1 files changed, 64 insertions, 0 deletions

diff --git a/recipes-kernel/linux/linux-ti33x-psp-3.2/3.2.2/0124-proc-clear_refs-do-not-clear-reserved-pages.patch b/recipes-kernel/linux/linux-ti33x-psp-3.2/3.2.2/0124-proc-clear_refs-do-not-clear-reserved-pages.patch
new file mode 100644
index 00000000..c27ca944
--- /dev/null
+++ b/recipes-kernel/linux/linux-ti33x-psp-3.2/3.2.2/0124-proc-clear_refs-do-not-clear-reserved-pages.patch
@@ -0,0 +1,64 @@
+From 6568c3dad4c19c7cfbd948fbf3f4935f0ab8d0ef Mon Sep 17 00:00:00 2001
+From: Will Deacon <will.deacon@arm.com>
+Date: Fri, 20 Jan 2012 14:34:09 -0800
+Subject: [PATCH 124/130] proc: clear_refs: do not clear reserved pages
+
+commit 85e72aa5384b1a614563ad63257ded0e91d1a620 upstream.
+
+/proc/pid/clear_refs is used to clear the Referenced and YOUNG bits for
+pages and corresponding page table entries of the task with PID pid, which
+includes any special mappings inserted into the page tables in order to
+provide things like vDSOs and user helper functions.
+
+On ARM this causes a problem because the vectors page is mapped as a
+global mapping and since ec706dab ("ARM: add a vma entry for the user
+accessible vector page"), a VMA is also inserted into each task for this
+page to aid unwinding through signals and syscall restarts.  Since the
+vectors page is required for handling faults, clearing the YOUNG bit (and
+subsequently writing a faulting pte) means that we lose the vectors page
+*globally* and cannot fault it back in.  This results in a system deadlock
+on the next exception.
+
+To see this problem in action, just run:
+
+        $ echo 1 > /proc/self/clear_refs
+
+on an ARM platform (as any user) and watch your system hang.  I think this
+has been the case since 2.6.37
+
+This patch avoids clearing the aforementioned bits for reserved pages,
+therefore leaving the vectors page intact on ARM.  Since reserved pages
+are not candidates for swap, this change should not have any impact on the
+usefulness of clear_refs.
+
+Signed-off-by: Will Deacon <will.deacon@arm.com>
+Reported-by: Moussa Ba <moussaba@micron.com>
+Acked-by: Hugh Dickins <hughd@google.com>
+Cc: David Rientjes <rientjes@google.com>
+Cc: Russell King <rmk@arm.linux.org.uk>
+Acked-by: Nicolas Pitre <nico@linaro.org>
+Cc: Matt Mackall <mpm@selenic.com>
+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>
+---
+ fs/proc/task_mmu.c |    3 +++
+ 1 files changed, 3 insertions(+), 0 deletions(-)
+
+diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
+index e418c5a..7dcd2a2 100644
+--- a/fs/proc/task_mmu.c
++++ b/fs/proc/task_mmu.c
+@@ -518,6 +518,9 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
+                if (!page)
+                        continue;
+ 
++               if (PageReserved(page))
++                       continue;
++
+                /* Clear accessed and referenced bits. */
+                ptep_test_and_clear_young(vma, addr, pte);
+                ClearPageReferenced(page);
+-- 
+1.7.7.4
+