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/usr/share/systemtap/runtime/linux

Name	Size	Mode	Actions
uprobes/	-	0755	rm
uprobes2/	-	0755	rm
access_process_vm.h	4311	0644	edit dl rm
addr-map.c	9749	0644	edit dl rm
alloc.c	15900	0644	edit dl rm
arith.c	16799	0644	edit dl rm
autoconf-514-panic.c	68	0644	edit dl rm
autoconf-access_ok_2args.c	90	0644	edit dl rm
autoconf-alloc-percpu-align.c	118	0644	edit dl rm
autoconf-asm-syscall.c	51	0644	edit dl rm
autoconf-atomic_fetch_add_unless.c	94	0644	edit dl rm
autoconf-bio-bi_opf.c	824	0644	edit dl rm
autoconf-blk-types.c	359	0644	edit dl rm
autoconf-compat-utimbuf.c	53	0644	edit dl rm
autoconf-compat_sigaction.c	448	0644	edit dl rm
autoconf-constant-tsc.c	63	0644	edit dl rm
autoconf-cpu-clock.c	1277	0644	edit dl rm
autoconf-dpath-path.c	121	0644	edit dl rm
autoconf-files_lookup_fd_raw.c	136	0644	edit dl rm
autoconf-from_kuid_munged.c	191	0644	edit dl rm
autoconf-fs_supers-hlist.c	354	0644	edit dl rm
autoconf-generated-compile.c	56	0644	edit dl rm
autoconf-genhd.c	201	0644	edit dl rm
autoconf-get-kretprobe.c	107	0644	edit dl rm
autoconf-get_user_pages-flags.c	1549	0644	edit dl rm
autoconf-get_user_pages-notask_struct.c	1301	0644	edit dl rm
autoconf-get_user_pages_remote-flags.c	1550	0644	edit dl rm
autoconf-get_user_pages_remote-flags_locked.c	1331	0644	edit dl rm
autoconf-get_user_pages_remote-notask_struct.c	1438	0644	edit dl rm
autoconf-grsecurity.c	219	0644	edit dl rm
autoconf-hlist-4args.c	296	0644	edit dl rm
autoconf-hlist_add_tail_rcu.c	112	0644	edit dl rm
autoconf-hrtimer-getset-expires.c	126	0644	edit dl rm
autoconf-hrtimer-rel.c	87	0644	edit dl rm
autoconf-hw_breakpoint_context.c	315	0644	edit dl rm
autoconf-inode-private.c	173	0644	edit dl rm
autoconf-inode-rwsem.c	172	0644	edit dl rm
autoconf-inode-uretprobes.c	264	0644	edit dl rm
autoconf-kernel_read-new-args.c	1030	0644	edit dl rm
autoconf-kprobe-symbol-name.c	90	0644	edit dl rm
autoconf-ktime-get-real.c	98	0644	edit dl rm
autoconf-linux-sched_headers.c	1678	0644	edit dl rm
autoconf-local-clock.c	1282	0644	edit dl rm
autoconf-lockdown-debugfs.c	102	0644	edit dl rm
autoconf-lockdown-kernel.c	90	0644	edit dl rm
autoconf-mm-context-vdso-base.c	117	0644	edit dl rm
autoconf-mm-context-vdso.c	114	0644	edit dl rm
autoconf-mm-shmempages.c	72	0644	edit dl rm
autoconf-mmap_lock.c	175	0644	edit dl rm
autoconf-module-sect-attrs.c	158	0644	edit dl rm
autoconf-module_layout.c	52	0644	edit dl rm
autoconf-mod_kallsyms.c	51	0644	edit dl rm
autoconf-nameidata.c	96	0644	edit dl rm
autoconf-netfilter-4_1.c	769	0644	edit dl rm
autoconf-netfilter-4_4.c	1460	0644	edit dl rm
autoconf-netfilter-313b.c	602	0644	edit dl rm
autoconf-netfilter.c	422	0644	edit dl rm
autoconf-old-inode-uprobes.c	357	0644	edit dl rm
autoconf-oneachcpu-retry.c	957	0644	edit dl rm
autoconf-pagefault_disable.c	137	0644	edit dl rm
autoconf-pde_data.c	226	0644	edit dl rm
autoconf-perf-structpid.c	444	0644	edit dl rm
autoconf-procfs-owner.c	158	0644	edit dl rm
autoconf-proc_ops.c	566	0644	edit dl rm
autoconf-rcu_is_watching.c	385	0644	edit dl rm
autoconf-real-parent.c	427	0644	edit dl rm
autoconf-regset.c	239	0644	edit dl rm
autoconf-relay-umode_t.c	730	0644	edit dl rm
