[Patch 13/21] Freeze / Thaw threads

[Suzuki K. Poulose]

All the threads in the target process are issued a freeze request on an "open()".
They are woken up when we release the fd.

Signed-off-by: Suzuki K. Poulose <suzuki@xxxxxxxxxx>
Signed-off-by: Ananth N.Mavinakayanahalli <ananth@xxxxxxxxxx>
---
 fs/proc/gencore.c |   26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

Index: linux-2.6.36-rc7/fs/proc/gencore.c
===================================================================
--- linux-2.6.36-rc7.orig/fs/proc/gencore.c
+++ linux-2.6.36-rc7/fs/proc/gencore.c
@@ -24,6 +24,7 @@
 
 #include <linux/seq_file.h>
 #include <linux/elf.h>
+#include <linux/freezer.h>
 
 #include "internal.h"
 #include "gencore.h"
@@ -70,11 +71,20 @@ out:
 static int release_gencore(struct inode *inode, struct file *file)
 {
 	struct task_struct *task = get_proc_task(file->f_dentry->d_inode);
+	struct task_struct *t;
 	struct core_proc *cp;
 
 	if (!task)
 		return -EIO;
 
+	/* Thaw all frozen threads */
+	t = task;
+	read_lock(&tasklist_lock);
+	do {
+		thaw_process(t);
+	} while ((t = next_thread(t)) != task);
+	read_unlock(&tasklist_lock);
+
 	mutex_lock(&core_mutex);
 	cp = get_core_proc(task);
 	if (cp) {
@@ -117,6 +127,7 @@ static int get_elf_class(struct task_str
 static int open_gencore(struct inode *inode, struct file *filp)
 {
 	struct task_struct *task = get_proc_task(inode);
+	struct task_struct *t;
 	struct core_proc *cp;
 	int ret = 0;
 	int elf_class;
@@ -148,6 +159,21 @@ static int open_gencore(struct inode *in
 	list_add(&cp->list, &core_list);
 	mutex_unlock(&core_mutex);
 
+	/* freeze the processes */
+	t = task;
+	read_lock(&tasklist_lock);
+	do {
+		if (frozen(t) || !freezeable(t) || freezing(t))
+			continue;
+
+		if (freeze_task(t, true))
+			continue;
+
+		if (task_is_stopped_or_traced(t))
+			continue;
+	} while ((t = next_thread(t)) != task);
+	read_unlock(&tasklist_lock);
+
 out:
 	put_task_struct(task);
 	return ret;
--
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