From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.12] helo=sc8-sf-mx2.sourceforge.net) by sc8-sf-list1.sourceforge.net with esmtp (Exim 4.30) id 1DXz5k-0000Rz-Ec for user-mode-linux-devel@lists.sourceforge.net; Tue, 17 May 2005 03:14:24 -0700 Received: from dgate1.fujitsu-siemens.com ([217.115.66.35]) by sc8-sf-mx2.sourceforge.net with esmtp (Exim 4.41) id 1DXz5j-0006pI-KP for user-mode-linux-devel@lists.sourceforge.net; Tue, 17 May 2005 03:14:24 -0700 Message-ID: <4289C3F9.9020105@fujitsu-siemens.com> From: Bodo Stroesser MIME-Version: 1.0 Subject: Re: [uml-devel] [patch 1/1] uml: replace pause with sigsuspend References: <20050516180143.95BDB1993E0@zion.home.lan> In-Reply-To: <20050516180143.95BDB1993E0@zion.home.lan> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: user-mode-linux-devel-admin@lists.sourceforge.net Errors-To: user-mode-linux-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: The user-mode Linux development list List-Post: List-Help: List-Subscribe: , List-Archive: Date: Tue, 17 May 2005 12:14:17 +0200 To: blaisorblade@yahoo.it Cc: jdike@addtoit.com, user-mode-linux-devel@lists.sourceforge.net I didn't have the time to test the patch, but I guess, it won't work. Maybe, the man pages for sigsuspend are somewhat missleading, saying: The sigsuspend call temporarily replaces the signal mask for the process with that given by mask and then suspends the process until a signal is received. Reading the code of sys_sigsuspend() in arch/i386/kernel/signal.c, you'll find that it will return to user only, if do_signal() returns 1. This will happen, if there was a signal to deliver. Ignored signals will not be delivered, so sys_sigsupend will not return on SIGWINCH, if SIGWINCH handler is set to SIG_IGN. So, for UML's winch_handler, there is no difference between pause() and sigsuspend(), because sigsuspend's feature of accepting a sigmask for use while waiting, in fact isn't needed here as the same mask is set already before with sigprocmask(). Bodo blaisorblade@yahoo.it wrote: > Replace pause with sigsuspend, to avoid needing to set an empty handler for SIGWINCH. > > Signed-off-by: Paolo 'Blaisorblade' Giarrusso > --- > > linux-2.6.git-paolo/arch/um/drivers/chan_user.c | 15 ++++----------- > 1 files changed, 4 insertions(+), 11 deletions(-) > > diff -puN arch/um/drivers/chan_user.c~uml-replace-pause-with-sigsuspend arch/um/drivers/chan_user.c > --- linux-2.6.git/arch/um/drivers/chan_user.c~uml-replace-pause-with-sigsuspend 2005-05-16 08:07:30.000000000 +0200 > +++ linux-2.6.git-paolo/arch/um/drivers/chan_user.c 2005-05-16 08:08:10.000000000 +0200 > @@ -67,10 +67,6 @@ error: > * it (see below for how we make sure to exit only on SIGWINCH). > */ > > -static void winch_handler(int sig) > -{ > -} > - > struct winch_data { > int pty_fd; > int pipe_fd; > @@ -93,14 +89,11 @@ static int winch_thread(void *arg) > printk("winch_thread : failed to write synchronization " > "byte, err = %d\n", -count); > > - /* We are not using SIG_IGN on purpose, so don't fix it as I thought to > - * do! If using SIG_IGN, the pause() call below would not stop on > - * SIGWINCH. */ > - > - signal(SIGWINCH, winch_handler); > sigfillset(&sigs); > sigdelset(&sigs, SIGWINCH); > - /* Block anything else than SIGWINCH. */ > + /* Block anything else than SIGWINCH. XXX: Actually, this may be removed > + * maybe, due to sigsuspend below, which replaces the signal mask, but > + * let's keep it.*/ > if(sigprocmask(SIG_SETMASK, &sigs, NULL) < 0){ > printk("winch_thread : sigprocmask failed, errno = %d\n", > errno); > @@ -130,7 +123,7 @@ static int winch_thread(void *arg) > while(1){ > /* This will be interrupted by SIGWINCH only, since other signals > * are blocked.*/ > - pause(); > + sigsuspend(&sigs); > > count = os_write_file(pipe_fd, &c, sizeof(c)); > if(count != sizeof(c)) > _ > > > ------------------------------------------------------- > This SF.Net email is sponsored by Oracle Space Sweepstakes > Want to be the first software developer in space? > Enter now for the Oracle Space Sweepstakes! > http://ads.osdn.com/?ad_id=7412&alloc_id=16344&op=click > _______________________________________________ > User-mode-linux-devel mailing list > User-mode-linux-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel ------------------------------------------------------- This SF.Net email is sponsored by Oracle Space Sweepstakes Want to be the first software developer in space? Enter now for the Oracle Space Sweepstakes! http://ads.osdn.com/?ad_id=7412&alloc_id=16344&op=click _______________________________________________ User-mode-linux-devel mailing list User-mode-linux-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel