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authorRobin Holt <holt@sgi.com>2010-05-11 14:06:46 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-05-11 17:33:41 -0700
commit34441427aab4bdb3069a4ffcda69a99357abcb2e (patch)
tree3beebde910f25b0945e9105017fd743c9e5241a5 /Documentation
parent3c904afd7358e9ef515eb5df36b6f25c2b7fc2da (diff)
revert "procfs: provide stack information for threads" and its fixup commits
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> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/proc.txt3
1 files changed, 1 insertions, 2 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index a4f30faa4f1..1e359b62c40 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -316,7 +316,7 @@ 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
@@ -352,7 +352,6 @@ 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.