Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932416AbZJAOEr (ORCPT ); Thu, 1 Oct 2009 10:04:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932256AbZJAOEp (ORCPT ); Thu, 1 Oct 2009 10:04:45 -0400 Received: from victor.provo.novell.com ([137.65.250.26]:53716 "EHLO victor.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932153AbZJAOEo (ORCPT ); Thu, 1 Oct 2009 10:04:44 -0400 From: Suresh Jayaraman To: Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: netdev@vger.kernel.org, Neil Brown , Miklos Szeredi , Wouter Verhelst , Peter Zijlstra , trond.myklebust@fys.uio.no, Suresh Jayaraman Subject: [PATCH 07/31] mm: allow PF_MEMALLOC from softirq context Date: Thu, 1 Oct 2009 19:35:56 +0530 Message-Id: <1254405956-15904-1-git-send-email-sjayaraman@suse.de> X-Mailer: git-send-email 1.6.0.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3277 Lines: 92 From: Peter Zijlstra This is needed to allow network softirq packet processing to make use of PF_MEMALLOC. Currently softirq context cannot use PF_MEMALLOC due to it not being associated with a task, and therefore not having task flags to fiddle with - thus the gfp to alloc flag mapping ignores the task flags when in interrupts (hard or soft) context. Allowing softirqs to make use of PF_MEMALLOC therefore requires some trickery. We basically borrow the task flags from whatever process happens to be preempted by the softirq. So we modify the gfp to alloc flags mapping to not exclude task flags in softirq context, and modify the softirq code to save, clear and restore the PF_MEMALLOC flag. The save and clear, ensures the preempted task's PF_MEMALLOC flag doesn't leak into the softirq. The restore ensures a softirq's PF_MEMALLOC flag cannot leak back into the preempted process. Signed-off-by: Peter Zijlstra Signed-off-by: Suresh Jayaraman --- include/linux/sched.h | 7 +++++++ kernel/softirq.c | 3 +++ mm/page_alloc.c | 7 ++++--- 3 files changed, 14 insertions(+), 3 deletions(-) Index: mmotm/include/linux/sched.h =================================================================== --- mmotm.orig/include/linux/sched.h +++ mmotm/include/linux/sched.h @@ -1724,6 +1724,13 @@ extern cputime_t task_gtime(struct task_ #define tsk_used_math(p) ((p)->flags & PF_USED_MATH) #define used_math() tsk_used_math(current) +static inline void tsk_restore_flags(struct task_struct *p, + unsigned long pflags, unsigned long mask) +{ + p->flags &= ~mask; + p->flags |= pflags & mask; +} + #ifdef CONFIG_SMP extern int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask); Index: mmotm/kernel/softirq.c =================================================================== --- mmotm.orig/kernel/softirq.c +++ mmotm/kernel/softirq.c @@ -194,6 +194,8 @@ asmlinkage void __do_softirq(void) __u32 pending; int max_restart = MAX_SOFTIRQ_RESTART; int cpu; + unsigned long pflags = current->flags; + current->flags &= ~PF_MEMALLOC; pending = local_softirq_pending(); account_system_vtime(current); @@ -246,6 +248,7 @@ restart: account_system_vtime(current); _local_bh_enable(); + tsk_restore_flags(current, pflags, PF_MEMALLOC); } #ifndef __ARCH_HAS_DO_SOFTIRQ Index: mmotm/mm/page_alloc.c =================================================================== --- mmotm.orig/mm/page_alloc.c +++ mmotm/mm/page_alloc.c @@ -1708,9 +1708,10 @@ int gfp_to_alloc_flags(gfp_t gfp_mask) alloc_flags |= ALLOC_HARDER; if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) { - if (!in_interrupt() && - ((p->flags & PF_MEMALLOC) || - unlikely(test_thread_flag(TIF_MEMDIE)))) + if (!in_irq() && (p->flags & PF_MEMALLOC)) + alloc_flags |= ALLOC_NO_WATERMARKS; + else if (!in_interrupt() && + unlikely(test_thread_flag(TIF_MEMDIE))) alloc_flags |= ALLOC_NO_WATERMARKS; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/