[PATCH 3/9] mm: allow PF_MEMALLOC from softirq context

From: Peter Zijlstra
Date: Tue Jan 16 2007 - 05:31:56 EST


Allow PF_MEMALLOC to be set in softirq context. When running softirqs from
a borrowed context save current->flags, ksoftirqd will have its own
task_struct.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
kernel/softirq.c | 3 +++
mm/internal.h | 14 ++++++++------
2 files changed, 11 insertions(+), 6 deletions(-)

Index: linux-2.6-git/mm/internal.h
===================================================================
--- linux-2.6-git.orig/mm/internal.h 2006-12-14 10:02:52.000000000 +0100
+++ linux-2.6-git/mm/internal.h 2006-12-14 10:10:09.000000000 +0100
@@ -75,9 +75,10 @@ static int inline gfp_to_alloc_flags(gfp
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;
}

@@ -117,9 +118,10 @@ static inline int gfp_to_rank(gfp_t gfp_
*/

if (likely(!(gfp_mask & __GFP_NOMEMALLOC))) {
- if (!in_interrupt() &&
- ((current->flags & PF_MEMALLOC) ||
- unlikely(test_thread_flag(TIF_MEMDIE))))
+ if (!in_irq() && (current->flags & PF_MEMALLOC))
+ return 0;
+ else if (!in_interrupt() &&
+ unlikely(test_thread_flag(TIF_MEMDIE)))
return 0;
}

Index: linux-2.6-git/kernel/softirq.c
===================================================================
--- linux-2.6-git.orig/kernel/softirq.c 2006-12-14 10:02:18.000000000 +0100
+++ linux-2.6-git/kernel/softirq.c 2006-12-14 10:02:52.000000000 +0100
@@ -209,6 +209,8 @@ 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);
@@ -247,6 +249,7 @@ restart:

account_system_vtime(current);
_local_bh_enable();
+ current->flags = pflags;
}

#ifndef __ARCH_HAS_DO_SOFTIRQ

--

-
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