Author: cem
Date: Wed Mar 16 04:22:32 2016
New Revision: 296927
URL: https://svnweb.freebsd.org/changeset/base/296927
Log:
fail(9): Upstreaming some fail point enhancements
This is several year's worth of fail point upgrades done at EMC Isilon. They
are interdependent enough that it makes sense to put a single diff up for
them.
Primarily, we added:
- Changing all mainline execution paths to be lockless, which lets us use fail
points in more sleep-sensitive areas, and allows more parallel execution
- A number of additional commands, including 'pause' that lets us do some
interesting deterministic repros of race conditions
- The ability to dump the stacks of all threads sleeping on a fail point
- A number of other API changes to allow marking up the fail point's context
in
the code, and firing callbacks before and after execution
- A man page update
Submitted by: Matthew Bryan <matthew.br...@isilon.com>
Reviewed by: cem (earlier version), jhb, kib, pho
With feedback from: bdrewery
Sponsored by: EMC / Isilon Storage Division
Differential Revision: https://reviews.freebsd.org/D5427
Modified:
head/share/man/man9/fail.9
head/sys/kern/kern_fail.c
head/sys/kern/subr_sleepqueue.c
head/sys/sys/fail.h
head/sys/sys/sleepqueue.h
Modified: head/share/man/man9/fail.9
==============================================================================
--- head/share/man/man9/fail.9 Wed Mar 16 04:05:02 2016 (r296926)
+++ head/share/man/man9/fail.9 Wed Mar 16 04:22:32 2016 (r296927)
@@ -26,25 +26,31 @@
.\"
.\" $FreeBSD$
.\"
-.Dd May 10, 2009
+.Dd February 02, 2016
.Dt FAIL 9
.Os
.Sh NAME
.Nm KFAIL_POINT_CODE ,
+.Nm KFAIL_POINT_CODE_FLAGS ,
+.Nm KFAIL_POINT_CODE_COND ,
.Nm KFAIL_POINT_RETURN ,
.Nm KFAIL_POINT_RETURN_VOID ,
.Nm KFAIL_POINT_ERROR ,
.Nm KFAIL_POINT_GOTO ,
+.Nm KFAIL_POINT_SLEEP_CALLBACKS ,
.Nm fail_point ,
.Nm DEBUG_FP
.Nd fail points
.Sh SYNOPSIS
.In sys/fail.h
.Fn KFAIL_POINT_CODE "parent" "name" "code"
+.Fn KFAIL_POINT_CODE_FLAGS "parent" "name" "flags" "code"
+.Fn KFAIL_POINT_CODE_COND "parent" "name" "cond" "flags" "code"
.Fn KFAIL_POINT_RETURN "parent" "name"
.Fn KFAIL_POINT_RETURN_VOID "parent" "name"
.Fn KFAIL_POINT_ERROR "parent" "name" "error_var"
.Fn KFAIL_POINT_GOTO "parent" "name" "error_var" "label"
+.Fn KFAIL_POINT_SLEEP_CALLBACKS "parent" "name" "pre_func" "pre_arg"
"post_func" "post_arg" "code"
.Sh DESCRIPTION
Fail points are used to add code points where errors may be injected
in a user controlled fashion.
@@ -77,6 +83,42 @@ argument, the evaluation of
is derived from the
.Fn return
value set in the sysctl MIB.
+.Pp
+Additionally,
+.Fn KFAIL_POINT_CODE_FLAGS
+provides a
+.Fa flags
+argument which controls the fail point's behaviour.
+This can be used to e.g., mark the fail point's context as non-sleepable,
+which causes the
+.Sy sleep
+action to be coerced to a busy wait.
+The supported flags are:
+.Bl -ohang -offset indent
+.It FAIL_POINT_USE_TIMEOUT_PATH
+Rather than sleeping on a
+.Fn sleep
+call, just fire the post-sleep function after a timeout fires.
+.It FAIL_POINT_NONSLEEPABLE
+Mark the fail point as being in a non-sleepable context, which coerces
+.Fn sleep
+calls to
+.Fn delay
+calls.
+.El
+.Pp
+Likewise,
+.Fn KFAIL_POINT_CODE_COND
+supplies a
+.Fa cond
+argument, which allows you to set the condition under which the fail point's
+code may fire.
+This is equivalent to:
+.Bd -literal
+ if (cond)
+ KFAIL_POINT_CODE_FLAGS(...);
+
+.Ed
See
.Sx SYSCTL VARIABLES
below.
@@ -107,26 +149,12 @@ Many base kernel MIBs can be found in th
tree (referenced in code by
.Sy DEBUG_FP ) .
