Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit d899bf7b authored by Stefani Seibold's avatar Stefani Seibold Committed by Linus Torvalds
Browse files

procfs: provide stack information for threads 



A patch to give a better overview of the userland application stack usage,
especially for embedded linux.

Currently you are only able to dump the main process/thread stack usage
which is showed in /proc/pid/status by the "VmStk" Value.  But you get no
information about the consumed stack memory of the the threads.

There is an enhancement in the /proc/<pid>/{task/*,}/*maps and which marks
the vm mapping where the thread stack pointer reside with "[thread stack
xxxxxxxx]".  xxxxxxxx is the maximum size of stack.  This is a value
information, because libpthread doesn't set the start of the stack to the
top of the mapped area, depending of the pthread usage.

A sample output of /proc/<pid>/task/<tid>/maps looks like:

08048000-08049000 r-xp 00000000 03:00 8312       /opt/z
08049000-0804a000 rw-p 00001000 03:00 8312       /opt/z
0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
a7d12000-a7d13000 ---p 00000000 00:00 0
a7d13000-a7f13000 rw-p 00000000 00:00 0          [thread stack: 001ff4b4]
a7f13000-a7f14000 ---p 00000000 00:00 0
a7f14000-a7f36000 rw-p 00000000 00:00 0
a7f36000-a8069000 r-xp 00000000 03:00 4222       /lib/libc.so.6
a8069000-a806b000 r--p 00133000 03:00 4222       /lib/libc.so.6
a806b000-a806c000 rw-p 00135000 03:00 4222       /lib/libc.so.6
a806c000-a806f000 rw-p 00000000 00:00 0
a806f000-a8083000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
a8083000-a8084000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
a8084000-a8085000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
a8085000-a8088000 rw-p 00000000 00:00 0
a8088000-a80a4000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
a80a4000-a80a5000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
a80a5000-a80a6000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
afaf5000-afb0a000 rw-p 00000000 00:00 0          [stack]
ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]

Also there is a new entry "stack usage" in /proc/<pid>/{task/*,}/status
which will you give the current stack usage in kb.

A sample output of /proc/self/status looks like:

Name:	cat
State:	R (running)
Tgid:	507
Pid:	507
.
.
.
CapBnd:	fffffffffffffeff
voluntary_ctxt_switches:	0
nonvoluntary_ctxt_switches:	0
Stack usage:	12 kB

I also fixed stack base address in /proc/<pid>/{task/*,}/stat to the base
address of the associated thread stack and not the one of the main
process.  This makes more sense.

[akpm@linux-foundation.org: fs/proc/array.c now needs walk_page_range()]
Signed-off-by: default avatarStefani Seibold <stefani@seibold.net>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent cba8aafe

Documentation/filesystems/proc.txt

+4 −1
Original line number Diff line number Diff line
@@ -176,6 +176,7 @@ read the file /proc/PID/status: 
  CapBnd: ffffffffffffffff

  voluntary_ctxt_switches:        0

  nonvoluntary_ctxt_switches:     1

  Stack usage:    12 kB



This shows you nearly the same information you would get if you viewed it with

the ps  command.  In  fact,  ps  uses  the  proc  file  system  to  obtain its
@@ -229,6 +230,7 @@ Table 1-2: Contents of the statm files (as of 2.6.30-rc7) 
 Mems_allowed_list           Same as previous, but in "list format"

 voluntary_ctxt_switches     number of voluntary context switches

 nonvoluntary_ctxt_switches  number of non voluntary context switches

 Stack usage:                stack usage high water mark (round up to page size)

..............................................................................



Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
@@ -307,7 +309,7 @@ address perms offset dev inode pathname 
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

a7cb2000-a7eb2000 rw-p 00000000 00:00 0          [threadstack:001ff4b4]

a7eb2000-a7eb3000 ---p 00000000 00:00 0

a7eb3000-a7ed5000 rw-p 00000000 00:00 0

a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
@@ -343,6 +345,7 @@ is not associated with a file: 
 [stack]                  = the stack of the main process

 [vdso]                   = the "virtual dynamic shared object",

                            the kernel system call handler

 [threadstack:xxxxxxxx]   = the stack of the thread, xxxxxxxx is the stack size



 or if empty, the mapping is anonymous.

fs/exec.c

+2 −0
Original line number Diff line number Diff line
@@ -1357,6 +1357,8 @@ int do_execve(char * filename, 
	if (retval < 0)

		goto out;



	current->stack_start = current->mm->start_stack;



	/* execve succeeded */

	current->fs->in_exec = 0;

	current->in_execve = 0;

fs/proc/array.c

+84 −1
Original line number Diff line number Diff line
@@ -82,6 +82,7 @@ 
#include <linux/pid_namespace.h>

