[Linux-ia64] [patch] ia64-011010 die() deadlock

Keith Owens
2001-10-16T02:46:45Z

Any die() routine that uses die_lock to avoid multiple cpu reentrancy
will deadlock on recursive die() errors. This patch fixes ia64-011010.
Andrew Morton, who did the original die_lock code, agrees that this is
required.

The code makes best effort at diagnosing the first recursive error then
gives up. This patch removes the only reference to IA64_KERNEL_DEATH
so I deleted the flag as well.

Index: 11.7/arch/ia64/kernel/traps.c
--- 11.7/arch/ia64/kernel/traps.c Thu, 11 Oct 2001 14:03:29 +1000 kaos (linux-2.4/r/c/43_traps.c 1.1.4.1.3.4 644)
+++ 11.7(w)/arch/ia64/kernel/traps.c Tue, 16 Oct 2001 12:33:57 +1000 kaos (linux-2.4/r/c/43_traps.c 1.1.4.1.3.4 644)
@@ -88,21 +89,26 @@ void
die (const char *str, struct pt_regs *regs, long err)
{
static spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
+ static int die_lock_owner = -1, die_lock_owner_depth = 0;

- console_verbose();
- spin_lock_irq(&die_lock);
- bust_spinlocks(1);
- printk("%s[%d]: %s %ld\n", current->comm, current->pid, str, err);
- show_regs(regs);
- bust_spinlocks(0);
- spin_unlock_irq(&die_lock);
+ if (die_lock_owner != smp_processor_id()) {
+ console_verbose();
+ spin_lock_irq(&die_lock);
+ die_lock_owner = smp_processor_id();
+ die_lock_owner_depth = 0;
+ bust_spinlocks(1);
+ }

- if (current->thread.flags & IA64_KERNEL_DEATH) {
- printk("die_if_kernel recursion detected.\n");
- sti();
- while (1);
+ if (++die_lock_owner_depth < 3) {
+ printk("%s[%d]: %s %ld\n", current->comm, current->pid, str, err);
+ show_regs(regs);
}
- current->thread.flags |= IA64_KERNEL_DEATH;
+ else
+ printk(KERN_ERR "Recursive die() failure, output suppressed\n");
+
+ bust_spinlocks(0);
+ die_lock_owner = -1;
+ spin_unlock_irq(&die_lock);
do_exit(SIGSEGV);
}

Index: 11.7/include/asm-ia64/processor.h
--- 11.7/include/asm-ia64/processor.h Thu, 11 Oct 2001 14:03:29 +1000 kaos (linux-2.4/s/49_processor. 1.1.3.2.2.1.1.4 644)
+++ 11.7(w)/include/asm-ia64/processor.h Tue, 16 Oct 2001 12:28:13 +1000 kaos (linux-2.4/s/49_processor. 1.1.3.2.2.1.1.4 644)
@@ -170,7 +170,6 @@
#define IA64_THREAD_KRBS_SYNCED (__IA64_UL(1) << 5) /* krbs synced with process vm? */
#define IA64_THREAD_FPEMU_NOPRINT (__IA64_UL(1) << 6) /* don't log any fpswa faults */
#define IA64_THREAD_FPEMU_SIGFPE (__IA64_UL(1) << 7) /* send a SIGFPE for fpswa faults */
-#define IA64_KERNEL_DEATH (__IA64_UL(1) << 63) /* see die_if_kernel()... */

#define IA64_THREAD_UAC_SHIFT 3
#define IA64_THREAD_UAC_MASK (IA64_THREAD_UAC_NOPRINT | IA64_THREAD_UAC_SIGBUS)