Re: [PATCH] -mm/linux-next: procfs: Mark thread stack correctly inproc/<pid>/maps

From: Andrew Morton
Date: Tue Mar 13 2012 - 16:16:18 EST

On Tue, 13 Mar 2012 23:04:36 +0530
Siddhesh Poyarekar <siddhesh.poyarekar@xxxxxxxxx> wrote:

> Following is the updated patch with requested changes incorporated.

Boy, that's a lot of changes (below). What does it all do?

Why did the sched.h inclusions get taken out again?


Documentation/filesystems/proc.txt | 36 +++++++++++++---
fs/proc/task_mmu.c | 59 ++++++++++++++++++---------
fs/proc/task_nommu.c | 11 ++++-
mm/memory.c | 38 -----------------
mm/nommu.c | 40 ------------------
mm/util.c | 41 ++++++++++++++++++
6 files changed, 121 insertions(+), 104 deletions(-)

diff -puN Documentation/filesystems/proc.txt~procfs-mark-thread-stack-correctly-in-proc-pid-maps-v3 Documentation/filesystems/proc.txt
--- a/Documentation/filesystems/proc.txt~procfs-mark-thread-stack-correctly-in-proc-pid-maps-v3
+++ a/Documentation/filesystems/proc.txt
@@ -325,7 +325,7 @@ address perms offset dev in
a7cb1000-a7cb2000 ---p 00000000 00:00 0
a7cb2000-a7eb2000 rw-p 00000000 00:00 0
a7eb2000-a7eb3000 ---p 00000000 00:00 0
-a7eb3000-a7ed5000 rw-p 00000000 00:00 0
+a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack:1001]
a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
@@ -337,7 +337,7 @@ a8024000-a8027000 rw-p 00000000 00:00 0
a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
-aff35000-aff4a000 rw-p 00000000 00:00 0 [stack:1001]
+aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]

where "address" is the address space in the process that it occupies, "perms"
@@ -356,8 +356,8 @@ The "pathname" shows the name associated
is not associated with a file:

[heap] = the heap of the program
- [stack:1001] = the mapping is used as a stack by the thread
- with tid 1001
+ [stack] = the stack of the main process
+ [stack:1001] = the stack of the thread with tid 1001
[vdso] = the "virtual dynamic shared object",
the kernel system call handler

@@ -365,9 +365,31 @@ is not associated with a file:

The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
of the individual tasks of a process. In this file you will see a mapping marked
-as [stack:TID] only if that task sees it as a stack. This is a key difference
-from the content of /proc/PID/maps, where you will see all mappings that are
-being used as stack by all of those tasks.
+as [stack] if that task sees it as a stack. This is a key difference from the
+content of /proc/PID/maps, where you will see all mappings that are being used
+as stack by all of those tasks. Hence, for the example above, the task-level
+map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:
+
+08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
+08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
+0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
+a7cb1000-a7cb2000 ---p 00000000 00:00 0
+a7cb2000-a7eb2000 rw-p 00000000 00:00 0
+a7eb2000-a7eb3000 ---p 00000000 00:00 0
+a7eb3000-a7ed5000 rw-p 00000000 00:00 0 [stack]
+a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
+a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
+a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
+a800b000-a800e000 rw-p 00000000 00:00 0
+a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
+a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
+a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
+a8024000-a8027000 rw-p 00000000 00:00 0
+a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
+a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
+a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
+aff35000-aff4a000 rw-p 00000000 00:00 0
+ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]

The /proc/PID/smaps is an extension based on maps, showing the memory
consumption for each of the process's mappings. For each of mappings there
diff -puN fs/proc/task_mmu.c~procfs-mark-thread-stack-correctly-in-proc-pid-maps-v3 fs/proc/task_mmu.c
--- a/fs/proc/task_mmu.c~procfs-mark-thread-stack-correctly-in-proc-pid-maps-v3
+++ a/fs/proc/task_mmu.c
@@ -222,7 +222,7 @@ show_map_vma(struct seq_file *m, struct
unsigned long start, end;
dev_t dev = 0;
int len;
- const char *name;
+ const char *name = NULL;

if (file) {
struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
@@ -256,33 +256,47 @@ show_map_vma(struct seq_file *m, struct
if (file) {
pad_len_spaces(m, len);
seq_path(m, &file->f_path, "\n");
- goto out;
+ goto done;
}

name = arch_vma_name(vma);
if (!name) {
- if (mm) {
- if (vma->vm_start <= mm->brk &&
- vma->vm_end >= mm->start_brk) {
- name = "[heap]";
- } else {
- pid_t tid;
+ pid_t tid;

