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Message-Id: <201002040150.26503.rjw@sisk.pl>
Date: Thu, 4 Feb 2010 01:50:26 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Sebastian Ott <sebott@...ux.vnet.ibm.com>,
linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: [RFC][PATCH] PM: disable nonboot cpus before suspending devices
On Thursday 04 February 2010, Andrew Morton wrote:
> On Wed, 3 Feb 2010 23:34:37 +0100
> "Rafael J. Wysocki" <rjw@...k.pl> wrote:
>
> > On Wednesday 03 February 2010, Andrew Morton wrote:
> > > On Wed, 3 Feb 2010 02:44:23 +0100 "Rafael J. Wysocki" <rjw@...k.pl> wrote:
> > >
> > > > +static inline gfp_t clear_gfp_allowed_mask(gfp_t mask)
> > > > +{
> > > > + gfp_t ret = gfp_allowed_mask;
> > > > + gfp_allowed_mask &= ~mask;
> > > > + return ret;
> > > > +}
> > >
> > > Fair enuf.
> > >
> > > Of course, this is all horridly racy/buggy without locking. Would I be
> > > correct in hoping that all the callers happen when the system is in
> > > everyone-is-frozen mode?
> >
> > As far as I can tell, gfp_allowed_mask is only touched during init apart from
> > this.
>
> Well yes - the new interfaces are the problem - they're racy!
>
> > > Perhaps we should add some documentation (or even an assertion) to
> > > prevent someone from using these interfaces from within normal code.
> >
> > I thought about that, but didn't invent anything smart enough.
> >
> > Well, maybe except for a comment like "this must be called with pm_mutex held",
> > because that's the only case when it would be really safe.
>
> Is that the locking rule? My above guess was incorrect?
>
> Maybe slip a
>
> BUG_ON(!mutex_is_locked(&pm_mutex));
>
> in there?
That actually is a good idea, although I prefer WARN_ON (BUG_ON would be
rather blunt, so to speak, as it could kill setups not using suspend/hibernate
at all).
Updated patch follows.
Rafael
---
From: Rafael J. Wysocki <rjw@...k.pl>
Subject: MM / PM: Force GFP_NOIO during suspend/hibernation and resume (rev. 3)
There are quite a few GFP_KERNEL memory allocations made during
suspend/hibernation and resume that may cause the system to hang,
because the I/O operations they depend on cannot be completed due to
the underlying devices being suspended.
Mitigate this problem by clearing the __GFP_IO and __GFP_FS bits in
gfp_allowed_mask before suspend/hibernation and restoring the
original values of these bits in gfp_allowed_mask durig the
subsequent resume.
Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
Reported-by: Maxim Levitsky <maximlevitsky@...il.com>
---
include/linux/gfp.h | 7 +++----
init/main.c | 2 +-
kernel/power/hibernate.c | 9 +++++++++
kernel/power/suspend.c | 3 +++
mm/page_alloc.c | 24 ++++++++++++++++++++++++
5 files changed, 40 insertions(+), 5 deletions(-)
Index: linux-2.6/include/linux/gfp.h
===================================================================
--- linux-2.6.orig/include/linux/gfp.h
+++ linux-2.6/include/linux/gfp.h
@@ -83,6 +83,7 @@ struct vm_area_struct;
#define GFP_HIGHUSER_MOVABLE (__GFP_WAIT | __GFP_IO | __GFP_FS | \
__GFP_HARDWALL | __GFP_HIGHMEM | \
__GFP_MOVABLE)
+#define GFP_IOFS (__GFP_IO | __GFP_FS)
#ifdef CONFIG_NUMA
#define GFP_THISNODE (__GFP_THISNODE | __GFP_NOWARN | __GFP_NORETRY)
@@ -337,9 +338,7 @@ void drain_local_pages(void *dummy);
extern gfp_t gfp_allowed_mask;
-static inline void set_gfp_allowed_mask(gfp_t mask)
-{
- gfp_allowed_mask = mask;
-}
+extern void set_gfp_allowed_mask(gfp_t mask);
+extern gfp_t clear_gfp_allowed_mask(gfp_t mask);
#endif /* __LINUX_GFP_H */
Index: linux-2.6/init/main.c
===================================================================
--- linux-2.6.orig/init/main.c
+++ linux-2.6/init/main.c
@@ -601,7 +601,7 @@ asmlinkage void __init start_kernel(void
local_irq_enable();
/* Interrupts are enabled now so all GFP allocations are safe. */
- set_gfp_allowed_mask(__GFP_BITS_MASK);
+ gfp_allowed_mask = __GFP_BITS_MASK;
kmem_cache_init_late();
Index: linux-2.6/mm/page_alloc.c
===================================================================
--- linux-2.6.orig/mm/page_alloc.c
+++ linux-2.6/mm/page_alloc.c
@@ -76,6 +76,30 @@ unsigned long totalreserve_pages __read_
int percpu_pagelist_fraction;
gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK;
+/*
+ * The following functions are used by the suspend/hibernate code to temporarily
+ * change gfp_allowed_mask in order to avoid using I/O during memory allocations
+ * while devices are suspended. To avoid races with the suspend/hibernate code,
+ * they should always be called with pm_mutex held (gfp_allowed_mask also should
+ * only be modified with pm_mutex held, unless the suspend/hibernate code is
+ * guaranteed not to run in parallel with that modification).
