Subject: + memory-failure-send-right-signal-code-to-correct-thread.patch added 
to -mm tree
To: 
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected]
From: [email protected]
Date: Mon, 02 Jun 2014 15:45:12 -0700


The patch titled
     Subject: mm/memory-failure.c-failure: send right signal code to correct 
thread
has been added to the -mm tree.  Its filename is
     memory-failure-send-right-signal-code-to-correct-thread.patch

This patch should soon appear at
    
http://ozlabs.org/~akpm/mmots/broken-out/memory-failure-send-right-signal-code-to-correct-thread.patch
and later at
    
http://ozlabs.org/~akpm/mmotm/broken-out/memory-failure-send-right-signal-code-to-correct-thread.patch

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------------------------------------------------------
From: Tony Luck <[email protected]>
Subject: mm/memory-failure.c-failure: send right signal code to correct thread

When a thread in a multi-threaded application hits a machine check because
of an uncorrectable error in memory - we want to send the SIGBUS with
si.si_code = BUS_MCEERR_AR to that thread.  Currently we fail to do that
if the active thread is not the primary thread in the process. 
collect_procs() just finds primary threads and this test:

        if ((flags & MF_ACTION_REQUIRED) && t == current) {

will see that the thread we found isn't the current thread and so send a
si.si_code = BUS_MCEERR_AO to the primary (and nothing to the active
thread at this time).

We can fix this by checking whether "current" shares the same mm with the
process that collect_procs() said owned the page.  If so, we send the
SIGBUS to current (with code BUS_MCEERR_AR).

Signed-off-by: Tony Luck <[email protected]>
Signed-off-by: Naoya Horiguchi <[email protected]>
Reported-by: Otto Bruggeman <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Chen Gong <[email protected]>
Cc: <[email protected]>    [3.2+]
Signed-off-by: Andrew Morton <[email protected]>
---

 mm/memory-failure.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff -puN 
mm/memory-failure.c~memory-failure-send-right-signal-code-to-correct-thread 
mm/memory-failure.c
--- 
a/mm/memory-failure.c~memory-failure-send-right-signal-code-to-correct-thread
+++ a/mm/memory-failure.c
@@ -204,9 +204,9 @@ static int kill_proc(struct task_struct
 #endif
        si.si_addr_lsb = page_size_order(page) + PAGE_SHIFT;
 
-       if ((flags & MF_ACTION_REQUIRED) && t == current) {
+       if ((flags & MF_ACTION_REQUIRED) && t->mm == current->mm) {
                si.si_code = BUS_MCEERR_AR;
-               ret = force_sig_info(SIGBUS, &si, t);
+               ret = force_sig_info(SIGBUS, &si, current);
        } else {
                /*
                 * Don't use force here, it's convenient if the signal
_

Patches currently in -mm which might be from [email protected] are

hugetlb-restrict-hugepage_migration_support-to-x86_64.patch
memory-failure-send-right-signal-code-to-correct-thread.patch
memory-failure-dont-let-collect_procs-skip-over-processes-for-mf_action_required.patch
mm-memory-failurec-support-dedicated-thread-to-handle-sigbusbus_mceerr_ao.patch
lib-scatterlist-make-arch_has_sg_chain-an-actual-kconfig.patch
lib-scatterlist-clean-up-useless-architecture-versions-of-scatterlisth.patch
linux-next.patch

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