- tid = vm_is_stack(task, vma, is_pid);
- if (tid != 0) {
- pad_len_spaces(m, len);
- seq_printf(m, "[stack:%d]", tid);
- }
- }
- } else {
+ if (!mm) {
name = "[vdso]";
+ goto done;
+ }
+
+ if (vma->vm_start <= mm->brk &&
+ vma->vm_end >= mm->start_brk) {
+ name = "[heap]";
+ goto done;
+ }
+
+ tid = vm_is_stack(task, vma, is_pid);
+
+ if (tid !=0) {
+ /*
+ * Thread stack in /proc/PID/task/TID/maps or
+ * the main process stack.
+ */
+ if (!is_pid || (vma->vm_start <= mm->start_stack &&
+ vma->vm_end >= mm->start_stack)) {
+ name = "[stack]";
+ } else {
+ /* Thread stack in /proc/PID/maps */
+ pad_len_spaces(m, len);
+ seq_printf(m, "[stack:%d]", tid);
+ }
}
}
+
+done:
if (name) {
pad_len_spaces(m, len);
seq_puts(m, name);
}
-out:
seq_putc(m, '\n');
}

@@ -1134,8 +1148,17 @@ static int show_numa_map(struct seq_file
seq_printf(m, " heap");
} else {
pid_t tid = vm_is_stack(proc_priv->task, vma, is_pid);
- if (tid != 0)
- seq_printf(m, " stack:%d", tid);
+ if (tid !=0) {
+ /*
+ * Thread stack in /proc/PID/task/TID/maps or
+ * the main process stack.
+ */
+ if (!is_pid || (vma->vm_start <= mm->start_stack &&
+ vma->vm_end >= mm->start_stack))
+ seq_printf(m, " stack");
+ else
+ seq_printf(m, " stack:%d", tid);
+ }
}

if (is_vm_hugetlb_page(vma))
diff -puN fs/proc/task_nommu.c~procfs-mark-thread-stack-correctly-in-proc-pid-maps-v3 fs/proc/task_nommu.c
--- a/fs/proc/task_nommu.c~procfs-mark-thread-stack-correctly-in-proc-pid-maps-v3
+++ a/fs/proc/task_nommu.c
@@ -171,9 +171,18 @@ static int nommu_vma_show(struct seq_fil
seq_path(m, &file->f_path, "");
} else if (mm) {
pid_t tid = vm_is_stack(priv->task, vma, is_pid);
+
if (tid != 0) {
pad_len_spaces(m, len);
- seq_printf(m, "[stack:%d]", tid);
+ /*
+ * Thread stack in /proc/PID/task/TID/maps or
+ * the main process stack.
+ */
+ if (!is_pid || (vma->vm_start <= mm->start_stack &&
+ vma->vm_end >= mm->start_stack))
+ seq_printf(m, "[stack]");
+ else
+ seq_printf(m, "[stack:%d]", tid);
}
}

diff -puN mm/memory.c~procfs-mark-thread-stack-correctly-in-proc-pid-maps-v3 mm/memory.c
--- a/mm/memory.c~procfs-mark-thread-stack-correctly-in-proc-pid-maps-v3
+++ a/mm/memory.c
@@ -57,7 +57,6 @@
#include <linux/swapops.h>
#include <linux/elf.h>
#include <linux/gfp.h>
-#include <linux/sched.h>

#include <asm/io.h>
#include <asm/pgalloc.h>
@@ -113,13 +112,6 @@ __setup("norandmaps", disable_randmaps);
unsigned long zero_pfn __read_mostly;
unsigned long highest_memmap_pfn __read_mostly;

-/* Check if the vma is being used as a stack by this task */
-static int vm_is_stack_for_task(struct task_struct *t,
- struct vm_area_struct *vma)
-{
- return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
-}
-
/*
* CONFIG_MMU architectures set up ZERO_PAGE in their paging_init()
*/
@@ -3899,36 +3891,6 @@ void print_vma_addr(char *prefix, unsign
up_read(&current->mm->mmap_sem);
}

-/*
- * Check if the vma is being used as a stack.
- * If is_group is non-zero, check in the entire thread group or else
- * just check in the current task. Returns the pid of the task that
- * the vma is stack for.
- */
-pid_t vm_is_stack(struct task_struct *task,
- struct vm_area_struct *vma, int in_group)
-{
- pid_t ret = 0;
-
- if (vm_is_stack_for_task(task, vma))
- return task->pid;
-
- if (in_group) {
- struct task_struct *t = task;
- rcu_read_lock();
- while_each_thread(task, t) {
- if (vm_is_stack_for_task(t, vma)) {
- ret = t->pid;
- goto done;
- }
- }
- }
-
-done:
- rcu_read_unlock();
- return ret;
-}
-
#ifdef CONFIG_PROVE_LOCKING
void might_fault(void)
{
diff -puN mm/nommu.c~procfs-mark-thread-stack-correctly-in-proc-pid-maps-v3 mm/nommu.c
--- a/mm/nommu.c~procfs-mark-thread-stack-correctly-in-proc-pid-maps-v3
+++ a/mm/nommu.c
@@ -29,7 +29,6 @@
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/audit.h>
-#include <linux/sched.h>

#include <asm/uaccess.h>
#include <asm/tlb.h>
@@ -2095,42 +2094,3 @@ int nommu_shrink_inode_mappings(struct i
up_write(&nommu_region_sem);
return 0;
}
-
-/* Check if the vma is being used as a stack by this task */
-static int vm_is_stack_for_task(struct task_struct *t,
- struct vm_area_struct *vma)
-{
- return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
-}
-
-/*
- * Check if the vma is being used as a stack.
- * If is_group is non-zero, check in the entire thread group or else
- * just check in the current task. Returns the pid of the task that
- * the vma is stack for.
- */
-pid_t vm_is_stack(struct task_struct *task,
- struct vm_area_struct *vma, int in_group)
-{
- pid_t ret = 0;
-
- if (vm_is_stack_for_task(task, vma))
- return task->pid;
-
- if (in_group) {
- struct task_struct *t;
- rcu_read_lock();
- t = list_first_entry_rcu(&task->thread_group,
- struct task_struct, thread_group);
- do {
- if (vm_is_stack_for_task(t, vma)) {
- ret = t->pid;
- goto done;
- }
- } while_each_thread(task, t);
-done:
- rcu_read_unlock();
- }
-
- return ret;
-}
diff -puN mm/util.c~procfs-mark-thread-stack-correctly-in-proc-pid-maps-v3 mm/util.c
--- a/mm/util.c~procfs-mark-thread-stack-correctly-in-proc-pid-maps-v3
+++ a/mm/util.c
@@ -239,6 +239,47 @@ void __vma_link_list(struct mm_struct *m
next->vm_prev = vma;
}

+/* Check if the vma is being used as a stack by this task */
+static int vm_is_stack_for_task(struct task_struct *t,
+ struct vm_area_struct *vma)
+{
+ return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
+}
+
+/*
+ * Check if the vma is being used as a stack.
+ * If is_group is non-zero, check in the entire thread group or else
+ * just check in the current task. Returns the pid of the task that
+ * the vma is stack for.
+ */
+pid_t vm_is_stack(struct task_struct *task,
+ struct vm_area_struct *vma, int in_group)
+{
+ pid_t ret = 0;
+
+ if (vm_is_stack_for_task(task, vma))
+ return task->pid;
+
+ if (in_group) {
+ struct task_struct *t;
+ rcu_read_lock();
+ if (!pid_alive(task))
+ goto done;
+
+ t = task;
+ do {
+ if (vm_is_stack_for_task(t, vma)) {
+ ret = t->pid;
+ goto done;
+ }
+ } while_each_thread(task, t);
+done:
+ rcu_read_unlock();
+ }
+
+ return ret;
+}
+
#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
void arch_pick_mmap_layout(struct mm_struct *mm)
{
_

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