+ */
+
+void set_gfp_allowed_mask(gfp_t mask)
+{
+ WARN_ON(!mutex_is_locked(&pm_mutex));
+ gfp_allowed_mask = mask;
+}
+
+gfp_t clear_gfp_allowed_mask(gfp_t mask)
+{
+ gfp_t ret = gfp_allowed_mask;
+
+ WARN_ON(!mutex_is_locked(&pm_mutex));
+ gfp_allowed_mask &= ~mask;
+ return ret;
+}
+
#ifdef CONFIG_HUGETLB_PAGE_SIZE_VARIABLE
int pageblock_order __read_mostly;
#endif
Index: linux-2.6/kernel/power/hibernate.c
===================================================================
--- linux-2.6.orig/kernel/power/hibernate.c
+++ linux-2.6/kernel/power/hibernate.c
@@ -323,6 +323,7 @@ static int create_image(int platform_mod
int hibernation_snapshot(int platform_mode)
{
int error;
+ gfp_t saved_mask;
error = platform_begin(platform_mode);
if (error)
@@ -334,6 +335,7 @@ int hibernation_snapshot(int platform_mo
goto Close;
suspend_console();
+ saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
error = dpm_suspend_start(PMSG_FREEZE);
if (error)
goto Recover_platform;
@@ -351,6 +353,7 @@ int hibernation_snapshot(int platform_mo
dpm_resume_end(in_suspend ?
(error ? PMSG_RECOVER : PMSG_THAW) : PMSG_RESTORE);
+ set_gfp_allowed_mask(saved_mask);
resume_console();
Close:
platform_end(platform_mode);
@@ -445,14 +448,17 @@ static int resume_target_kernel(bool pla
int hibernation_restore(int platform_mode)
{
int error;
+ gfp_t saved_mask;
pm_prepare_console();
suspend_console();
+ saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
error = dpm_suspend_start(PMSG_QUIESCE);
if (!error) {
error = resume_target_kernel(platform_mode);
dpm_resume_end(PMSG_RECOVER);
}
+ set_gfp_allowed_mask(saved_mask);
resume_console();
pm_restore_console();
return error;
@@ -466,6 +472,7 @@ int hibernation_restore(int platform_mod
int hibernation_platform_enter(void)
{
int error;
+ gfp_t saved_mask;
if (!hibernation_ops)
return -ENOSYS;
@@ -481,6 +488,7 @@ int hibernation_platform_enter(void)
entering_platform_hibernation = true;
suspend_console();
+ saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
error = dpm_suspend_start(PMSG_HIBERNATE);
if (error) {
if (hibernation_ops->recover)
@@ -518,6 +526,7 @@ int hibernation_platform_enter(void)
Resume_devices:
entering_platform_hibernation = false;
dpm_resume_end(PMSG_RESTORE);
+ set_gfp_allowed_mask(saved_mask);
resume_console();
Close:
Index: linux-2.6/kernel/power/suspend.c
===================================================================
--- linux-2.6.orig/kernel/power/suspend.c
+++ linux-2.6/kernel/power/suspend.c
@@ -198,6 +198,7 @@ static int suspend_enter(suspend_state_t
int suspend_devices_and_enter(suspend_state_t state)
{
int error;
+ gfp_t saved_mask;
if (!suspend_ops)
return -ENOSYS;
@@ -208,6 +209,7 @@ int suspend_devices_and_enter(suspend_st
goto Close;
}
suspend_console();
+ saved_mask = clear_gfp_allowed_mask(GFP_IOFS);
suspend_test_start();
error = dpm_suspend_start(PMSG_SUSPEND);
if (error) {
@@ -224,6 +226,7 @@ int suspend_devices_and_enter(suspend_st
suspend_test_start();
dpm_resume_end(PMSG_RESUME);
suspend_test_finish("resume devices");
+ set_gfp_allowed_mask(saved_mask);
resume_console();
Close:
if (suspend_ops->end)
--
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