The s390 architecture uses the task pid to tag the samples stored
by the sampling facility. The user space tool can use the tag to
distinguish the samples of different tasks. The pid is announced
to the sampling facility with the LPP instruction, the update of
the tag is done in __switch_to().
In a multi-threaded program any thread can call execve(). If this
is not done by the thread group leader, the de_thread() function
replaces the pid of the task that calls execve() with the pid of
thread group leader. If the task reaches user space again without
going over __switch_to() the sampling tag is still set to the old
pid.
Add the arch_change_pid function to re-issue the LPP to set the
new pid for the task in case of a thread ground leader change.
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
---
arch/s390/include/asm/thread_info.h | 2 ++
arch/s390/kernel/process.c | 10 ++++++++++
kernel/pid.c | 5 +++++
3 files changed, 17 insertions(+)
diff --git a/arch/s390/include/asm/thread_info.h b/arch/s390/include/asm/thread_info.h
index 83ba575..6f99b2f 100644
--- a/arch/s390/include/asm/thread_info.h
+++ b/arch/s390/include/asm/thread_info.h
@@ -42,6 +42,8 @@ struct thread_info {
.flags = 0, \
}
+enum pid_type;
+void arch_change_pid(struct task_struct *task, enum pid_type type);
void arch_release_task_struct(struct task_struct *tsk);
int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src);
diff --git a/arch/s390/kernel/process.c b/arch/s390/kernel/process.c
index 70576a2..1a716e7 100644
--- a/arch/s390/kernel/process.c
+++ b/arch/s390/kernel/process.c
@@ -29,6 +29,7 @@
#include <linux/random.h>
#include <linux/export.h>
#include <linux/init_task.h>
+#include <asm/cpu_mf.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/vtimer.h>
@@ -68,6 +69,15 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
return 0;
}
+void arch_change_pid(struct task_struct *task, enum pid_type type)
+{
+ if (type == PIDTYPE_PID && task == current) {
+ S390_lowcore.current_pid = current->pid;
+ if (test_facility(40))
+ lpp(&S390_lowcore.lpp);
+ }
+}
+
int copy_thread_tls(unsigned long clone_flags, unsigned long new_stackp,
unsigned long arg, struct task_struct *p, unsigned long tls)
{
diff --git a/kernel/pid.c b/kernel/pid.c
index 157fe4b..d38ac18 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -299,11 +299,16 @@ void detach_pid(struct task_struct *task, enum pid_type type)
__change_pid(task, type, NULL);
}
+void __weak arch_change_pid(struct task_struct *task, enum pid_type type)
+{
+}
+
void change_pid(struct task_struct *task, enum pid_type type,
struct pid *pid)
{
__change_pid(task, type, pid);
attach_pid(task, type);
+ arch_change_pid(task, type);
}
/* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */
--
2.7.4
