From c4ac4263a019c791e906f284bb03891d3c25a845 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Sat, 25 Jun 2005 14:57:58 -0700 Subject: [PATCH] [PATCH] crashdump: x86: add NMI handler to capture other CPUs One of the dangers when switching from one kernel to another is what happens to all of the other cpus that were running in the crashed kernel. In an attempt to avoid that problem this patch adds a nmi handler and attempts to shoot down the other cpus by sending them non maskable interrupts. The code then waits for 1 second or until all known cpus have stopped running and then jumps from the running kernel that has crashed to the kernel in reserved memory. The kernel spin loop is used for the delay as that should behave continue to be safe even in after a crash. Signed-off-by: Eric Biederman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/crash.c | 56 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) diff --git a/arch/i386/kernel/crash.c b/arch/i386/kernel/crash.c index fa27a6c2abb..882779c0787 100644 --- a/arch/i386/kernel/crash.c +++ b/arch/i386/kernel/crash.c @@ -23,12 +23,65 @@ #include #include #include +#include #define MAX_NOTE_BYTES 1024 typedef u32 note_buf_t[MAX_NOTE_BYTES/4]; note_buf_t crash_notes[NR_CPUS]; +#ifdef CONFIG_SMP +static atomic_t waiting_for_crash_ipi; + +static int crash_nmi_callback(struct pt_regs *regs, int cpu) +{ + local_irq_disable(); + atomic_dec(&waiting_for_crash_ipi); + /* Assume hlt works */ + __asm__("hlt"); + for(;;); + return 1; +} + +/* + * By using the NMI code instead of a vector we just sneak thru the + * word generator coming out with just what we want. AND it does + * not matter if clustered_apic_mode is set or not. + */ +static void smp_send_nmi_allbutself(void) +{ + send_IPI_allbutself(APIC_DM_NMI); +} + +static void nmi_shootdown_cpus(void) +{ + unsigned long msecs; + atomic_set(&waiting_for_crash_ipi, num_online_cpus() - 1); + + /* Would it be better to replace the trap vector here? */ + set_nmi_callback(crash_nmi_callback); + /* Ensure the new callback function is set before sending + * out the NMI + */ + wmb(); + + smp_send_nmi_allbutself(); + + msecs = 1000; /* Wait at most a second for the other cpus to stop */ + while ((atomic_read(&waiting_for_crash_ipi) > 0) && msecs) { + mdelay(1); + msecs--; + } + + /* Leave the nmi callback set */ +} +#else +static void nmi_shootdown_cpus(void) +{ + /* There are no cpus to shootdown */ +} +#endif + void machine_crash_shutdown(void) { /* This function is only called after the system @@ -39,4 +92,7 @@ void machine_crash_shutdown(void) * In practice this means shooting down the other cpus in * an SMP system. */ + /* The kernel is broken so disable interrupts */ + local_irq_disable(); + nmi_shootdown_cpus(); } -- 2.41.1