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kgdb: eliminate kgdb_wait(), all cpus enter the same way
This is a kgdb architectural change to have all the cpus (master or slave) enter the same function. A cpu that hits an exception (wants to be the master cpu) will call kgdb_handle_exception() from the trap handler and then invoke a kgdb_roundup_cpu() to synchronize the other cpus and bring them into the kgdb_handle_exception() as well. A slave cpu will enter kgdb_handle_exception() from the kgdb_nmicallback() and set the exception state to note that the processor is a slave. Previously the salve cpu would have called kgdb_wait(). This change allows the debug core to change cpus without resuming the system in order to inspect arch specific cpu information. Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
This commit is contained in:
Jason Wessel
parent
cad08acebf
commit
62fae31219
165
kernel/kgdb.c
165
kernel/kgdb.c
@ -69,9 +69,16 @@ struct kgdb_state {
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struct pt_regs *linux_regs;
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};
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/* Exception state values */
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#define DCPU_WANT_MASTER 0x1 /* Waiting to become a master kgdb cpu */
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#define DCPU_NEXT_MASTER 0x2 /* Transition from one master cpu to another */
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#define DCPU_IS_SLAVE 0x4 /* Slave cpu enter exception */
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#define DCPU_SSTEP 0x8 /* CPU is single stepping */
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static struct debuggerinfo_struct {
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void *debuggerinfo;
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struct task_struct *task;
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int exception_state;
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} kgdb_info[NR_CPUS];
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/**
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@ -557,49 +564,6 @@ static struct task_struct *getthread(struct pt_regs *regs, int tid)
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return find_task_by_pid_ns(tid, &init_pid_ns);
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}
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/*
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* CPU debug state control:
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*/
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#ifdef CONFIG_SMP
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static void kgdb_wait(struct pt_regs *regs)
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{
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unsigned long flags;
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int cpu;
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local_irq_save(flags);
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cpu = raw_smp_processor_id();
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kgdb_info[cpu].debuggerinfo = regs;
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kgdb_info[cpu].task = current;
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/*
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* Make sure the above info reaches the primary CPU before
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* our cpu_in_kgdb[] flag setting does:
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*/
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smp_wmb();
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atomic_set(&cpu_in_kgdb[cpu], 1);
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/* Disable any cpu specific hw breakpoints */
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kgdb_disable_hw_debug(regs);
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/* Wait till primary CPU is done with debugging */
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while (atomic_read(&passive_cpu_wait[cpu]))
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cpu_relax();
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kgdb_info[cpu].debuggerinfo = NULL;
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kgdb_info[cpu].task = NULL;
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/* fix up hardware debug registers on local cpu */
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if (arch_kgdb_ops.correct_hw_break)
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arch_kgdb_ops.correct_hw_break();
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/* Signal the primary CPU that we are done: */
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atomic_set(&cpu_in_kgdb[cpu], 0);
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touch_softlockup_watchdog_sync();
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clocksource_touch_watchdog();
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local_irq_restore(flags);
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}
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#endif
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/*
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* Some architectures need cache flushes when we set/clear a
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* breakpoint:
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@ -1395,34 +1359,12 @@ static int kgdb_reenter_check(struct kgdb_state *ks)
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return 1;
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}
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/*
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* kgdb_handle_exception() - main entry point from a kernel exception
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*
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* Locking hierarchy:
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* interface locks, if any (begin_session)
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* kgdb lock (kgdb_active)
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*/
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int
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kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
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static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
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{
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struct kgdb_state kgdb_var;
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struct kgdb_state *ks = &kgdb_var;
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unsigned long flags;
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int sstep_tries = 100;
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int error = 0;
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int i, cpu;
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ks->cpu = raw_smp_processor_id();
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ks->ex_vector = evector;
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ks->signo = signo;
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ks->ex_vector = evector;
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ks->err_code = ecode;
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ks->kgdb_usethreadid = 0;
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ks->linux_regs = regs;
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if (kgdb_reenter_check(ks))
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return 0; /* Ouch, double exception ! */
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acquirelock:
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/*
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* Interrupts will be restored by the 'trap return' code, except when
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@ -1430,13 +1372,42 @@ acquirelock:
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*/
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local_irq_save(flags);
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cpu = raw_smp_processor_id();
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cpu = ks->cpu;
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kgdb_info[cpu].debuggerinfo = regs;
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kgdb_info[cpu].task = current;
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/*
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* Make sure the above info reaches the primary CPU before
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* our cpu_in_kgdb[] flag setting does:
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*/
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smp_wmb();
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atomic_set(&cpu_in_kgdb[cpu], 1);
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/*
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* Acquire the kgdb_active lock:
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* CPU will loop if it is a slave or request to become a kgdb
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* master cpu and acquire the kgdb_active lock:
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*/
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while (atomic_cmpxchg(&kgdb_active, -1, cpu) != -1)
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while (1) {
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if (kgdb_info[cpu].exception_state & DCPU_WANT_MASTER) {
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if (atomic_cmpxchg(&kgdb_active, -1, cpu) == cpu)
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break;
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} else if (kgdb_info[cpu].exception_state & DCPU_IS_SLAVE) {
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if (!atomic_read(&passive_cpu_wait[cpu]))
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goto return_normal;
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} else {
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return_normal:
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/* Return to normal operation by executing any
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* hw breakpoint fixup.
