diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index bb9497724808..26dbdc37d219 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -110,13 +110,15 @@ static struct kgdb_bkpt kgdb_break[KGDB_MAX_BREAKPOINTS] = { */ atomic_t kgdb_active = ATOMIC_INIT(-1); EXPORT_SYMBOL_GPL(kgdb_active); +static DEFINE_RAW_SPINLOCK(dbg_master_lock); +static DEFINE_RAW_SPINLOCK(dbg_slave_lock); /* * We use NR_CPUs not PERCPU, in case kgdb is used to debug early * bootup code (which might not have percpu set up yet): */ -static atomic_t passive_cpu_wait[NR_CPUS]; -static atomic_t cpu_in_kgdb[NR_CPUS]; +static atomic_t masters_in_kgdb; +static atomic_t slaves_in_kgdb; static atomic_t kgdb_break_tasklet_var; atomic_t kgdb_setting_breakpoint; @@ -478,14 +480,23 @@ static void dbg_touch_watchdogs(void) rcu_cpu_stall_reset(); } -static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) +static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, + int exception_state) { unsigned long flags; int sstep_tries = 100; int error; - int i, cpu; + int cpu; int trace_on = 0; + int online_cpus = num_online_cpus(); + kgdb_info[ks->cpu].enter_kgdb++; + kgdb_info[ks->cpu].exception_state |= exception_state; + + if (exception_state == DCPU_WANT_MASTER) + atomic_inc(&masters_in_kgdb); + else + atomic_inc(&slaves_in_kgdb); kgdb_disable_hw_debug(ks->linux_regs); acquirelock: @@ -500,14 +511,15 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) kgdb_info[cpu].task = current; kgdb_info[cpu].ret_state = 0; kgdb_info[cpu].irq_depth = hardirq_count() >> HARDIRQ_SHIFT; - /* - * Make sure the above info reaches the primary CPU before - * our cpu_in_kgdb[] flag setting does: - */ - atomic_inc(&cpu_in_kgdb[cpu]); - if (exception_level == 1) + /* Make sure the above info reaches the primary CPU */ + smp_mb(); + + if (exception_level == 1) { + if (raw_spin_trylock(&dbg_master_lock)) + atomic_xchg(&kgdb_active, cpu); goto cpu_master_loop; + } /* * CPU will loop if it is a slave or request to become a kgdb @@ -519,10 +531,12 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) kgdb_info[cpu].exception_state &= ~DCPU_NEXT_MASTER; goto cpu_master_loop; } else if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) { - if (atomic_cmpxchg(&kgdb_active, -1, cpu) == cpu) + if (raw_spin_trylock(&dbg_master_lock)) { + atomic_xchg(&kgdb_active, cpu); break; + } } else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) { - if (!atomic_read(&passive_cpu_wait[cpu])) + if (!raw_spin_is_locked(&dbg_slave_lock)) goto return_normal; } else { return_normal: @@ -533,7 +547,11 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) arch_kgdb_ops.correct_hw_break(); if (trace_on) tracing_on(); - atomic_dec(&cpu_in_kgdb[cpu]); + kgdb_info[cpu].exception_state &= + ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); + kgdb_info[cpu].enter_kgdb--; + smp_mb__before_atomic_dec(); + atomic_dec(&slaves_in_kgdb); dbg_touch_watchdogs(); local_irq_restore(flags); return 0; @@ -551,6 +569,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) (kgdb_info[cpu].task && kgdb_info[cpu].task->pid != kgdb_sstep_pid) && --sstep_tries) { atomic_set(&kgdb_active, -1); + raw_spin_unlock(&dbg_master_lock); dbg_touch_watchdogs(); local_irq_restore(flags); @@ -576,10 +595,8 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) * Get the passive CPU lock which will hold all the non-primary * CPU in a spin state while the debugger is active */ - if (!kgdb_single_step) { - for (i = 0; i < NR_CPUS; i++) - atomic_inc(&passive_cpu_wait[i]); - } + if (!kgdb_single_step) + raw_spin_lock(&dbg_slave_lock); #ifdef CONFIG_SMP /* Signal the other CPUs to enter kgdb_wait() */ @@ -590,10 +607,9 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) /* * Wait for the other CPUs to be notified and be waiting for us: */ - for_each_online_cpu(i) { - while (kgdb_do_roundup && !atomic_read(&cpu_in_kgdb[i])) - cpu_relax(); - } + while (kgdb_do_roundup && (atomic_read(&masters_in_kgdb) + + atomic_read(&slaves_in_kgdb)) != online_cpus) + cpu_relax(); /* * At this point the primary processor is completely @@ -634,24 +650,11 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) if (dbg_io_ops->post_exception) dbg_io_ops->post_exception(); - atomic_dec(&cpu_in_kgdb[ks->cpu]); - if (!kgdb_single_step) { - for (i = NR_CPUS-1; i >= 0; i--) - atomic_dec(&passive_cpu_wait[i]); - /* - * Wait till all the CPUs have quit from the debugger, - * but allow a CPU that hit an exception and is - * waiting to become the master to remain in the debug - * core. - */ - for_each_online_cpu(i) { - while (kgdb_do_roundup && - atomic_read(&cpu_in_kgdb[i]) && - !(kgdb_info[i].exception_state & - DCPU_WANT_MASTER)) - cpu_relax(); - } + raw_spin_unlock(&dbg_slave_lock); + /* Wait till all the CPUs have quit from the debugger. */ + while (kgdb_do_roundup && atomic_read(&slaves_in_kgdb)) + cpu_relax(); } kgdb_restore: @@ -666,8 +669,15 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs) arch_kgdb_ops.correct_hw_break(); if (trace_on) tracing_on(); + + kgdb_info[cpu].exception_state &= + ~(DCPU_WANT_MASTER | DCPU_IS_SLAVE); + kgdb_info[cpu].enter_kgdb--; + smp_mb__before_atomic_dec(); + atomic_dec(&masters_in_kgdb); /* Free kgdb_active */ atomic_set(&kgdb_active, -1); + raw_spin_unlock(&dbg_master_lock); dbg_touch_watchdogs(); local_irq_restore(flags); @@ -686,7 +696,6 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) { struct kgdb_state kgdb_var; struct kgdb_state *ks = &kgdb_var; - int ret; ks->cpu = raw_smp_processor_id(); ks->ex_vector = evector; @@ -697,11 +706,10 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) if (kgdb_reenter_check(ks)) return 0; /* Ouch, double exception ! */ - kgdb_info[ks->cpu].exception_state |= DCPU_WANT_MASTER; - ret = kgdb_cpu_enter(ks, regs); - kgdb_info[ks->cpu].exception_state &= ~(DCPU_WANT_MASTER | - DCPU_IS_SLAVE); - return ret; + if (kgdb_info[ks->cpu].enter_kgdb != 0) + return 0; + + return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); } int kgdb_nmicallback(int cpu, void *regs) @@ -714,12 +722,9 @@ int kgdb_nmicallback(int cpu, void *regs) ks->cpu = cpu; ks->linux_regs = regs; - if (!atomic_read(&cpu_in_kgdb[cpu]) && - atomic_read(&kgdb_active) != -1 && - atomic_read(&kgdb_active) != cpu) { - kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE; - kgdb_cpu_enter(ks, regs); - kgdb_info[cpu].exception_state &= ~DCPU_IS_SLAVE; + if (kgdb_info[ks->cpu].enter_kgdb == 0 && + raw_spin_is_locked(&dbg_master_lock)) { + kgdb_cpu_enter(ks, regs, DCPU_IS_SLAVE); return 0; } #endif diff --git a/kernel/debug/debug_core.h b/kernel/debug/debug_core.h index c5d753d80f67..3494c28a7e7a 100644 --- a/kernel/debug/debug_core.h +++ b/kernel/debug/debug_core.h @@ -40,6 +40,7 @@ struct debuggerinfo_struct { int exception_state; int ret_state; int irq_depth; + int enter_kgdb; }; extern struct debuggerinfo_struct kgdb_info[];