.Pp
-The sysctl variable may be set using the following grammar:
+The sysctl variable may be set in a number of ways:
.Bd -literal
- <fail_point> ::
- <term> ( "->" <term> )*
-
- <term> ::
- ( (<float> "%") | (<integer> "*" ) )*
- <type>
- [ "(" <integer> ")" ]
- [ "[pid " <integer> "]" ]
-
- <float> ::
- <integer> [ "." <integer> ] |
- "." <integer>
-
- <type> ::
- "off" | "return" | "sleep" | "panic" | "break" | "print"
+ [<pct>%][<cnt>*]<type>[(args...)][-><more terms>]
.Ed
.Pp
-The <type> argument specifies which action to take:
+The <type> argument specifies which action to take; it can be one of:
.Bl -tag -width ".Dv return"
.It Sy off
Take no action (does not trigger fail point code)
@@ -140,13 +168,23 @@ Panic
Break into the debugger, or trap if there is no debugger support
.It Sy print
Print that the fail point executed
+.It Sy pause
+Threads sleep at the fail point until the fail point is set to
+.Sy off
+.It Sy yield
+Thread yields the cpu when the fail point is evaluated
+.It Sy delay
+Similar to sleep, but busy waits the cpu.
+(Useful in non-sleepable contexts.)
.El
.Pp
-The <float>% and <integer>* modifiers prior to <type> control when
+The <pct>% and <cnt>* modifiers prior to <type> control when
<type> is executed.
-The <float>% form (e.g. "1.2%") can be used to specify a
+The <pct>% form (e.g. "1.2%") can be used to specify a
probability that <type> will execute.
-The <integer>* form (e.g. "5*") can be used to specify the number of
+This is a decimal in the range (0, 100] which can specify up to
+1/10,000% precision.
+The <cnt>* form (e.g. "5*") can be used to specify the number of
times <type> should be executed before this <term> is disabled.
Only the last probability and the last count are used if multiple
are specified, i.e. "1.2%2%" is the same as "2%".
@@ -191,6 +229,10 @@ Return 5 once, when pid 1234 executes th
.Sh AUTHORS
.An -nosplit
This manual page was written by
+.Pp
+.An Matthew Bryan Aq Mt matthew.br...@isilon.com
+and
+.Pp
.An Zach Loafman Aq Mt z...@freebsd.org .
.Sh CAVEATS
It is easy to shoot yourself in the foot by setting fail points too
@@ -206,3 +248,10 @@ Currently,
.Fn fail_point_eval
does not verify whether the context is appropriate for calling
.Fn msleep .
+You can force it to evaluate a
+.Sy sleep
+action as a
+.Sy delay
+action by specifying the
+.Sy FAIL_POINT_NONSLEEPABLE
+flag at the point the fail point is declared.
Modified: head/sys/kern/kern_fail.c
==============================================================================
--- head/sys/kern/kern_fail.c Wed Mar 16 04:05:02 2016 (r296926)
+++ head/sys/kern/kern_fail.c Wed Mar 16 04:22:32 2016 (r296927)
@@ -57,12 +57,18 @@ __FBSDID("$FreeBSD$");
#include <sys/fail.h>
#include <sys/kernel.h>
#include <sys/libkern.h>
+#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/proc.h>
#include <sys/sbuf.h>
+#include <sys/sleepqueue.h>
+#include <sys/sx.h>
+#include <sys/sysctl.h>
+#include <sys/types.h>
+#include <machine/atomic.h>
#include <machine/stdarg.h>
#ifdef ILOG_DEFINE_FOR_FILE
@@ -72,11 +78,45 @@ ILOG_DEFINE_FOR_FILE(L_ISI_FAIL_POINT, L
static MALLOC_DEFINE(M_FAIL_POINT, "Fail Points", "fail points system");
#define fp_free(ptr) free(ptr, M_FAIL_POINT)
#define fp_malloc(size, flags) malloc((size), M_FAIL_POINT, (flags))
+#define fs_free(ptr) fp_free(ptr)
+#define fs_malloc() fp_malloc(sizeof(struct fail_point_setting), \
+ M_WAITOK | M_ZERO)
+
+ /**
+ * These define the wchans that are used for sleeping, pausing respectively.
+ * They are chosen arbitrarily but need to be distinct to the failpoint and
+ * the sleep/pause distinction.
+ */
+#define FP_SLEEP_CHANNEL(fp) (void*)(fp)
+#define FP_PAUSE_CHANNEL(fp) __DEVOLATILE(void*, &fp->fp_setting)
-static struct mtx g_fp_mtx;
-MTX_SYSINIT(g_fp_mtx, &g_fp_mtx, "fail point mtx", MTX_DEF);
-#define FP_LOCK() mtx_lock(&g_fp_mtx)
-#define FP_UNLOCK() mtx_unlock(&g_fp_mtx)
+/**
+ * Don't allow more than this many entries in a fail point set by sysctl.
+ * The 99.99...% case is to have 1 entry. I can't imagine having this many
+ * entries, so it should not limit us. Saves on re-mallocs while holding
+ * a non-sleepable lock.
