Date: Thu, 19 Nov 2020 18:03:41 +0000 (UTC) From: Mitchell Horne <mhorne@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r367848 - in head: share/man/man4 sys/kern Message-ID: <202011191803.0AJI3fS7039667@repo.freebsd.org>
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Author: mhorne Date: Thu Nov 19 18:03:40 2020 New Revision: 367848 URL: https://svnweb.freebsd.org/changeset/base/367848 Log: Add an option for entering KDB on recursive panics There are many cases where one would choose avoid entering the debugger on a normal panic, opting instead to reboot and possibly save a kernel dump. However, recursive kernel panics are an unusual case that might warrant attention from a human, so provide a secondary tunable, debug.debugger_on_recursive_panic, to allow entering the debugger only when this occurs. For for simplicity in maintaining existing behaviour, the tunable defaults to zero. Reviewed by: cem, markj Sponsored by: NetApp, Inc. Sponsored by: Klara, Inc. Differential Revision: https://reviews.freebsd.org/D27271 Modified: head/share/man/man4/ddb.4 head/sys/kern/kern_shutdown.c Modified: head/share/man/man4/ddb.4 ============================================================================== --- head/share/man/man4/ddb.4 Thu Nov 19 17:54:41 2020 (r367847) +++ head/share/man/man4/ddb.4 Thu Nov 19 18:03:40 2020 (r367848) @@ -26,7 +26,7 @@ .\" .\" $FreeBSD$ .\" -.Dd October 17, 2019 +.Dd November 19, 2020 .Dt DDB 4 .Os .Sh NAME @@ -87,6 +87,16 @@ which is the default unless the .Dv KDB_UNATTENDED option is specified. +Similarly, if the +.Va debug.debugger_on_recursive_panic +variable is set to +.Dv 1 , +then the debugger will be invoked on a recursive kernel panic. +This variable has a default value of +.Dv 0 , +and has no effect if +.Va debug.debugger_on_panic +is already set non-zero. .Pp The current location is called .Va dot . Modified: head/sys/kern/kern_shutdown.c ============================================================================== --- head/sys/kern/kern_shutdown.c Thu Nov 19 17:54:41 2020 (r367847) +++ head/sys/kern/kern_shutdown.c Thu Nov 19 18:03:40 2020 (r367848) @@ -127,6 +127,11 @@ SYSCTL_INT(_debug, OID_AUTO, debugger_on_panic, CTLFLAG_RWTUN | CTLFLAG_SECURE, &debugger_on_panic, 0, "Run debugger on kernel panic"); +static bool debugger_on_recursive_panic = false; +SYSCTL_BOOL(_debug, OID_AUTO, debugger_on_recursive_panic, + CTLFLAG_RWTUN | CTLFLAG_SECURE, + &debugger_on_recursive_panic, 0, "Run debugger on recursive kernel panic"); + int debugger_on_trap = 0; SYSCTL_INT(_debug, OID_AUTO, debugger_on_trap, CTLFLAG_RWTUN | CTLFLAG_SECURE, @@ -899,6 +904,8 @@ vpanic(const char *fmt, va_list ap) kdb_backtrace(); if (debugger_on_panic) kdb_enter(KDB_WHY_PANIC, "panic"); + else if (!newpanic && debugger_on_recursive_panic) + kdb_enter(KDB_WHY_PANIC, "re-panic"); #endif /*thread_lock(td); */ td->td_flags |= TDF_INPANIC;
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