autoconf-relay_buf-per_cpu_ptr.c	920	0644	edit dl rm
autoconf-ring_buffer-flags.c	112	0644	edit dl rm
autoconf-ring_buffer_lost_events.c	296	0644	edit dl rm
autoconf-ring_buffer_read_prepare.c	181	0644	edit dl rm
autoconf-save-stack-trace-no-bp.c	498	0644	edit dl rm
autoconf-save-stack-trace.c	501	0644	edit dl rm
autoconf-set_fs.c	221	0644	edit dl rm
autoconf-smpcall-4args.c	166	0644	edit dl rm
autoconf-smpcall-5args.c	169	0644	edit dl rm
autoconf-stack-trace-save-regs.c	176	0644	edit dl rm
autoconf-stacktrace_ops-int-address.c	409	0644	edit dl rm
autoconf-stacktrace_ops-warning.c	188	0644	edit dl rm
autoconf-syscall_get_args_3args.c	239	0644	edit dl rm
autoconf-task-state.c	550	0644	edit dl rm
autoconf-task-uid.c	152	0644	edit dl rm
autoconf-task_work-struct.c	219	0644	edit dl rm
autoconf-time32-old.c	52	0644	edit dl rm
autoconf-time32.c	53	0644	edit dl rm
autoconf-timerfd.c	232	0644	edit dl rm
autoconf-trace-printk.c	151	0644	edit dl rm
autoconf-tracepoint-has-data.c	493	0644	edit dl rm
autoconf-tracepoint-strings.c	233	0644	edit dl rm
autoconf-uaccess.c	28	0644	edit dl rm
autoconf-uapi-mount.c	52	0644	edit dl rm
autoconf-udelay_simple.c	90	0644	edit dl rm
autoconf-uidgid.c	50	0644	edit dl rm
autoconf-unwind-stack-trace.c	326	0644	edit dl rm
autoconf-uprobe-get-pc.c	374	0644	edit dl rm
autoconf-utrace-regset.c	273	0644	edit dl rm
autoconf-utrace-via-tracepoints.c	1712	0644	edit dl rm
autoconf-vm-area-pte.c	141	0644	edit dl rm
autoconf-walk-stack.c	217	0644	edit dl rm
autoconf-x86-fs.c	90	0644	edit dl rm
autoconf-x86-gs.c	90	0644	edit dl rm
autoconf-x86-uniregs.c	140	0644	edit dl rm
autoconf-x86-xfs.c	91	0644	edit dl rm
common_session_state.h	3249	0644	edit dl rm
compat_net.h	858	0644	edit dl rm
compat_structs.h	4409	0644	edit dl rm
compat_unistd.h	68384	0644	edit dl rm
copy.c	2717	0644	edit dl rm
debug.h	2978	0644	edit dl rm
io.c	5291	0644	edit dl rm
itrace.c	14874	0644	edit dl rm
kprobes.c	25126	0644	edit dl rm
loc2c-runtime.h	29874	0644	edit dl rm
map_list.h	1220	0644	edit dl rm
map_runtime.h	5266	0644	edit dl rm
namespaces.h	7128	0644	edit dl rm
netfilter.c	1410	0644	edit dl rm
perf.c	7596	0644	edit dl rm
perf.h	1272	0644	edit dl rm
perf_event_counter_context.c	336	0644	edit dl rm
perf_probe_handler_nmi.c	278	0644	edit dl rm
perf_read.h	959	0644	edit dl rm
print.c	11402	0644	edit dl rm
probe_lock.h	1807	0644	edit dl rm
regs-ia64.c	3741	0644	edit dl rm
regs.c	13490	0644	edit dl rm
runtime.h	12591	0644	edit dl rm
runtime_context.h	6089	0644	edit dl rm
runtime_defines.h	1041	0644	edit dl rm
stap_mmap_lock.h	343	0644	edit dl rm
stat_runtime.h	1774	0644	edit dl rm
stp_tls.h	1181	0644	edit dl rm
stp_tracepoint.c	11481	0644	edit dl rm
stp_tracepoint.h	2270	0644	edit dl rm
syscalls-common.h	976	0644	edit dl rm
task_finder.c	53860	0644	edit dl rm
task_finder2.c	57640	0644	edit dl rm
task_finder_map.c	5194	0644	edit dl rm
task_finder_stubs.c	2442	0644	edit dl rm
task_work_compatibility.h	1283	0644	edit dl rm
timer.c	2200	0644	edit dl rm
timer.h	1383	0644	edit dl rm
timer_compatibility.h	2317	0644	edit dl rm
uprobes-common.c	15573	0644	edit dl rm
uprobes-common.h	1653	0644	edit dl rm
uprobes-inc.h	484	0644	edit dl rm
uprobes-inode.c	34086	0644	edit dl rm

Edit: /usr/share/systemtap/runtime/linux/runtime_context.h (6089B)

/* -*- linux-c -*- 
 * Context Runtime Functions
 * Copyright (C) 2014 Red Hat Inc.
 *
 * This file is part of systemtap, and is free software.  You can
 * redistribute it and/or modify it under the terms of the GNU General
 * Public License (GPL); either version 2, or (at your option) any
 * later version.
 */

#ifndef _LINUX_RUNTIME_CONTEXT_H_
#define _LINUX_RUNTIME_CONTEXT_H_

/* Can't use a lock primitive for this because lock_acquire() has tracepoints */
static atomic_t _stp_contexts_busy_ctr = ATOMIC_INIT(0);

/* Per-cpu data is always initialized with zero filled. */
static DEFINE_PER_CPU(struct context *, contexts);

static int _stp_runtime_contexts_alloc(void)
{
	unsigned int cpu;

/* We don't use for_aech_possible_cpu() here since the number of possible
	 * CPUs may be very large even though there are many fewere online CPUs.
	 * For example, VMWare guests usually have 128 possible CPUs while only
	 * have a few online CPUs. Once the context structs were
	 * allocated for online CPUs at this point, we will discard any context
	 * fetching operations on any future online CPUs dynamically added
	 * through the kernel's CPU hotplug feature. Memory allocations of the
	 * context structs can only happen right here.
	 */
	for_each_online_cpu(cpu) {
		/* Module init, so in user context, safe to use
		 * "sleeping" allocation. */
		struct context *c = _stp_vzalloc_node(sizeof (struct context),
						      cpu_to_node(cpu));
		if (unlikely(c == NULL)) {
			_stp_error ("context (size %lu per cpu) allocation failed",
				    (unsigned long) sizeof (struct context));
			return -ENOMEM;
		}
		per_cpu(contexts, cpu) = c;
	}
	return 0;
}

static bool _stp_runtime_context_trylock(void)
{
	bool locked;

/* Need to disable preemption because of the smp_processor_id() call
	   in _stp_runtime_get_context(). */
	preempt_disable();

/* fast path to ignore new online CPUs without percpu context memory
	 * allocations. this also serves as an extra safe guard for NULL context
	 * pointers. */
	if (unlikely(_stp_runtime_get_context() == NULL)) {
		preempt_enable_no_resched();
		return false;
	}

locked = atomic_add_unless(&_stp_contexts_busy_ctr, 1, INT_MAX);
	if (!locked)
		preempt_enable_no_resched();

return locked;
}

static void _stp_runtime_context_unlock(void)
{
	atomic_dec(&_stp_contexts_busy_ctr);
	preempt_enable_no_resched();
}

