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
