Date: Sat, 3 Jan 2015 17:21:20 +0000 (UTC) From: Hans Petter Selasky <hselasky@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r276626 - head/sys/kern Message-ID: <201501031721.t03HLKHp060964@svn.freebsd.org>
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Author: hselasky Date: Sat Jan 3 17:21:19 2015 New Revision: 276626 URL: https://svnweb.freebsd.org/changeset/base/276626 Log: 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 Modified: head/sys/kern/kern_cons.c Modified: head/sys/kern/kern_cons.c ============================================================================== --- head/sys/kern/kern_cons.c Sat Jan 3 16:48:08 2015 (r276625) +++ head/sys/kern/kern_cons.c Sat Jan 3 17:21:19 2015 (r276626) @@ -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; }
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