Merge branch 'csd.2020.09.04a' into HEAD (6fe208f6) · Commits · 戴 / test

Documentation/admin-guide/kernel-parameters.txt

+4 −0

Original line number	Diff line number	Diff line
		@@ -3073,6 +3073,10 @@
		and gids from such clients. This is intended to ease
		migration from NFSv2/v3.

		nmi_backtrace.backtrace_idle [KNL]
		Dump stacks even of idle CPUs in response to an
		NMI stack-backtrace request.

		nmi_debug= [KNL,SH] Specify one or more actions to take
		when a NMI is triggered.
		Format: [state][,regs][,debounce][,die]

include/linux/smp.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -26,6 +26,9 @@ struct __call_single_data {
		struct {
		struct llist_node llist;
		unsigned int flags;
		#ifdef CONFIG_64BIT
		u16 src, dst;
		#endif
		};
		};
		smp_call_func_t func;

include/linux/smp_types.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -61,6 +61,9 @@ struct __call_single_node {
		unsigned int u_flags;
		atomic_t a_flags;
		};
		#ifdef CONFIG_64BIT
		u16 src, dst;
		#endif
		};

		#endif /* __LINUX_SMP_TYPES_H */

kernel/smp.c

+134 −0

Original line number	Diff line number	Diff line
		@@ -20,6 +20,9 @@
		#include <linux/sched.h>
		#include <linux/sched/idle.h>
		#include <linux/hypervisor.h>
		#include <linux/sched/clock.h>
		#include <linux/nmi.h>
		#include <linux/sched/debug.h>

		#include "smpboot.h"
		#include "sched/smp.h"
		@@ -96,6 +99,103 @@ void __init call_function_init(void)
		smpcfd_prepare_cpu(smp_processor_id());
		}

		#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG

		static DEFINE_PER_CPU(call_single_data_t *, cur_csd);
		static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
		static DEFINE_PER_CPU(void *, cur_csd_info);

		#define CSD_LOCK_TIMEOUT (5ULL * NSEC_PER_SEC)
		static atomic_t csd_bug_count = ATOMIC_INIT(0);

		/* Record current CSD work for current CPU, NULL to erase. */
		static void csd_lock_record(call_single_data_t *csd)
		{
		if (!csd) {
		smp_mb(); /* NULL cur_csd after unlock. */
		__this_cpu_write(cur_csd, NULL);
		return;
		}
		__this_cpu_write(cur_csd_func, csd->func);
		__this_cpu_write(cur_csd_info, csd->info);
		smp_wmb(); /* func and info before csd. */
		__this_cpu_write(cur_csd, csd);
		smp_mb(); /* Update cur_csd before function call. */
		/* Or before unlock, as the case may be. */
		}

		static __always_inline int csd_lock_wait_getcpu(call_single_data_t *csd)
		{
		unsigned int csd_type;

		csd_type = CSD_TYPE(csd);
		if (csd_type == CSD_TYPE_ASYNC \|\| csd_type == CSD_TYPE_SYNC)
		return csd->dst; /* Other CSD_TYPE_ values might not have ->dst. */
		return -1;
		}

		/*
		* Complain if too much time spent waiting. Note that only
		* the CSD_TYPE_SYNC/ASYNC types provide the destination CPU,
		* so waiting on other types gets much less information.
		*/
		static __always_inline bool csd_lock_wait_toolong(call_single_data_t csd, u64 ts0, u64 ts1, int *bug_id)
		{
		int cpu = -1;
		int cpux;
		bool firsttime;
		u64 ts2, ts_delta;
		call_single_data_t *cpu_cur_csd;
		unsigned int flags = READ_ONCE(csd->flags);

		if (!(flags & CSD_FLAG_LOCK)) {
		if (!unlikely(*bug_id))
		return true;
		cpu = csd_lock_wait_getcpu(csd);
		pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n",
		*bug_id, raw_smp_processor_id(), cpu);
		return true;
		}

		ts2 = sched_clock();
		ts_delta = ts2 - *ts1;
		if (likely(ts_delta <= CSD_LOCK_TIMEOUT))
		return false;

