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Subject[patch] 2.4.13-pre3 arm/i386/mips/mips64/s390/s390x/sh die() deadlock
Date
Any die() routine that uses die_lock to avoid multiple cpu reentrancy
will deadlock on recursive die() errors. This patch only affects the
architectures that use die_lock and only if the code is in Linus's
tree.

I have not looked at the arch CVS trees so other architectures may
still have problems, please check. Several architectures have no
protection against multiple cpu reentrancy in die(), I left those
alone.

mips, mips64 and sh had uninitialized spinlock_t die_lock, naughty, it
breaks spin lock debugging. Any other uninitialized spinlock_t lying
around in those trees?

Most of the patch is white space changes due to new indentation.
Speaking of white space, s390/s390x has a lot of leading spaces instead
of tabs, did somebody code on an 026 card punch ;)? A white space
clean up on s390/s390x would be nice.

Patch against 2.4.13-pre3. Compiled on i386, eyeballed (using IEHIBALL
on s390) but untested on other arch.

Index: 13-pre3.1/arch/arm/kernel/traps.c
--- 13-pre3.1/arch/arm/kernel/traps.c Fri, 12 Oct 2001 11:40:38 +1000 kaos (linux-2.4/w/c/46_traps.c 1.3.1.2.1.1 644)
+++ 13-pre3.1(w)/arch/arm/kernel/traps.c Tue, 16 Oct 2001 12:03:28 +1000 kaos (linux-2.4/w/c/46_traps.c 1.3.1.2.1.1 644)
@@ -159,43 +159,49 @@ void show_trace_task(struct task_struct
}
}

-spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
-
-/*
- * This function is protected against re-entrancy.
- */
NORET_TYPE void die(const char *str, struct pt_regs *regs, int err)
{
+ static spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
+ static int die_lock_owner = -1, die_lock_owner_depth;
struct task_struct *tsk = current;

- console_verbose();
- spin_lock_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;
+ }

- printk("Internal error: %s: %x\n", str, err);
- printk("CPU: %d\n", smp_processor_id());
- show_regs(regs);
- printk("Process %s (pid: %d, stackpage=%08lx)\n",
- current->comm, current->pid, 4096+(unsigned long)tsk);
-
- if (!user_mode(regs) || in_interrupt()) {
- mm_segment_t fs;
-
- /*
- * We need to switch to kernel mode so that we can
- * use __get_user to safely read from kernel space.
- * Note that we now dump the code first, just in case
- * the backtrace kills us.
- */
- fs = get_fs();
- set_fs(KERNEL_DS);
-
- dump_stack(tsk, (unsigned long)(regs + 1));
- dump_backtrace(regs, tsk);
- dump_instr(regs);
+ if (++die_lock_owner_depth < 3) {
+ printk("Internal error: %s: %x\n", str, err);
+ printk("CPU: %d\n", smp_processor_id());
+ show_regs(regs);
+ printk("Process %s (pid: %d, stackpage=%08lx)\n",
+ current->comm, current->pid, 4096+(unsigned long)tsk);
+
+ if (!user_mode(regs) || in_interrupt()) {
+ mm_segment_t fs;
+
+ /*
+ * We need to switch to kernel mode so that we can
+ * use __get_user to safely read from kernel space.
+ * Note that we now dump the code first, just in case
+ * the backtrace kills us.
+ */
+ fs = get_fs();
+ set_fs(KERNEL_DS);
+
+ dump_stack(tsk, (unsigned long)(regs + 1));
+ dump_backtrace(regs, tsk);
+ dump_instr(regs);

- set_fs(fs);
+ set_fs(fs);
+ }
}
+ else
+ printk(KERN_ERR "Recursive die() failure, output suppressed\n");

+ die_lock_owner = -1;
spin_unlock_irq(&die_lock);
do_exit(SIGSEGV);
}
Index: 13-pre3.1/arch/i386/kernel/traps.c
--- 13-pre3.1/arch/i386/kernel/traps.c Tue, 02 Oct 2001 11:04:33 +1000 kaos (linux-2.4/S/c/22_traps.c 1.1.2.1.1.2.1.1.1.6 644)
+++ 13-pre3.1(w)/arch/i386/kernel/traps.c Tue, 16 Oct 2001 11:34:27 +1000 kaos (linux-2.4/S/c/22_traps.c 1.1.2.1.1.2.1.1.1.6 644)
@@ -237,16 +237,28 @@ bad:
printk("\n");
}

-spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
-
void die(const char * str, struct pt_regs * regs, long err)
{
- console_verbose();
- spin_lock_irq(&die_lock);
- bust_spinlocks(1);
- printk("%s: %04lx\n", str, err & 0xffff);
- show_registers(regs);
+ static spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
+ static int die_lock_owner = -1, die_lock_owner_depth;
+
+ 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 (++die_lock_owner_depth < 3) {
+ printk("%s: %04lx\n", str, err & 0xffff);
+ show_registers(regs);
+ }
+ 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: 13-pre3.1/arch/mips64/kernel/traps.c
--- 13-pre3.1/arch/mips64/kernel/traps.c Mon, 10 Sep 2001 15:46:51 +1000 kaos (linux-2.4/p/c/5_traps.c 1.1.1.1.1.1 644)
+++ 13-pre3.1(w)/arch/mips64/kernel/traps.c Tue, 16 Oct 2001 11:42:23 +1000 kaos (linux-2.4/p/c/5_traps.c 1.1.1.1.1.1 644)
@@ -159,23 +159,35 @@ void show_code(unsigned int *pc)
}
}

-spinlock_t die_lock;
-
void die(const char * str, struct pt_regs * regs, unsigned long err)
{
+ static spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
+ static int die_lock_owner = -1, die_lock_owner_depth;
+
if (user_mode(regs)) /* Just return if in user mode. */
return;

- console_verbose();
- spin_lock_irq(&die_lock);
- printk("%s: %04lx\n", str, err & 0xffff);
- show_regs(regs);
- printk("Process %s (pid: %d, stackpage=%08lx)\n",
- current->comm, current->pid, (unsigned long) current);
- show_stack((unsigned long *) regs->regs[29]);
- show_trace((unsigned long *) regs->regs[29]);
- show_code((unsigned int *) regs->cp0_epc);
- printk("\n");
+ 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;
+ }
+
+ if (++die_lock_owner_depth < 3) {
+ printk("%s: %04lx\n", str, err & 0xffff);
+ show_regs(regs);
+ printk("Process %s (pid: %d, stackpage=%08lx)\n",
+ current->comm, current->pid, (unsigned long) current);
+ show_stack((unsigned long *) regs->regs[29]);
+ show_trace((unsigned long *) regs->regs[29]);
+ show_code((unsigned int *) regs->cp0_epc);
+ printk("\n");
+ }
+ else
+ printk(KERN_ERR "Recursive die() failure, output suppressed\n");
+
+ die_lock_owner = -1;
spin_unlock_irq(&die_lock);
do_exit(SIGSEGV);
}
Index: 13-pre3.1/arch/mips/kernel/traps.c
--- 13-pre3.1/arch/mips/kernel/traps.c Mon, 10 Sep 2001 15:46:51 +1000 kaos (linux-2.4/M/c/26_traps.c 1.1.2.1.1.1.1.1 644)
+++ 13-pre3.1(w)/arch/mips/kernel/traps.c Tue, 16 Oct 2001 11:38:52 +1000 kaos (linux-2.4/M/c/26_traps.c 1.1.2.1.1.1.1.1 644)
@@ -188,24 +188,36 @@ void show_code(unsigned int *pc)
}
}

-spinlock_t die_lock;
-
extern void __die(const char * str, struct pt_regs * regs, const char *where,
unsigned long line)
{
- console_verbose();
- spin_lock_irq(&die_lock);
- printk("%s", str);
- if (where)
- printk(" in %s, line %ld", where, line);
- printk(":\n");
- show_regs(regs);
- printk("Process %s (pid: %d, stackpage=%08lx)\n",
- current->comm, current->pid, (unsigned long) current);
- show_stack((unsigned int *) regs->regs[29]);
- show_trace((unsigned int *) regs->regs[29]);
- show_code((unsigned int *) regs->cp0_epc);
- printk("\n");
+ static spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
+ static int die_lock_owner = -1, die_lock_owner_depth;
+
+ 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;
+ }
+
+ if (++die_lock_owner_depth < 3) {
+ printk("%s", str);
+ if (where)
+ printk(" in %s, line %ld", where, line);
+ printk(":\n");
+ show_regs(regs);
+ printk("Process %s (pid: %d, stackpage=%08lx)\n",
+ current->comm, current->pid, (unsigned long) current);
+ show_stack((unsigned int *) regs->regs[29]);
+ show_trace((unsigned int *) regs->regs[29]);
+ show_code((unsigned int *) regs->cp0_epc);
+ printk("\n");
+ }
+ else
+ printk(KERN_ERR "Recursive __die() failure, output suppressed\n");
+
+ die_lock_owner = -1;
spin_unlock_irq(&die_lock);
do_exit(SIGSEGV);
}
Index: 13-pre3.1/arch/s390/kernel/traps.c
--- 13-pre3.1/arch/s390/kernel/traps.c Fri, 12 Oct 2001 11:40:38 +1000 kaos (linux-2.4/n/c/8_traps.c 1.4.1.1 644)
+++ 13-pre3.1(w)/arch/s390/kernel/traps.c Tue, 16 Oct 2001 11:54:35 +1000 kaos (linux-2.4/n/c/8_traps.c 1.4.1.1 644)
@@ -60,18 +60,30 @@ extern void pfault_fini(void);
extern void pfault_interrupt(struct pt_regs *regs, __u16 error_code);
#endif

-spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
-
void die(const char * str, struct pt_regs * regs, long err)
{
- console_verbose();
- spin_lock_irq(&die_lock);
- bust_spinlocks(1);
- printk("%s: %04lx\n", str, err & 0xffff);
- show_regs(regs);
+ static spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
+ static int die_lock_owner = -1, die_lock_owner_depth;
+
+ 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 (++die_lock_owner_depth < 3) {
+ printk("%s: %04lx\n", str, err & 0xffff);
+ show_regs(regs);
+ }
+ else
+ printk(KERN_ERR "Recursive die() failure, output suppressed\n");
+
bust_spinlocks(0);
- spin_unlock_irq(&die_lock);
- do_exit(SIGSEGV);
+ die_lock_owner = -1;
+ spin_unlock_irq(&die_lock);
+ do_exit(SIGSEGV);
}

#define DO_ERROR(signr, str, name) \
Index: 13-pre3.1/arch/s390x/kernel/traps.c
--- 13-pre3.1/arch/s390x/kernel/traps.c Fri, 12 Oct 2001 11:40:38 +1000 kaos (linux-2.4/p/d/19_traps.c 1.2.1.1 644)
+++ 13-pre3.1(w)/arch/s390x/kernel/traps.c Tue, 16 Oct 2001 11:54:45 +1000 kaos (linux-2.4/p/d/19_traps.c 1.2.1.1 644)
@@ -58,18 +58,30 @@ extern void pfault_fini(void);
extern void pfault_interrupt(struct pt_regs *regs, __u16 error_code);
#endif

-spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
-
void die(const char * str, struct pt_regs * regs, long err)
{
- console_verbose();
- spin_lock_irq(&die_lock);
- bust_spinlocks(1);
- printk("%s: %04lx\n", str, err & 0xffff);
- show_regs(regs);
+ static spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
+ static int die_lock_owner = -1, die_lock_owner_depth;
+
+ 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 (++die_lock_owner_depth < 3) {
+ printk("%s: %04lx\n", str, err & 0xffff);
+ show_regs(regs);
+ }
+ else
+ printk(KERN_ERR "Recursive die() failure, output suppressed\n");
+
bust_spinlocks(0);
- spin_unlock_irq(&die_lock);
- do_exit(SIGSEGV);
+ die_lock_owner = -1;
+ spin_unlock_irq(&die_lock);
+ do_exit(SIGSEGV);
}

#define DO_ERROR(signr, str, name) \
Index: 13-pre3.1/arch/sh/kernel/traps.c
--- 13-pre3.1/arch/sh/kernel/traps.c Sun, 09 Sep 2001 19:22:07 +1000 kaos (linux-2.4/t/c/26_traps.c 1.4 644)
+++ 13-pre3.1(w)/arch/sh/kernel/traps.c Tue, 16 Oct 2001 11:51:17 +1000 kaos (linux-2.4/t/c/26_traps.c 1.4 644)
@@ -54,14 +54,26 @@ asmlinkage void do_##name(unsigned long
#define VMALLOC_OFFSET (8*1024*1024)
#define MODULE_RANGE (8*1024*1024)

-spinlock_t die_lock;
-
void die(const char * str, struct pt_regs * regs, long err)
{
- console_verbose();
- spin_lock_irq(&die_lock);
- printk("%s: %04lx\n", str, err & 0xffff);
- show_regs(regs);
+ static spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
+ static int die_lock_owner = -1, die_lock_owner_depth;
+
+ 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;
+ }
+
+ if (++die_lock_owner_depth < 3) {
+ printk("%s: %04lx\n", str, err & 0xffff);
+ show_regs(regs);
+ }
+ else
+ printk(KERN_ERR "Recursive die() failure, output suppressed\n");
+
+ die_lock_owner = -1;
spin_unlock_irq(&die_lock);
do_exit(SIGSEGV);
}
-
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