From cf52ebedba77ee494b495dedd3a1f55944611275 Mon Sep 17 00:00:00 2001 From: Neil Horman Date: Fri, 17 Oct 2008 17:00:13 -0400 Subject: [PATCH] x86, kexec: fix hang on i386 when panic occurs while console_sem is held There's 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. Patch below tested successfully by me. Signed-off-by: Neil Horman Signed-off-by: Ingo Molnar --- arch/x86/kernel/dumpstack_32.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c index 1a78180f08d..b3614752197 100644 --- a/arch/x86/kernel/dumpstack_32.c +++ b/arch/x86/kernel/dumpstack_32.c @@ -405,7 +405,6 @@ die_nmi(char *str, struct pt_regs *regs, int do_panic) 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, int do_panic) crash_kexec(regs); } + bust_spinlocks(0); do_exit(SIGSEGV); } -- 2.41.1