		firsttime = !*bug_id;
		if (firsttime)
		*bug_id = atomic_inc_return(&csd_bug_count);
		cpu = csd_lock_wait_getcpu(csd);
		if (WARN_ONCE(cpu < 0 \|\| cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu))
		cpux = 0;
		else
		cpux = cpu;
		cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */
		pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %llu ns for CPU#%02d %pS(%ps).\n",
		firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts2 - ts0,
		cpu, csd->func, csd->info);
		if (cpu_cur_csd && csd != cpu_cur_csd) {
		pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n",
		*bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)),
		READ_ONCE(per_cpu(cur_csd_info, cpux)));
		} else {
		pr_alert("\tcsd: CSD lock (#%d) %s.\n",
		*bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request");
		}
		if (cpu >= 0) {
		if (!trigger_single_cpu_backtrace(cpu))
		dump_cpu_task(cpu);
		if (!cpu_cur_csd) {
		pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu);
		arch_send_call_function_single_ipi(cpu);
		}
		}
		dump_stack();
		*ts1 = ts2;

		return false;
		}

		/*
		* csd_lock/csd_unlock used to serialize access to per-cpu csd resources
		*
		@@ -103,10 +203,30 @@ void __init call_function_init(void)
		* previous function call. For multi-cpu calls its even more interesting
		* as we'll have to ensure no other cpu is observing our csd.
		*/
		static __always_inline void csd_lock_wait(call_single_data_t *csd)
		{
		int bug_id = 0;
		u64 ts0, ts1;

		ts1 = ts0 = sched_clock();
		for (;;) {
		if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id))
		break;
		cpu_relax();
		}
		smp_acquire__after_ctrl_dep();
		}

		#else
		static void csd_lock_record(call_single_data_t *csd)
		{
		}

		static __always_inline void csd_lock_wait(call_single_data_t *csd)
		{
		smp_cond_load_acquire(&csd->flags, !(VAL & CSD_FLAG_LOCK));
		}
		#endif

		static __always_inline void csd_lock(call_single_data_t *csd)
		{
		@@ -166,9 +286,11 @@ static int generic_exec_single(int cpu, call_single_data_t *csd)
		* We can unlock early even for the synchronous on-stack case,
		* since we're doing this from the same CPU..
		*/
		csd_lock_record(csd);
		csd_unlock(csd);
		local_irq_save(flags);
		func(info);
		csd_lock_record(NULL);
		local_irq_restore(flags);
		return 0;
		}
		@@ -268,8 +390,10 @@ static void flush_smp_call_function_queue(bool warn_cpu_offline)
		entry = &csd_next->llist;
		}

		csd_lock_record(csd);
		func(info);
		csd_unlock(csd);
		csd_lock_record(NULL);
		} else {
		prev = &csd->llist;
		}
		@@ -296,8 +420,10 @@ static void flush_smp_call_function_queue(bool warn_cpu_offline)
		smp_call_func_t func = csd->func;
		void *info = csd->info;

		csd_lock_record(csd);
		csd_unlock(csd);
		func(info);
		csd_lock_record(NULL);
		} else if (type == CSD_TYPE_IRQ_WORK) {
		irq_work_single(csd);
		}
		@@ -375,6 +501,10 @@ int smp_call_function_single(int cpu, smp_call_func_t func, void *info,

		csd->func = func;
		csd->info = info;
		#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
		csd->src = smp_processor_id();
		csd->dst = cpu;
		#endif

		err = generic_exec_single(cpu, csd);

		@@ -540,6 +670,10 @@ static void smp_call_function_many_cond(const struct cpumask *mask,
		csd->flags \|= CSD_TYPE_SYNC;
		csd->func = func;
		csd->info = info;
		#ifdef CONFIG_CSD_LOCK_WAIT_DEBUG
		csd->src = smp_processor_id();
		csd->dst = cpu;
		#endif
		if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu)))
		__cpumask_set_cpu(cpu, cfd->cpumask_ipi);
		}

lib/Kconfig.debug

+11 −0

Original line number	Diff line number	Diff line
		@@ -1377,6 +1377,17 @@ config SCF_TORTURE_TEST
		module may be built after the fact on the running kernel to
		be tested, if desired.

		config CSD_LOCK_WAIT_DEBUG
		bool "Debugging for csd_lock_wait(), called from smp_call_function*()"
		depends on DEBUG_KERNEL
		depends on 64BIT
		default n
		help
		This option enables debug prints when CPUs are slow to respond
		to the smp_call_function*() IPI wrappers. These debug prints
		include the IPI handler function currently executing (if any)
		and relevant stack traces.

		endmenu # lock debugging

		config TRACE_IRQFLAGS

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