[PATCH 3.13 094/198] mm/memory-failure.c-failure: send right signal code to correct thread

From: Kamal Mostafa
Date: Tue Jul 15 2014 - 18:24:07 EST -stable review patch. If anyone has any objections, please let me know.


From: Tony Luck <tony.luck@xxxxxxxxx>

commit a70ffcac741d31a406c1d2b832ae43d658e7e1cf upstream.

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 <tony.luck@xxxxxxxxx>
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Reported-by: Otto Bruggeman <otto.g.bruggeman@xxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Chen Gong <gong.chen@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
mm/memory-failure.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 3b0855b..2b5da71 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -208,9 +208,9 @@ static int kill_proc(struct task_struct *t, unsigned long addr, int trapno,
si.si_addr_lsb = compound_order(compound_head(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

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