From 02df19b4227e5b799e4642e88b568f9474fa78d0 Mon Sep 17 00:00:00 2001 From: Rabin Vincent Date: Fri, 15 Jun 2012 10:23:32 +0100 Subject: [PATCH] ARM: 7424/1: update die handler from x86 Robustify ARM's die() handling with improvements from x86: - Fix for a deadlock (before panic in the case of panic_on_oops) if we oops under a spinlock which is also used from interrupt handler, since the old code was unconditionally enabling interrupts. - Usage of arch spinlock so lockdep etc doesn't get involved while we're trying to dump out oopses. - Deadlock prevention in the unlikely event that die() recurses. The changes all touch the same few lines of code, so they're done together in one patch. Signed-off-by: Rabin Vincent Signed-off-by: Russell King --- arch/arm/kernel/traps.c | 78 +++++++++++++++++++++++++++++------------ 1 file changed, 55 insertions(+), 23 deletions(-) diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c index 4928d89758f4..2df8715c36c0 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -233,9 +233,9 @@ void show_stack(struct task_struct *tsk, unsigned long *sp) #define S_ISA " ARM" #endif -static int __die(const char *str, int err, struct thread_info *thread, struct pt_regs *regs) +static int __die(const char *str, int err, struct pt_regs *regs) { - struct task_struct *tsk = thread->task; + struct task_struct *tsk = current; static int die_counter; int ret; @@ -245,12 +245,12 @@ static int __die(const char *str, int err, struct thread_info *thread, struct pt /* trap and error numbers are mostly meaningless on ARM */ ret = notify_die(DIE_OOPS, str, regs, err, tsk->thread.trap_no, SIGSEGV); if (ret == NOTIFY_STOP) - return ret; + return 1; print_modules(); __show_regs(regs); printk(KERN_EMERG "Process %.*s (pid: %d, stack limit = 0x%p)\n", - TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk), thread + 1); + TASK_COMM_LEN, tsk->comm, task_pid_nr(tsk), end_of_stack(tsk)); if (!user_mode(regs) || in_interrupt()) { dump_mem(KERN_EMERG, "Stack: ", regs->ARM_sp, @@ -259,45 +259,77 @@ static int __die(const char *str, int err, struct thread_info *thread, struct pt dump_instr(KERN_EMERG, regs); } - return ret; + return 0; } -static DEFINE_RAW_SPINLOCK(die_lock); +static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED; +static int die_owner = -1; +static unsigned int die_nest_count; -/* - * This function is protected against re-entrancy. - */ -void die(const char *str, struct pt_regs *regs, int err) +static unsigned long oops_begin(void) { - struct thread_info *thread = current_thread_info(); - int ret; - enum bug_trap_type bug_type = BUG_TRAP_TYPE_NONE; + int cpu; + unsigned long flags; oops_enter(); - raw_spin_lock_irq(&die_lock); + /* racy, but better than risking deadlock. */ + raw_local_irq_save(flags); + cpu = smp_processor_id(); + if (!arch_spin_trylock(&die_lock)) { + if (cpu == die_owner) + /* nested oops. should stop eventually */; + else + arch_spin_lock(&die_lock); + } + die_nest_count++; + die_owner = cpu; console_verbose(); bust_spinlocks(1); - if (!user_mode(regs)) - bug_type = report_bug(regs->ARM_pc, regs); - if (bug_type != BUG_TRAP_TYPE_NONE) - str = "Oops - BUG"; - ret = __die(str, err, thread, regs); + return flags; +} - if (regs && kexec_should_crash(thread->task)) +static void oops_end(unsigned long flags, struct pt_regs *regs, int signr) +{ + if (regs && kexec_should_crash(current)) crash_kexec(regs); bust_spinlocks(0); + die_owner = -1; add_taint(TAINT_DIE); - raw_spin_unlock_irq(&die_lock); + die_nest_count--; + if (!die_nest_count) + /* Nest count reaches zero, release the lock. */ + arch_spin_unlock(&die_lock); + raw_local_irq_restore(flags); oops_exit(); if (in_interrupt()) panic("Fatal exception in interrupt"); if (panic_on_oops) panic("Fatal exception"); - if (ret != NOTIFY_STOP) - do_exit(SIGSEGV); + if (signr) + do_exit(signr); +} + +/* + * This function is protected against re-entrancy. + */ +void die(const char *str, struct pt_regs *regs, int err) +{ + enum bug_trap_type bug_type = BUG_TRAP_TYPE_NONE; + unsigned long flags = oops_begin(); + int sig = SIGSEGV; + + if (!user_mode(regs)) + bug_type = report_bug(regs->ARM_pc, regs); + if (bug_type != BUG_TRAP_TYPE_NONE) + str = "Oops - BUG"; + + if (__die(str, err, regs)) + sig = 0; + + oops_end(flags, regs, sig); } void arm_notify_die(const char *str, struct pt_regs *regs, -- 2.20.1