#include <linux/ptrace.h>

#include <linux/tracehook.h>

#include <linux/swapops.h>



#include <asm/pgtable.h>

#include <asm/processor.h>
@@ -321,6 +322,87 @@ static inline void task_context_switch_counts(struct seq_file *m, 
			p->nivcsw);

}



struct stack_stats {

	struct vm_area_struct *vma;

	unsigned long	startpage;

	unsigned long	usage;

};



static int stack_usage_pte_range(pmd_t *pmd, unsigned long addr,

				unsigned long end, struct mm_walk *walk)

{

	struct stack_stats *ss = walk->private;

	struct vm_area_struct *vma = ss->vma;

	pte_t *pte, ptent;

	spinlock_t *ptl;

	int ret = 0;



	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);

	for (; addr != end; pte++, addr += PAGE_SIZE) {

		ptent = *pte;



#ifdef CONFIG_STACK_GROWSUP

		if (pte_present(ptent) || is_swap_pte(ptent))

			ss->usage = addr - ss->startpage + PAGE_SIZE;

#else

		if (pte_present(ptent) || is_swap_pte(ptent)) {

			ss->usage = ss->startpage - addr + PAGE_SIZE;

			pte++;

			ret = 1;

			break;

		}

#endif

	}

	pte_unmap_unlock(pte - 1, ptl);

	cond_resched();

	return ret;

}



static inline unsigned long get_stack_usage_in_bytes(struct vm_area_struct *vma,

				struct task_struct *task)

{

	struct stack_stats ss;

	struct mm_walk stack_walk = {

		.pmd_entry = stack_usage_pte_range,

		.mm = vma->vm_mm,

		.private = &ss,

	};



	if (!vma->vm_mm || is_vm_hugetlb_page(vma))

		return 0;



	ss.vma = vma;

	ss.startpage = task->stack_start & PAGE_MASK;

	ss.usage = 0;



#ifdef CONFIG_STACK_GROWSUP

	walk_page_range(KSTK_ESP(task) & PAGE_MASK, vma->vm_end,

		&stack_walk);

#else

	walk_page_range(vma->vm_start, (KSTK_ESP(task) & PAGE_MASK) + PAGE_SIZE,

		&stack_walk);

#endif

	return ss.usage;

}



static inline void task_show_stack_usage(struct seq_file *m,

						struct task_struct *task)

{

	struct vm_area_struct	*vma;

	struct mm_struct	*mm = get_task_mm(task);



	if (mm) {

		down_read(&mm->mmap_sem);

		vma = find_vma(mm, task->stack_start);

		if (vma)

			seq_printf(m, "Stack usage:\t%lu kB\n",

				get_stack_usage_in_bytes(vma, task) >> 10);



		up_read(&mm->mmap_sem);

		mmput(mm);

	}

}



int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,

			struct pid *pid, struct task_struct *task)

{
@@ -340,6 +422,7 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns, 
	task_show_regs(m, task);

#endif

	task_context_switch_counts(m, task);

	task_show_stack_usage(m, task);

	return 0;

}
@@ -481,7 +564,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, 
		rsslim,

		mm ? mm->start_code : 0,

		mm ? mm->end_code : 0,

		(permitted && mm) ? mm->start_stack : 0,

		(permitted) ? task->stack_start : 0,

		esp,

		eip,

		/* The signal information here is obsolete.

fs/proc/task_mmu.c

+19 −0
Original line number Diff line number Diff line
@@ -243,6 +243,25 @@ static void show_map_vma(struct seq_file *m, struct vm_area_struct *vma) 
				} else if (vma->vm_start <= mm->start_stack &&

					   vma->vm_end >= mm->start_stack) {

					name = "[stack]";

				} else {

					unsigned long stack_start;

					struct proc_maps_private *pmp;



					pmp = m->private;

					stack_start = pmp->task->stack_start;



					if (vma->vm_start <= stack_start &&

					    vma->vm_end >= stack_start) {

						pad_len_spaces(m, len);

						seq_printf(m,

						 "[threadstack:%08lx]",

#ifdef CONFIG_STACK_GROWSUP

						 vma->vm_end - stack_start

#else

						 stack_start - vma->vm_start

#endif

						);

					}

				}

			} else {

				name = "[vdso]";

include/linux/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -1529,6 +1529,7 @@ struct task_struct { 
	/* bitmask of trace recursion */

	unsigned long trace_recursion;

#endif /* CONFIG_TRACING */

	unsigned long stack_start;

};



/* Future-safe accessor for struct task_struct's cpus_allowed. */