On Tue, May 20, 2014 at 09:28:00AM -0700, Tony Luck wrote:
> 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).
>
> Reported-by: Otto Bruggeman <otto.g.bruggeman@xxxxxxxxx>
> Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
Looks good to me, thank you.
Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
and I think this is worth going into stable trees.
Naoya
> ---
> 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 35ef28acf137..642c8434b166 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -204,9 +204,9 @@ static int kill_proc(struct task_struct *t, unsigned long addr, int trapno,
> #endif
> 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
> --
> 1.8.4.1
>
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