+ */
+#define FP_MAX_ENTRY_COUNT 20
+
+/* Used to drain sbufs to the sysctl output */
+int fail_sysctl_drain_func(void *, const char *, int);
+
+/* Head of tailq of struct fail_point_entry */
+TAILQ_HEAD(fail_point_entry_queue, fail_point_entry);
+
+/**
+ * fp entries garbage list; outstanding entries are cleaned up in the
+ * garbage collector
+ */
+STAILQ_HEAD(fail_point_setting_garbage, fail_point_setting);
+static struct fail_point_setting_garbage fp_setting_garbage =
+ STAILQ_HEAD_INITIALIZER(fp_setting_garbage);
+static struct mtx mtx_garbage_list;
+MTX_SYSINIT(mtx_garbage_list, &mtx_garbage_list, "fail point garbage mtx",
+ MTX_SPIN);
+
+static struct sx sx_fp_set;
+SX_SYSINIT(sx_fp_set, &sx_fp_set, "fail point set sx");
/**
* Failpoint types.
@@ -90,7 +130,11 @@ enum fail_point_t {
FAIL_POINT_BREAK, /**< break into the debugger */
FAIL_POINT_PRINT, /**< print a message */
FAIL_POINT_SLEEP, /**< sleep for some msecs */
- FAIL_POINT_NUMTYPES
+ FAIL_POINT_PAUSE, /**< sleep until failpoint is set to off */
+ FAIL_POINT_YIELD, /**< yield the cpu */
+ FAIL_POINT_DELAY, /**< busy wait the cpu */
+ FAIL_POINT_NUMTYPES,
+ FAIL_POINT_INVALID = -1
};
static struct {
@@ -104,53 +148,307 @@ static struct {
[FAIL_POINT_BREAK] = FP_TYPE_NM_LEN("break"),
[FAIL_POINT_PRINT] = FP_TYPE_NM_LEN("print"),
[FAIL_POINT_SLEEP] = FP_TYPE_NM_LEN("sleep"),
+ [FAIL_POINT_PAUSE] = FP_TYPE_NM_LEN("pause"),
+ [FAIL_POINT_YIELD] = FP_TYPE_NM_LEN("yield"),
+ [FAIL_POINT_DELAY] = FP_TYPE_NM_LEN("delay"),
};
+#define FE_COUNT_UNTRACKED (INT_MIN)
+
/**
* Internal structure tracking a single term of a complete failpoint.
* @ingroup failpoint_private
*/
struct fail_point_entry {
- enum fail_point_t fe_type; /**< type of entry */
+ volatile bool fe_stale;
+ enum fail_point_t fe_type; /**< type of entry */
int fe_arg; /**< argument to type (e.g. return
value) */
int fe_prob; /**< likelihood of firing in millionths
*/
- int fe_count; /**< number of times to fire, 0 means
always */
+ int fe_count; /**< number of times to fire, -1 means
infinite */
pid_t fe_pid; /**< only fail for this process */
- TAILQ_ENTRY(fail_point_entry) fe_entries; /**< next entry in fail point
*/
+ struct fail_point *fe_parent; /**< backpointer to fp */
+ TAILQ_ENTRY(fail_point_entry) fe_entries; /**< next entry ptr */
+};
+
+struct fail_point_setting {
+ STAILQ_ENTRY(fail_point_setting) fs_garbage_link;
+ struct fail_point_entry_queue fp_entry_queue;
+ struct fail_point * fs_parent;
+ struct mtx feq_mtx; /* Gives fail_point_pause something to do. */
+};
+
+/**
+ * Defines stating the equivalent of probablilty one (100%)
+ */
+enum {
+ PROB_MAX = 1000000, /* probability between zero and this number */
+ PROB_DIGITS = 6 /* number of zero's in above number */
};
+/* Get a ref on an fp's fp_setting */
+static inline struct fail_point_setting *fail_point_setting_get_ref(
+ struct fail_point *fp);
+/* Release a ref on an fp_setting */
+static inline void fail_point_setting_release_ref(struct fail_point *fp);
+/* Allocate and initialize a struct fail_point_setting */
+static struct fail_point_setting *fail_point_setting_new(struct
+ fail_point *);
+/* Free a struct fail_point_setting */
+static void fail_point_setting_destroy(struct fail_point_setting *fp_setting);
+/* Allocate and initialize a struct fail_point_entry */
+static struct fail_point_entry *fail_point_entry_new(struct
+ fail_point_setting *);
+/* Free a struct fail_point_entry */
+static void fail_point_entry_destroy(struct fail_point_entry *fp_entry);
+/* Append fp setting to garbage list */
+static inline void fail_point_setting_garbage_append(
+ struct fail_point_setting *fp_setting);
+/* Swap fp's setting with fp_setting_new */
+static inline struct fail_point_setting *
+ fail_point_swap_settings(struct fail_point *fp,
+ struct fail_point_setting *fp_setting_new);
+/* Free up any zero-ref setting in the garbage queue */
+static void fail_point_garbage_collect(void);
+/* If this fail point's setting are empty, then swap it out to NULL. */