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*/
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if (arch_kgdb_ops.correct_hw_break)
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arch_kgdb_ops.correct_hw_break();
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atomic_set(&cpu_in_kgdb[cpu], 0);
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touch_softlockup_watchdog_sync();
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clocksource_touch_watchdog();
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local_irq_restore(flags);
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return 0;
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}
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cpu_relax();
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}
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/*
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* For single stepping, try to only enter on the processor
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@ -1470,9 +1441,6 @@ acquirelock:
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if (kgdb_io_ops->pre_exception)
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kgdb_io_ops->pre_exception();
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kgdb_info[ks->cpu].debuggerinfo = ks->linux_regs;
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kgdb_info[ks->cpu].task = current;
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kgdb_disable_hw_debug(ks->linux_regs);
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/*
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@ -1484,12 +1452,6 @@ acquirelock:
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atomic_set(&passive_cpu_wait[i], 1);
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}
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/*
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* spin_lock code is good enough as a barrier so we don't
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* need one here:
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*/
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atomic_set(&cpu_in_kgdb[ks->cpu], 1);
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#ifdef CONFIG_SMP
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/* Signal the other CPUs to enter kgdb_wait() */
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if ((!kgdb_single_step) && kgdb_do_roundup)
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@ -1521,8 +1483,6 @@ acquirelock:
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if (kgdb_io_ops->post_exception)
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kgdb_io_ops->post_exception();
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kgdb_info[ks->cpu].debuggerinfo = NULL;
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kgdb_info[ks->cpu].task = NULL;
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atomic_set(&cpu_in_kgdb[ks->cpu], 0);
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if (!kgdb_single_step) {
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@ -1555,13 +1515,52 @@ kgdb_restore:
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return error;
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}
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/*
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* kgdb_handle_exception() - main entry point from a kernel exception
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*
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* Locking hierarchy:
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* interface locks, if any (begin_session)
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* kgdb lock (kgdb_active)
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*/
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int
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kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs)
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{
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struct kgdb_state kgdb_var;
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struct kgdb_state *ks = &kgdb_var;
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int ret;
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ks->cpu = raw_smp_processor_id();
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ks->ex_vector = evector;
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ks->signo = signo;
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ks->ex_vector = evector;
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ks->err_code = ecode;
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ks->kgdb_usethreadid = 0;
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ks->linux_regs = regs;
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if (kgdb_reenter_check(ks))
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return 0; /* Ouch, double exception ! */
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kgdb_info[ks->cpu].exception_state |= DCPU_WANT_MASTER;
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ret = kgdb_cpu_enter(ks, regs);
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kgdb_info[ks->cpu].exception_state &= ~DCPU_WANT_MASTER;
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return ret;
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}
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int kgdb_nmicallback(int cpu, void *regs)
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{
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#ifdef CONFIG_SMP
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struct kgdb_state kgdb_var;
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struct kgdb_state *ks = &kgdb_var;
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memset(ks, 0, sizeof(struct kgdb_state));
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ks->cpu = cpu;
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ks->linux_regs = regs;
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if (!atomic_read(&cpu_in_kgdb[cpu]) &&
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atomic_read(&kgdb_active) != cpu &&
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atomic_read(&cpu_in_kgdb[atomic_read(&kgdb_active)])) {
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kgdb_wait((struct pt_regs *)regs);
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atomic_read(&kgdb_active) != -1 &&
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atomic_read(&kgdb_active) != cpu) {
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kgdb_info[cpu].exception_state |= DCPU_IS_SLAVE;
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kgdb_cpu_enter(ks, regs);
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kgdb_info[cpu].exception_state &= ~DCPU_IS_SLAVE;
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return 0;
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}
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#endif
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