From 94bce453c78996cc4373d5da6cfabe07fcc6d9f9 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Thu, 12 Sep 2013 15:13:36 -0700 Subject: arch: mm: remove obsolete init OOM protection The memcg code can trap tasks in the context of the failing allocation until an OOM situation is resolved. They can hold all kinds of locks (fs, mm) at this point, which makes it prone to deadlocking. This series converts memcg OOM handling into a two step process that is started in the charge context, but any waiting is done after the fault stack is fully unwound. Patches 1-4 prepare architecture handlers to support the new memcg requirements, but in doing so they also remove old cruft and unify out-of-memory behavior across architectures. Patch 5 disables the memcg OOM handling for syscalls, readahead, kernel faults, because they can gracefully unwind the stack with -ENOMEM. OOM handling is restricted to user triggered faults that have no other option. Patch 6 reworks memcg's hierarchical OOM locking to make it a little more obvious wth is going on in there: reduce locked regions, rename locking functions, reorder and document. Patch 7 implements the two-part OOM handling such that tasks are never trapped with the full charge stack in an OOM situation. This patch: Back before smart OOM killing, when faulting tasks were killed directly on allocation failures, the arch-specific fault handlers needed special protection for the init process. Now that all fault handlers call into the generic OOM killer (see commit 609838cfed97: "mm: invoke oom-killer from remaining unconverted page fault handlers"), which already provides init protection, the arch-specific leftovers can be removed. Signed-off-by: Johannes Weiner Reviewed-by: Michal Hocko Acked-by: KOSAKI Motohiro Cc: David Rientjes Cc: KAMEZAWA Hiroyuki Cc: azurIt Acked-by: Vineet Gupta [arch/arc bits] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/arc/mm/fault.c | 5 ----- 1 file changed, 5 deletions(-) (limited to 'arch/arc') diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c index 0fd1f0d515ff..6b0bb415af40 100644 --- a/arch/arc/mm/fault.c +++ b/arch/arc/mm/fault.c @@ -122,7 +122,6 @@ good_area: goto bad_area; } -survive: /* * If for any reason at all we couldn't handle the fault, * make sure we exit gracefully rather than endlessly redo @@ -201,10 +200,6 @@ no_context: die("Oops", regs, address); out_of_memory: - if (is_global_init(tsk)) { - yield(); - goto survive; - } up_read(&mm->mmap_sem); if (user_mode(regs)) { -- cgit v1.2.3 From 759496ba6407c6994d6a5ce3a5e74937d7816208 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Thu, 12 Sep 2013 15:13:39 -0700 Subject: arch: mm: pass userspace fault flag to generic fault handler Unlike global OOM handling, memory cgroup code will invoke the OOM killer in any OOM situation because it has no way of telling faults occuring in kernel context - which could be handled more gracefully - from user-triggered faults. Pass a flag that identifies faults originating in user space from the architecture-specific fault handlers to generic code so that memcg OOM handling can be improved. Signed-off-by: Johannes Weiner Reviewed-by: Michal Hocko Cc: David Rientjes Cc: KAMEZAWA Hiroyuki Cc: azurIt Cc: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/arc/mm/fault.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'arch/arc') diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c index 6b0bb415af40..d63f3de0cd5b 100644 --- a/arch/arc/mm/fault.c +++ b/arch/arc/mm/fault.c @@ -60,8 +60,7 @@ void do_page_fault(struct pt_regs *regs, unsigned long address) siginfo_t info; int fault, ret; int write = regs->ecr_cause & ECR_C_PROTV_STORE; /* ST/EX */ - unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE | - (write ? FAULT_FLAG_WRITE : 0); + unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; /* * We fault-in kernel-space virtual memory on-demand. The @@ -89,6 +88,8 @@ void do_page_fault(struct pt_regs *regs, unsigned long address) if (in_atomic() || !mm) goto no_context; + if (user_mode(regs)) + flags |= FAULT_FLAG_USER; retry: down_read(&mm->mmap_sem); vma = find_vma(mm, address); @@ -117,6 +118,7 @@ good_area: if (write) { if (!(vma->vm_flags & VM_WRITE)) goto bad_area; + flags |= FAULT_FLAG_WRITE; } else { if (!(vma->vm_flags & (VM_READ | VM_EXEC))) goto bad_area; -- cgit v1.2.3