+static inline void fail_point_eval_swap_out(struct fail_point *fp,
+ struct fail_point_setting *fp_setting);
+
+bool
+fail_point_is_off(struct fail_point *fp)
+{
+ bool return_val;
+ struct fail_point_setting *fp_setting;
+ struct fail_point_entry *ent;
+
+ return_val = true;
+
+ fp_setting = fail_point_setting_get_ref(fp);
+ if (fp_setting != NULL) {
+ TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue,
+ fe_entries) {
+ if (!ent->fe_stale) {
+ return_val = false;
+ break;
+ }
+ }
+ }
+ fail_point_setting_release_ref(fp);
+
+ return (return_val);
+}
+
+/* Allocate and initialize a struct fail_point_setting */
+static struct fail_point_setting *
+fail_point_setting_new(struct fail_point *fp)
+{
+ struct fail_point_setting *fs_new;
+
+ fs_new = fs_malloc();
+ fs_new->fs_parent = fp;
+ TAILQ_INIT(&fs_new->fp_entry_queue);
+ mtx_init(&fs_new->feq_mtx, "fail point entries", NULL, MTX_SPIN);
+
+ fail_point_setting_garbage_append(fs_new);
+
+ return (fs_new);
+}
+
+/* Free a struct fail_point_setting */
+static void
+fail_point_setting_destroy(struct fail_point_setting *fp_setting)
+{
+ struct fail_point_entry *ent;
+
+ while (!TAILQ_EMPTY(&fp_setting->fp_entry_queue)) {
+ ent = TAILQ_FIRST(&fp_setting->fp_entry_queue);
+ TAILQ_REMOVE(&fp_setting->fp_entry_queue, ent, fe_entries);
+ fail_point_entry_destroy(ent);
+ }
+
+ fs_free(fp_setting);
+}
+
+/* Allocate and initialize a struct fail_point_entry */
+static struct fail_point_entry *
+fail_point_entry_new(struct fail_point_setting *fp_setting)
+{
+ struct fail_point_entry *fp_entry;
+
+ fp_entry = fp_malloc(sizeof(struct fail_point_entry),
+ M_WAITOK | M_ZERO);
+ fp_entry->fe_parent = fp_setting->fs_parent;
+ fp_entry->fe_prob = PROB_MAX;
+ fp_entry->fe_pid = NO_PID;
+ fp_entry->fe_count = FE_COUNT_UNTRACKED;
+ TAILQ_INSERT_TAIL(&fp_setting->fp_entry_queue, fp_entry,
+ fe_entries);
+
+ return (fp_entry);
+}
+
+/* Free a struct fail_point_entry */
+static void
+fail_point_entry_destroy(struct fail_point_entry *fp_entry)
+{
+
+ fp_free(fp_entry);
+}
+
+/* Get a ref on an fp's fp_setting */
+static inline struct fail_point_setting *
+fail_point_setting_get_ref(struct fail_point *fp)
+{
+ struct fail_point_setting *fp_setting;
+
+ /* Invariant: if we have a ref, our pointer to fp_setting is safe */
+ atomic_add_acq_32(&fp->fp_ref_cnt, 1);
+ fp_setting = fp->fp_setting;
+
+ return (fp_setting);
+}
+
+/* Release a ref on an fp_setting */
+static inline void
+fail_point_setting_release_ref(struct fail_point *fp)
+{
+
+ KASSERT(&fp->fp_ref_cnt > 0, ("Attempting to deref w/no refs"));
+ atomic_subtract_rel_32(&fp->fp_ref_cnt, 1);
+}
+
+/* Append fp entries to fp garbage list */
+static inline void
+fail_point_setting_garbage_append(struct fail_point_setting *fp_setting)
+{
+
+ mtx_lock_spin(&mtx_garbage_list);
+ STAILQ_INSERT_TAIL(&fp_setting_garbage, fp_setting,
+ fs_garbage_link);
+ mtx_unlock_spin(&mtx_garbage_list);
+}
+
+/* Swap fp's entries with fp_setting_new */
+static struct fail_point_setting *
+fail_point_swap_settings(struct fail_point *fp,
+ struct fail_point_setting *fp_setting_new)
+{
+ struct fail_point_setting *fp_setting_old;
+
+ fp_setting_old = fp->fp_setting;
+ fp->fp_setting = fp_setting_new;
+
+ return (fp_setting_old);
+}
+
+static inline void
+fail_point_eval_swap_out(struct fail_point *fp,
+ struct fail_point_setting *fp_setting)
+{
+
+ /* We may have already been swapped out and replaced; ignore. */
+ if (fp->fp_setting == fp_setting)
+ fail_point_swap_settings(fp, NULL);
+}
+
+/* Free up any zero-ref entries in the garbage queue */
+static void
+fail_point_garbage_collect()
+{
+ struct fail_point_setting *fs_current, *fs_next;
+ struct fail_point_setting_garbage fp_ents_free_list;
+
+ /**
+ * We will transfer the entries to free to fp_ents_free_list while
holding
+ * the spin mutex, then free it after we drop the lock. This avoids
+ * triggering witness due to sleepable mutexes in the memory
+ * allocator.
