_idle_sleep(void)
 
 void arch_cpu_idle(void)
 {
-	cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
 	um_idle_sleep();
 }
 
diff --git a/arch/um/kernel/skas/process.c b/arch/um/kernel/skas/process.c
index fdd5922f9222..99a5cbb36083 100644
--- a/arch/um/kernel/skas/process.c
+++ b/arch/um/kernel/skas/process.c
@@ -18,12 +18,8 @@ extern void start_kernel(void);
 
 static int __init start_kernel_proc(void *unused)
 {
-	int pid;
-
 	block_signals_trace();
-	pid = os_getpid();
 
-	cpu_tasks[0].pid = pid;
 	cpu_tasks[0].task = current;
 
 	start_kernel();
-- 
2.34.1