The patch titled Subject: powerpc: use clear_tasks_mm_cpumask() has been removed from the -mm tree. Its filename was powerpc-use-clear_tasks_mm_cpumask.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ From: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx> Subject: powerpc: use clear_tasks_mm_cpumask() Current CPU hotplug code has some task->mm handling issues: 1. Working with task->mm w/o getting mm or grabing the task lock is dangerous as ->mm might disappear (exit_mm() assigns NULL under task_lock(), so tasklist lock is not enough). We can't use get_task_mm()/mmput() pair as mmput() might sleep, so we must take the task lock while handle its mm. 2. Checking for process->mm is not enough because process' main thread may exit or detach its mm via use_mm(), but other threads may still have a valid mm. To fix this we would need to use find_lock_task_mm(), which would walk up all threads and returns an appropriate task (with task lock held). clear_tasks_mm_cpumask() has all the issues fixed, so let's use it. Suggested-by: Oleg Nesterov <oleg@xxxxxxxxxx> Signed-off-by: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx> Acked-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/powerpc/mm/mmu_context_nohash.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) diff -puN arch/powerpc/mm/mmu_context_nohash.c~powerpc-use-clear_tasks_mm_cpumask arch/powerpc/mm/mmu_context_nohash.c --- a/arch/powerpc/mm/mmu_context_nohash.c~powerpc-use-clear_tasks_mm_cpumask +++ a/arch/powerpc/mm/mmu_context_nohash.c @@ -333,9 +333,7 @@ static int __cpuinit mmu_context_cpu_not unsigned long action, void *hcpu) { unsigned int cpu = (unsigned int)(long)hcpu; -#ifdef CONFIG_HOTPLUG_CPU - struct task_struct *p; -#endif + /* We don't touch CPU 0 map, it's allocated at aboot and kept * around forever */ @@ -358,12 +356,7 @@ static int __cpuinit mmu_context_cpu_not stale_map[cpu] = NULL; /* We also clear the cpu_vm_mask bits of CPUs going away */ - read_lock(&tasklist_lock); - for_each_process(p) { - if (p->mm) - cpumask_clear_cpu(cpu, mm_cpumask(p->mm)); - } - read_unlock(&tasklist_lock); + clear_tasks_mm_cpumask(cpu); break; #endif /* CONFIG_HOTPLUG_CPU */ } _ Patches currently in -mm which might be from anton.vorontsov@xxxxxxxxxx are origin.patch sh-use-clear_tasks_mm_cpumask.patch blackfin-a-couple-of-task-mm-handling-fixes.patch blackfin-fix-possible-deadlock-in-decode_address.patch um-should-hold-tasklist_lock-while-traversing-processes.patch um-fix-possible-race-on-task-mm.patch um-properly-check-all-process-threads-for-a-live-mm.patch kernel-cpuc-document-clear_tasks_mm_cpumask.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html