+ */
+ STAILQ_INIT(&fp_ents_free_list);
+
+ mtx_lock_spin(&mtx_garbage_list);
+ STAILQ_FOREACH_SAFE(fs_current, &fp_setting_garbage, fs_garbage_link,
+ fs_next) {
+ if (fs_current->fs_parent->fp_setting != fs_current &&
+ fs_current->fs_parent->fp_ref_cnt == 0) {
+ STAILQ_REMOVE(&fp_setting_garbage, fs_current,
+ fail_point_setting, fs_garbage_link);
+ STAILQ_INSERT_HEAD(&fp_ents_free_list, fs_current,
+ fs_garbage_link);
+ }
+ }
+ mtx_unlock_spin(&mtx_garbage_list);
+
+ STAILQ_FOREACH_SAFE(fs_current, &fp_ents_free_list, fs_garbage_link,
+ fs_next)
+ fail_point_setting_destroy(fs_current);
+}
+
+/* Drain out all refs from this fail point */
+static inline void
+fail_point_drain(struct fail_point *fp, int expected_ref)
+{
+ struct fail_point_setting *entries;
+
+ entries = fail_point_swap_settings(fp, NULL);
+ /**
+ * We have unpaused all threads; so we will wait no longer
+ * than the time taken for the longest remaining sleep, or
+ * the length of time of a long-running code block.
+ */
+ while (fp->fp_ref_cnt > expected_ref) {
+ wakeup(FP_PAUSE_CHANNEL(fp));
+ tsleep(&fp, PWAIT, "fail_point_drain", hz / 100);
+ }
+ fail_point_swap_settings(fp, entries);
+}
+
static inline void
-fail_point_sleep(struct fail_point *fp, struct fail_point_entry *ent,
- int msecs, enum fail_point_return_code *pret)
+fail_point_pause(struct fail_point *fp, enum fail_point_return_code *pret,
+ struct mtx *mtx_sleep)
{
- /* convert from millisecs to ticks, rounding up */
- int timo = ((msecs * hz) + 999) / 1000;
+
+ if (fp->fp_pre_sleep_fn)
+ fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
+
+ msleep_spin(FP_PAUSE_CHANNEL(fp), mtx_sleep, "failpt", 0);
+
+ if (fp->fp_post_sleep_fn)
+ fp->fp_post_sleep_fn(fp->fp_post_sleep_arg);
+}
+
+static inline void
+fail_point_sleep(struct fail_point *fp, int msecs,
+ enum fail_point_return_code *pret)
+{
+ int timo;
+
+ /* Convert from millisecs to ticks, rounding up */
+ timo = howmany(msecs * hz, 1000);
if (timo > 0) {
- if (fp->fp_sleep_fn == NULL) {
- msleep(fp, &g_fp_mtx, PWAIT, "failpt", timo);
+ if (!(fp->fp_flags & FAIL_POINT_USE_TIMEOUT_PATH)) {
+ if (fp->fp_pre_sleep_fn)
+ fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
+
+ tsleep(FP_SLEEP_CHANNEL(fp), PWAIT, "failpt", timo);
+
+ if (fp->fp_post_sleep_fn)
+ fp->fp_post_sleep_fn(fp->fp_post_sleep_arg);
} else {
- timeout(fp->fp_sleep_fn, fp->fp_sleep_arg, timo);
+ if (fp->fp_pre_sleep_fn)
+ fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
+
+ timeout(fp->fp_post_sleep_fn, fp->fp_post_sleep_arg,
+ timo);
*pret = FAIL_POINT_RC_QUEUED;
}
}
}
-
-/**
- * Defines stating the equivalent of probablilty one (100%)
- */
-enum {
- PROB_MAX = 1000000, /* probability between zero and this number */
- PROB_DIGITS = 6, /* number of zero's in above number */
-};
-
-static char *parse_fail_point(struct fail_point_entries *, char *);
-static char *parse_term(struct fail_point_entries *, char *);
+static char *parse_fail_point(struct fail_point_setting *, char *);
+static char *parse_term(struct fail_point_setting *, char *);
static char *parse_number(int *out_units, int *out_decimal, char *);
static char *parse_type(struct fail_point_entry *, char *);
-static void free_entry(struct fail_point_entries *, struct fail_point_entry *);
-static void clear_entries(struct fail_point_entries *);
/**
* Initialize a fail_point. The name is formed in a printf-like fashion
@@ -167,7 +465,7 @@ fail_point_init(struct fail_point *fp, c
char *name;
int n;
- TAILQ_INIT(&fp->fp_entries);
+ fp->fp_setting = NULL;
fp->fp_flags = 0;
/* Figure out the size of the name. */
@@ -185,25 +483,33 @@ fail_point_init(struct fail_point *fp, c
fp->fp_name = name;
fp->fp_location = "";
fp->fp_flags |= FAIL_POINT_DYNAMIC_NAME;
- fp->fp_sleep_fn = NULL;
- fp->fp_sleep_arg = NULL;
+ fp->fp_pre_sleep_fn = NULL;
+ fp->fp_pre_sleep_arg = NULL;
+ fp->fp_post_sleep_fn = NULL;
+ fp->fp_post_sleep_arg = NULL;
}
/**
- * Free the resources held by a fail_point.
