revert "procfs: provide stack information for threads" and its fixup commits

commit 34441427aab4bdb3069a4ffcda69a99357abcb2e upstream.

Originally, commit d899bf7b ("procfs: provide stack information for
threads") attempted to introduce a new feature for showing where the
threadstack was located and how many pages are being utilized by the
stack.

Commit c44972f1 ("procfs: disable per-task stack usage on NOMMU") was
applied to fix the NO_MMU case.

Commit 89240ba0 ("x86, fs: Fix x86 procfs stack information for threads on
64-bit") was applied to fix a bug in ia32 executables being loaded.

Commit 9ebd4eba7 ("procfs: fix /proc/<pid>/stat stack pointer for kernel
threads") was applied to fix a bug which had kernel threads printing a
userland stack address.

Commit 1306d603f ('proc: partially revert "procfs: provide stack
information for threads"') was then applied to revert the stack pages
being used to solve a significant performance regression.

This patch nearly undoes the effect of all these patches.

The reason for reverting these is it provides an unusable value in
field 28.  For x86_64, a fork will result in the task->stack_start
value being updated to the current user top of stack and not the stack
start address.  This unpredictability of the stack_start value makes
it worthless.  That includes the intended use of showing how much stack
space a thread has.

Other architectures will get different values.  As an example, ia64
gets 0.  The do_fork() and copy_process() functions appear to treat the
stack_start and stack_size parameters as architecture specific.

I only partially reverted c44972f1 ("procfs: disable per-task stack usage
on NOMMU") .  If I had completely reverted it, I would have had to change
mm/Makefile only build pagewalk.o when CONFIG_PROC_PAGE_MONITOR is
configured.  Since I could not test the builds without significant effort,
I decided to not change mm/Makefile.

I only partially reverted 89240ba0 ("x86, fs: Fix x86 procfs stack
information for threads on 64-bit") .  I left the KSTK_ESP() change in
place as that seemed worthwhile.

Signed-off-by: Robin Holt <holt@sgi.com>
Cc: Stefani Seibold <stefani@seibold.net>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 58da9d9b72301a205bb1a0521c9dc5bd415ee88d..5c86fe95555ab468d044259d41b8cbd0a1d687ab 100644 (file)
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -307,7 +307,7 @@ 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          [threadstack:001ff4b4]
+a7cb2000-a7eb2000 rw-p 00000000 00:00 0
 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
@@ -343,7 +343,6 @@ 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.
 

diff --git a/fs/compat.c b/fs/compat.c
index 6c19040ffeefecdd520fc1093b5ed9db31e8aa7f..d576b552e8e2eb90a98324e79b7d8917fb96c04c 100644 (file)
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1532,8 +1532,6 @@ int compat_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;

diff --git a/fs/exec.c b/fs/exec.c
index a2a3944aab0dcb00529da382a4da645e55378c80..56da15f6d77100f5c604ba0eabb5df111e9379aa 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1379,8 +1379,6 @@ 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;

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 240787d2e99856279b7fc1cc03d3c9758981788e..725a650bbbb8bf3c1e90d1c84a6a7e1701f1ea96 100644 (file)
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -82,7 +82,6 @@
 #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>
@@ -482,7 +481,7 @@ 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) ? task->stack_start : 0,
+               (permitted && mm) ? mm->start_stack : 0,
                esp,
                eip,
                /* The signal information here is obsolete.

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 2a1bef9203c6e73734e7fa359873bbb45456d0ae..366b1017a4f13565287886cac1ed4077928319a5 100644 (file)
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -243,25 +243,6 @@ 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]";

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 70abfd3ee0aa463201e67ec3bf30e47600092ce0..b2534340748e4aaba645b257e5b3d3af315a850d 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1541,7 +1541,6 @@ 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. */

diff --git a/kernel/fork.c b/kernel/fork.c
index 166b8c49257c589750f0b67479011ba7bac97038..28b4874bff853bb48e63af6a34d80278ca07c6cc 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1123,8 +1123,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 
        p->bts = NULL;
 
-       p->stack_start = stack_start;
-
        /* Perform scheduler related setup. Assign this task to a CPU. */
        sched_fork(p, clone_flags);