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Code Issues Releases Activity

When running with INVARIANTS, the kernel contains extra checks. However,

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these assumptions may not hold true once we've panic'd. Therefore, the
checks hold less value after a panic.  Additionally, if one of the checks
fails while we are already panic'd, this creates a double-panic which can
interfere with debugging the original panic.

Therefore, this commit allows an administrator to suppress a response to
KASSERT checks after a panic by setting a tunable/sysctl.  The
tunable/sysctl (debug.kassert.suppress_in_panic) defaults to being
enabled.

Reviewed by:	kib
Sponsored by:	Netflix, Inc.
Differential Revision:	https://reviews.freebsd.org/D12920
This commit is contained in:
Jonathan T. Looney 2018-04-21 17:05:00 +00:00
parent 611c02b1d2
commit 44b71282b5
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=332860
1 changed files with 9 additions and 0 deletions
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9
sys/kern/kern_shutdown.c
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@ -642,6 +642,7 @@ static int kassert_do_log = 1;
static int kassert_log_pps_limit = 4;
static int kassert_log_mute_at = 0;
static int kassert_log_panic_at = 0;
static int kassert_suppress_in_panic = 1;
static int kassert_warnings = 0;
SYSCTL_NODE(_debug, OID_AUTO, kassert, CTLFLAG_RW, NULL, "kassert options");
@ -676,6 +677,10 @@ SYSCTL_INT(_debug_kassert, OID_AUTO, log_pps_limit, CTLFLAG_RWTUN,
SYSCTL_INT(_debug_kassert, OID_AUTO, log_mute_at, CTLFLAG_RWTUN,
&kassert_log_mute_at, 0, "max number of KASSERTS to log");
SYSCTL_INT(_debug_kassert, OID_AUTO, suppress_in_panic, CTLFLAG_RWTUN,
&kassert_suppress_in_panic, 0,
"KASSERTs will be suppressed while handling a panic");
static int kassert_sysctl_kassert(SYSCTL_HANDLER_ARGS);
SYSCTL_PROC(_debug_kassert, OID_AUTO, kassert,
@ -708,6 +713,10 @@ kassert_panic(const char *fmt, ...)
static char buf[256];
va_list ap;
/* If we already panic'd, don't create a double-fault. */
if (panicstr != NULL && kassert_suppress_in_panic)
return;
va_start(ap, fmt);
(void)vsnprintf(buf, sizeof(buf), fmt, ap);
va_end(ap);