- *
+ * Free the resources held by a fail_point, and wake any paused threads.
+ * Thou shalt not allow threads to hit this fail point after you enter this
+ * function, nor shall you call this multiple times for a given fp.
* @ingroup failpoint
*/
void
fail_point_destroy(struct fail_point *fp)
{
+ fail_point_drain(fp, 0);
+
if ((fp->fp_flags & FAIL_POINT_DYNAMIC_NAME) != 0) {
fp_free(__DECONST(void *, fp->fp_name));
fp->fp_name = NULL;
}
fp->fp_flags = 0;
- clear_entries(&fp->fp_entries);
+
+ sx_xlock(&sx_fp_set);
+ fail_point_garbage_collect();
+ sx_xunlock(&sx_fp_set);
}
/**
@@ -216,21 +522,51 @@ fail_point_destroy(struct fail_point *fp
enum fail_point_return_code
fail_point_eval_nontrivial(struct fail_point *fp, int *return_value)
{
- enum fail_point_return_code ret = FAIL_POINT_RC_CONTINUE;
- struct fail_point_entry *ent, *next;
+ bool execute = false;
+ struct fail_point_entry *ent;
+ struct fail_point_setting *fp_setting;
+ enum fail_point_return_code ret;
+ int cont;
+ int count;
int msecs;
+ int usecs;
+
+ ret = FAIL_POINT_RC_CONTINUE;
+ cont = 0; /* don't continue by default */
- FP_LOCK();
+ fp_setting = fail_point_setting_get_ref(fp);
+ if (fp_setting == NULL)
+ goto abort;
- TAILQ_FOREACH_SAFE(ent, &fp->fp_entries, fe_entries, next) {
- int cont = 0; /* don't continue by default */
+ TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue, fe_entries) {
+
+ if (ent->fe_stale)
+ continue;
if (ent->fe_prob < PROB_MAX &&
ent->fe_prob < random() % PROB_MAX)
continue;
+
if (ent->fe_pid != NO_PID && ent->fe_pid != curproc->p_pid)
continue;
+ if (ent->fe_count != FE_COUNT_UNTRACKED) {
+ count = ent->fe_count;
+ while (count > 0) {
+ if (atomic_cmpset_32(&ent->fe_count, count,
count - 1)) {
+ count--;
+ execute = true;
+ break;
+ }
+ count = ent->fe_count;
+ }
+ if (execute == false)
+ /* We lost the race; consider the entry stale
and bail now */
+ continue;
+ if (count == 0)
+ ent->fe_stale = true;
+ }
+
switch (ent->fe_type) {
case FAIL_POINT_PANIC:
panic("fail point %s panicking", fp->fp_name);
@@ -244,7 +580,7 @@ fail_point_eval_nontrivial(struct fail_p
case FAIL_POINT_BREAK:
printf("fail point %s breaking to debugger\n",
- fp->fp_name);
+ fp->fp_name);
breakpoint();
break;
@@ -254,51 +590,95 @@ fail_point_eval_nontrivial(struct fail_p
break;
case FAIL_POINT_SLEEP:
- /*
- * Free the entry now if necessary, since
- * we're about to drop the mutex and sleep.
- */
msecs = ent->fe_arg;
- if (ent->fe_count > 0 && --ent->fe_count == 0) {
- free_entry(&fp->fp_entries, ent);
- ent = NULL;
- }
-
if (msecs)
- fail_point_sleep(fp, ent, msecs, &ret);
+ fail_point_sleep(fp, msecs, &ret);
+ break;
+
+ case FAIL_POINT_PAUSE:
+ /**
+ * Pausing is inherently strange with multiple
+ * entries given our design. That is because some
+ * entries could be unreachable, for instance in cases
like:
+ * pause->return. We can never reach the return entry.
+ * The sysctl layer actually truncates all entries after
+ * a pause for this reason.
+ */
+ mtx_lock_spin(&fp_setting->feq_mtx);
+ fail_point_pause(fp, &ret, &fp_setting->feq_mtx);
+ mtx_unlock_spin(&fp_setting->feq_mtx);
+ break;
+
+ case FAIL_POINT_YIELD:
+ kern_yield(-1);
+ break;
+
+ case FAIL_POINT_DELAY:
+ usecs = ent->fe_arg;
+ DELAY(usecs);
break;
default:
break;
}
- if (ent != NULL && ent->fe_count > 0 && --ent->fe_count == 0)
- free_entry(&fp->fp_entries, ent);
if (cont == 0)
break;
}
- /* Get rid of "off"s at the end. */
- while ((ent = TAILQ_LAST(&fp->fp_entries, fail_point_entries)) &&
- ent->fe_type == FAIL_POINT_OFF)
- free_entry(&fp->fp_entries, ent);
+ if (fail_point_is_off(fp))
+ fail_point_eval_swap_out(fp, fp_setting);
- FP_UNLOCK();
+abort:
+ fail_point_setting_release_ref(fp);
return (ret);
+
}
/**
* Translate internal fail_point structure into human-readable text.
