The patch titled
kexec: fix hang on i386 when panic occurs while console_sem is held
has been added to the -mm tree. Its filename is
kexec-fix-hang-on-i386-when-panic-occurs-while-console_sem-is-held.patch
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Subject: kexec: fix hang on i386 when panic occurs while console_sem is held
From: Neil Horman <nhorman@xxxxxxxxxxxxx>
There is a corner case in 32 bit x86 kdump at the moment. When the box
panics via nmi, we call bust_spinlocks(1) to disable sensitivity to the
console_sem (allowing us to print to the console in all cases), but we don't
call crash_kexec, until after we call bust_spinlocks(0), which re-enables
console_sem sensitivity.
The result is that, if we get an nmi while the console_sem is held and
kdump is configured, and we try to print something to the console during
kdump shutdown (which we often do) we deadlock the box. The fix is to
simply do what 64 bit die_nmi does which is to not call bust_spinlocks(0)
until after we call crash_kexec.
Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/dumpstack_32.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN arch/x86/kernel/dumpstack_32.c~kexec-fix-hang-on-i386-when-panic-occurs-while-console_sem-is-held arch/x86/kernel/dumpstack_32.c
--- a/arch/x86/kernel/dumpstack_32.c~kexec-fix-hang-on-i386-when-panic-occurs-while-console_sem-is-held
+++ a/arch/x86/kernel/dumpstack_32.c
@@ -405,7 +405,6 @@ die_nmi(char *str, struct pt_regs *regs,
panic("Non maskable interrupt");
console_silent();
spin_unlock(&nmi_print_lock);
- bust_spinlocks(0);
/*
* If we are in kernel we are probably nested up pretty bad
@@ -416,6 +415,7 @@ die_nmi(char *str, struct pt_regs *regs,
crash_kexec(regs);
}
+ bust_spinlocks(0);
do_exit(SIGSEGV);
}
_
Patches currently in -mm which might be from nhorman@xxxxxxxxxxxxx are
origin.patch
linux-next.patch
kexec-fix-hang-on-i386-when-panic-occurs-while-console_sem-is-held.patch
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