From 04a8159ddf963628ac1167da87ca08b9a0297a7a Mon Sep 17 00:00:00 2001 From: Hans Petter Selasky Date: Sat, 3 Jan 2015 17:21:19 +0000 Subject: [PATCH] Rework r276532 a bit. Always avoid recursing into the console drivers clients, hence they might not handle it very well. This change allows debugging mutex problems with kernel console drivers when "debug.witness.skipspin=0" is set in the boot environment. MFC after: 1 week --- sys/kern/kern_cons.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/sys/kern/kern_cons.c b/sys/kern/kern_cons.c index 75f9c18ee9d..f91fe035f7a 100644 --- a/sys/kern/kern_cons.c +++ b/sys/kern/kern_cons.c @@ -512,6 +512,13 @@ cnputs(char *p) int unlock_reqd = 0; if (use_cnputs_mtx) { + /* + * NOTE: Debug prints and/or witness printouts in + * console driver clients can cause the "cnputs_mtx" + * mutex to recurse. Simply return if that happens. + */ + if (mtx_owned(&cnputs_mtx)) + return; mtx_lock_spin(&cnputs_mtx); unlock_reqd = 1; } @@ -601,13 +608,7 @@ static void cn_drvinit(void *unused) { - /* - * NOTE: Debug prints and/or witness printouts in console - * driver clients can cause the "cnputs_mtx" mutex to - * recurse. Make sure the "MTX_RECURSE" flags is set! - */ - mtx_init(&cnputs_mtx, "cnputs_mtx", NULL, MTX_SPIN | - MTX_NOWITNESS | MTX_RECURSE); + mtx_init(&cnputs_mtx, "cnputs_mtx", NULL, MTX_SPIN | MTX_NOWITNESS); use_cnputs_mtx = 1; }