*/
static void
-fail_point_get(struct fail_point *fp, struct sbuf *sb)
+fail_point_get(struct fail_point *fp, struct sbuf *sb,
+ bool verbose)
{
struct fail_point_entry *ent;
+ struct fail_point_setting *fp_setting;
+ struct fail_point_entry *fp_entry_cpy;
+ int cnt_sleeping;
+ int idx;
+ int printed_entry_count;
+
+ cnt_sleeping = 0;
+ idx = 0;
+ printed_entry_count = 0;
+
+ fp_entry_cpy = fp_malloc(sizeof(struct fail_point_entry) *
+ (FP_MAX_ENTRY_COUNT + 1), M_WAITOK);
+
+ fp_setting = fail_point_setting_get_ref(fp);
+
+ if (fp_setting != NULL) {
+ TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue, fe_entries) {
+ if (ent->fe_stale)
+ continue;
- FP_LOCK();
+ KASSERT(printed_entry_count < FP_MAX_ENTRY_COUNT,
+ ("FP entry list larger than allowed"));
- TAILQ_FOREACH(ent, &fp->fp_entries, fe_entries) {
+ fp_entry_cpy[printed_entry_count] = *ent;
+ ++printed_entry_count;
+ }
+ }
+ fail_point_setting_release_ref(fp);
+
+ /* This is our equivalent of a NULL terminator */
+ fp_entry_cpy[printed_entry_count].fe_type = FAIL_POINT_INVALID;
+
+ while (idx < printed_entry_count) {
+ ent = &fp_entry_cpy[idx];
+ ++idx;
if (ent->fe_prob < PROB_MAX) {
int decimal = ent->fe_prob % (PROB_MAX / 100);
int units = ent->fe_prob / (PROB_MAX / 100);
@@ -313,7 +693,7 @@ fail_point_get(struct fail_point *fp, st
}
sbuf_printf(sb, "%%");
}
- if (ent->fe_count > 0)
+ if (ent->fe_count >= 0)
sbuf_printf(sb, "%d*", ent->fe_count);
sbuf_printf(sb, "%s", fail_type_strings[ent->fe_type].name);
if (ent->fe_arg)
@@ -323,10 +703,29 @@ fail_point_get(struct fail_point *fp, st
if (TAILQ_NEXT(ent, fe_entries))
sbuf_printf(sb, "->");
}
- if (TAILQ_EMPTY(&fp->fp_entries))
+ if (!printed_entry_count)
sbuf_printf(sb, "off");
- FP_UNLOCK();
+ fp_free(fp_entry_cpy);
+ if (verbose) {
+ /* Print number of sleeping threads. queue=0 is the argument
+ * used by msleep when sending our threads to sleep. */
+ sbuf_printf(sb, "\nsleeping_thread_stacks = {\n");
+ sleepq_sbuf_print_stacks(sb, FP_SLEEP_CHANNEL(fp), 0,
+ &cnt_sleeping);
+
+ sbuf_printf(sb, "},\n");
+ sbuf_printf(sb, "sleeping_thread_count = %d,\n",
+ cnt_sleeping);
+
+ sbuf_printf(sb, "paused_thread_stacks = {\n");
+ sleepq_sbuf_print_stacks(sb, FP_PAUSE_CHANNEL(fp), 0,
+ &cnt_sleeping);
+
+ sbuf_printf(sb, "},\n");
+ sbuf_printf(sb, "paused_thread_count = %d\n",
+ cnt_sleeping);
+ }
}
/**
@@ -336,38 +735,91 @@ fail_point_get(struct fail_point *fp, st
static int
fail_point_set(struct fail_point *fp, char *buf)
{
- int error = 0;
struct fail_point_entry *ent, *ent_next;
- struct fail_point_entries new_entries;
+ struct fail_point_setting *entries;
+ bool should_wake_paused;
+ bool should_truncate;
+ int error;
+
+ error = 0;
+ should_wake_paused = false;
+ should_truncate = false;
/* Parse new entries. */
- TAILQ_INIT(&new_entries);
- if (!parse_fail_point(&new_entries, buf)) {
- clear_entries(&new_entries);
+ /**
+ * ref protects our new malloc'd stuff from being garbage collected
+ * before we link it.