/* We should be free of all probes by this time, but for example the timer for
 * _stp_ctl_work_callback may still be running and looking for contexts.  We
 * use _stp_contexts_busy_ctr to be sure its safe to free them.  */
static void _stp_runtime_contexts_free(void)
{
	unsigned int cpu;

/* Sync to make sure existing readers are done */
	while (atomic_cmpxchg(&_stp_contexts_busy_ctr, 0, INT_MAX))
		cpu_relax();

/* Now we can actually free the contexts */

/* NB We cannot use the for_each_online_cpu() here since online
	 * CPUs may get changed on-the-fly through the CPU hotplug feature
	 * of the kernel. We only allocated the context structs on original
	 * online CPUs when _stp_runtime_contexts_alloc() was called. And we
	 * cannot allocate new memory from within this context. */
	for_each_possible_cpu(cpu) {
		struct context *c = per_cpu(contexts, cpu);
		if (likely(c))
			_stp_vfree(c);
	}
}

static inline struct context * _stp_runtime_get_context(void)
{
	return per_cpu(contexts, smp_processor_id());
}

static struct context * _stp_runtime_entryfn_get_context(void)
{
	struct context* __restrict__ c = NULL;

if (!_stp_runtime_context_trylock())
		return NULL;

c = _stp_runtime_get_context();
	if (c != NULL) {
		if (!atomic_cmpxchg(&c->busy, 0, 1)) {
			// NB: Notice we're not releasing _stp_contexts_busy_ctr
			// here. We exepect the calling code to call
			// _stp_runtime_entryfn_get_context() and
			// _stp_runtime_entryfn_put_context() as a
			// pair.
			return c;
		}
	}
	_stp_runtime_context_unlock();
	return NULL;
}

static inline void _stp_runtime_entryfn_put_context(struct context *c)
{
	if (c) {
		atomic_set(&c->busy, 0);
		_stp_runtime_context_unlock();
	}
}

static void _stp_runtime_context_wait(void)
{
	int holdon;
	unsigned long hold_start;
	int hold_index;

hold_start = jiffies;
	hold_index = -1;
	do {
		int i;

holdon = 0;
		if (!_stp_runtime_context_trylock())
			break;

for_each_possible_cpu(i) {
			struct context *c = per_cpu(contexts, i);
			if (c != NULL
			    && atomic_read (& c->busy)) {
				holdon = 1;

/* Just in case things are really
				 * stuck, let's print some diagnostics. */
				if (time_after(jiffies, hold_start + HZ)  // > 1 second
				    && (i > hold_index)) { // not already printed
					hold_index = i;
					printk(KERN_ERR "%s context[%d] stuck: %s\n", THIS_MODULE->name, i, c->probe_point);
				}
			}
		}
		_stp_runtime_context_unlock();

/*
		 * Just in case things are really really stuck, a
		 * handler probably suffered a fault, and the kernel
		 * probably killed a task/thread already.  We can't be
		 * quite sure in what state everything is in, however
		 * auxiliary stuff like kprobes / uprobes / locks have
		 * already been unregistered.  So it's *probably* safe
		 * to pretend/assume/hope everything is OK, and let
		 * the cleanup finish.
		 *
		 * In the worst case, there may occur a fault, as a
		 * genuinely running probe handler tries to access
		 * script globals (about to be freed), or something
		 * accesses module memory (about to be unloaded).
		 * This is sometimes stinky, so the alternative
		 * (default) is to change from a livelock to a
		 * livelock that sleeps awhile.
		 */
#ifdef STAP_OVERRIDE_STUCK_CONTEXT
		if (time_after(jiffies, hold_start + HZ*10)) {  // > 10 seconds
			printk(KERN_ERR "%s overriding stuck context to allow module shutdown.", THIS_MODULE->name);
			holdon = 0; // allow loop to exit
		}
#else
		/* at least stop sucking down the staprun cpu */
		msleep(250);
#endif

/* NB: we run at least one of these during the
		 * shutdown sequence: */
		yield();	    /* aka schedule() and then some */
	} while (holdon);
}

#endif /* _LINUX_RUNTIME_CONTEXT_H_ */

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