From: Naoya Horiguchi <nao.horiguchi@xxxxxxxxx> Subject: mm/memory-failure: prioritize prctl(PR_MCE_KILL) over vm.memory_failure_early_kill Patch series "hwpoison: fixes signaling on memory error" This is a small patchset to solve issues in memory error handler to send SIGBUS to proper process/thread as expected in configuration. Please see descriptions in individual patches for more details. This patch (of 2): Early-kill policy is controlled from two types of settings, one is per-process setting prctl(PR_MCE_KILL) and the other is system-wide setting vm.memory_failure_early_kill. Users expect per-process setting to override system-wide setting as many other settings do, but early-kill setting doesn't work as such. For example, if a system configures vm.memory_failure_early_kill to 1 (enabled), a process receives SIGBUS even if it's configured to explicitly disable PF_MCE_KILL by prctl(). That's not desirable for applications with their own policies. This patch is suggesting to change the priority of these two types of settings, by checking sysctl_memory_failure_early_kill only when a given process has the default kill policy. Note that this patch is solving a thread choice issue too. Originally, collect_procs() always chooses the main thread when vm.memory_failure_early_kill is 1, even if the process has a dedicated thread for memory error handling. SIGBUS should be sent to the dedicated thread if early-kill is enabled via vm.memory_failure_early_kill as we are doing for PR_MCE_KILL_EARLY processes. Link: http://lkml.kernel.org/r/1591321039-22141-1-git-send-email-naoya.horiguchi@xxxxxxx Link: http://lkml.kernel.org/r/1591321039-22141-2-git-send-email-naoya.horiguchi@xxxxxxx Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx> Cc: Tony Luck <tony.luck@xxxxxxxxx> Cc: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memory-failure.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) --- a/mm/memory-failure.c~mm-memory-failure-prioritize-prctlpr_mce_kill-over-vmmemory_failure_early_kill +++ a/mm/memory-failure.c @@ -402,9 +402,15 @@ static struct task_struct *find_early_ki { struct task_struct *t; - for_each_thread(tsk, t) - if ((t->flags & PF_MCE_PROCESS) && (t->flags & PF_MCE_EARLY)) - return t; + for_each_thread(tsk, t) { + if (t->flags & PF_MCE_PROCESS) { + if (t->flags & PF_MCE_EARLY) + return t; + } else { + if (sysctl_memory_failure_early_kill) + return t; + } + } return NULL; } @@ -417,17 +423,11 @@ static struct task_struct *find_early_ki static struct task_struct *task_early_kill(struct task_struct *tsk, int force_early) { - struct task_struct *t; if (!tsk->mm) return NULL; if (force_early) return tsk; - t = find_early_kill_thread(tsk); - if (t) - return t; - if (sysctl_memory_failure_early_kill) - return tsk; - return NULL; + return find_early_kill_thread(tsk); } /* _