+ */
+ fail_point_setting_get_ref(fp);
+ entries = fail_point_setting_new(fp);
+ if (parse_fail_point(entries, buf) == NULL) {
+ STAILQ_REMOVE(&fp_setting_garbage, entries,
+ fail_point_setting, fs_garbage_link);
+ fail_point_setting_destroy(entries);
error = EINVAL;
goto end;
}
- FP_LOCK();
-
- /* Move new entries in. */
- TAILQ_SWAP(&fp->fp_entries, &new_entries, fail_point_entry, fe_entries);
- clear_entries(&new_entries);
+ /**
+ * Transfer the entries we are going to keep to a new list.
+ * Get rid of useless zero probability entries, and entries with hit
+ * count 0.
+ * If 'off' is present, and it has no hit count set, then all entries
+ * after it are discarded since they are unreachable.
+ */
+ TAILQ_FOREACH_SAFE(ent, &entries->fp_entry_queue, fe_entries, ent_next)
{
+ if (ent->fe_prob == 0 || ent->fe_count == 0) {
+ printf("Discarding entry which cannot execute %s\n",
+ fail_type_strings[ent->fe_type].name);
+ TAILQ_REMOVE(&entries->fp_entry_queue, ent,
+ fe_entries);
+ fp_free(ent);
+ continue;
+ } else if (should_truncate) {
+ printf("Discarding unreachable entry %s\n",
+ fail_type_strings[ent->fe_type].name);
+ TAILQ_REMOVE(&entries->fp_entry_queue, ent,
+ fe_entries);
+ fp_free(ent);
+ continue;
+ }
- /* Get rid of useless zero probability entries. */
- TAILQ_FOREACH_SAFE(ent, &fp->fp_entries, fe_entries, ent_next) {
- if (ent->fe_prob == 0)
- free_entry(&fp->fp_entries, ent);
+ if (ent->fe_type == FAIL_POINT_OFF) {
+ should_wake_paused = true;
+ if (ent->fe_count == FE_COUNT_UNTRACKED) {
+ should_truncate = true;
+ TAILQ_REMOVE(&entries->fp_entry_queue, ent,
+ fe_entries);
+ fp_free(ent);
+ }
+ } else if (ent->fe_type == FAIL_POINT_PAUSE) {
+ should_truncate = true;
+ } else if (ent->fe_type == FAIL_POINT_SLEEP && (fp->fp_flags &
+ FAIL_POINT_NONSLEEPABLE)) {
+ /**
+ * If this fail point is annotated as being in a
+ * non-sleepable ctx, convert sleep to delay and
+ * convert the msec argument to usecs.
+ */
+ printf("Sleep call request on fail point in "
+ "non-sleepable context; using delay instead "
+ "of sleep\n");
+ ent->fe_type = FAIL_POINT_DELAY;
+ ent->fe_arg *= 1000;
+ }
}
- /* Get rid of "off"s at the end. */
- while ((ent = TAILQ_LAST(&fp->fp_entries, fail_point_entries)) &&
- ent->fe_type == FAIL_POINT_OFF)
- free_entry(&fp->fp_entries, ent);
-
- FP_UNLOCK();
+ if (TAILQ_EMPTY(&entries->fp_entry_queue)) {
+ entries = fail_point_swap_settings(fp, NULL);
+ if (entries != NULL)
+ wakeup(FP_PAUSE_CHANNEL(fp));
+ } else {
+ if (should_wake_paused)
+ wakeup(FP_PAUSE_CHANNEL(fp));
+ fail_point_swap_settings(fp, entries);
+ }
- end:
+end:
#ifdef IWARNING
if (error)
IWARNING("Failed to set %s %s to %s",
@@ -377,6 +829,7 @@ fail_point_set(struct fail_point *fp, ch
fp->fp_name, fp->fp_location, buf);
#endif /* IWARNING */
+ fail_point_setting_release_ref(fp);
return (error);
}
@@ -385,25 +838,33 @@ fail_point_set(struct fail_point *fp, ch
/**
* Handle kernel failpoint set/get.
*/
+
int
fail_point_sysctl(SYSCTL_HANDLER_ARGS)
{
- struct fail_point *fp = arg1;
- char *buf = NULL;
+ struct fail_point *fp;
+ char *buf;
+ struct sbuf *sb_check;
struct sbuf sb;
int error;
- /* Retrieving */
- sbuf_new(&sb, NULL, 128, SBUF_AUTOEXTEND | SBUF_INCLUDENUL);
- fail_point_get(fp, &sb);
- sbuf_trim(&sb);
- error = sbuf_finish(&sb);
- if (error == 0)
- error = SYSCTL_OUT(req, sbuf_data(&sb), sbuf_len(&sb));
- sbuf_delete(&sb);
+ error = 0;
+ fp = arg1;
+ buf = NULL;
+
+ sb_check = sbuf_new(&sb, NULL, 1024, SBUF_AUTOEXTEND);
+ if (sb_check != &sb)
+ return (ENOMEM);
+
+ sbuf_set_drain(&sb, (sbuf_drain_func *)fail_sysctl_drain_func, req);
/* Setting */
- if (!error && req->newptr) {
*** DIFF OUTPUT TRUNCATED AT 1000 LINES ***
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