Il Mon, Oct 09, 2006 at 12:24:56AM +0200, Pavel Machek ha scritto:
> Hi!
>
> > > Could it be that the pm_ops->finish(SUSPEND_MEM) is somehow running
> > > asynchronously? And that something in the hardware forbids accessing
> > > certain
> > > memory regions while the AML code is still executed? Just wild guessing
> > > :-)
> > >
> > > Or asked the other way round:
> > > "What exactly is forbidden while all processes but the suspend program are
> > > frozen?"
> > > If we know what is forbidden, we might find out what we are doing wrong.
> > >
> > > Or: "What conditions can cause the kernel to kill a process with signal
> > > 11"?
> >
> > Since it's somewhat related to memory pressure: maybe (part of) the text
> > segment of either s2ram or glibc is evicted from memory or not yet
> > faulted in. Upon resume but before unfreeze() s2ram takes a page fault
> > but since no I/O can be started it just die. Make sense?
>
> No... it would hang waiting for disk to deliver the page...
Hum, pm_sem is held during suspension. Can this confuse the fault
handler? (I see that do_page_fault checks in_atomic(), but we are using
a sem so it shouldn't matter).
Stefan says that:
> it segfaults in the first glibc function used.
It happens on memory pressure, seems timing related, it looks like a
race... maybe something in the order in which kernel threads and
processes are unfrozen (shooting in the dark)?
Also (this may be a separate bug), when I added the S2RAM ioctl I used
the code in enter_state (kernel/power/main.c) as a reference; later
Linus added suspend_console (557240b48e2dc4f6fa878afc3fc767ad745ca7ed)
to the codepath used by /sys/power/state but not to the ioctl.
A printf may be involved so (again, shooting in the dark), what about
this one (against current git):
diff --git a/kernel/power/user.c b/kernel/power/user.c
index 93b5dd2..c5f329f 100644
--- a/kernel/power/user.c
+++ b/kernel/power/user.c
@@ -20,6 +20,7 @@ #include <linux/swapops.h>
#include <linux/pm.h>
#include <linux/fs.h>
#include <linux/cpu.h>
+#include <linux/console.h>
#include <asm/uaccess.h>
@@ -288,6 +289,7 @@ static int snapshot_ioctl(struct inode *
goto OutS3;
}
+ suspend_console();
/* Put devices to sleep */
error = device_suspend(PMSG_SUSPEND);
if (error) {
@@ -304,6 +306,7 @@ static int snapshot_ioctl(struct inode *
pm_ops->finish(PM_SUSPEND_MEM);
OutS3:
+ resume_console();
up(&pm_sem);
break;
>
> > Can you try this patch:
>
> ...but that patch makes lot of sense, anyway. I thought we did that,
> already?
Yeah, I was surprised too ;)
Luca
--
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