From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id A08B06B002B for ; Mon, 16 May 2011 17:54:31 -0400 (EDT) Received: by bwz17 with SMTP id 17so6404346bwz.14 for ; Mon, 16 May 2011 14:54:28 -0700 (PDT) Message-ID: <4DD19D10.3000201@gmail.com> Date: Mon, 16 May 2011 23:54:24 +0200 From: Jiri Slaby MIME-Version: 1.0 Subject: Re: [PATCH 2/3] printk: Add %ptc to safely print a task's comm References: <1305580757-13175-1-git-send-email-john.stultz@linaro.org> <1305580757-13175-3-git-send-email-john.stultz@linaro.org> In-Reply-To: <1305580757-13175-3-git-send-email-john.stultz@linaro.org> Content-Type: text/plain; charset=ISO-8859-2 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: John Stultz Cc: LKML , Ted Ts'o , KOSAKI Motohiro , David Rientjes , Dave Hansen , Andrew Morton , linux-mm@kvack.org On 05/16/2011 11:19 PM, John Stultz wrote: > Accessing task->comm requires proper locking. However in the past > access to current->comm could be done without locking. This > is no longer the case, so all comm access needs to be done > while holding the comm_lock. > > In my attempt to clean up unprotected comm access, I've noticed > most comm access is done for printk output. To simplify correct > locking in these cases, I've introduced a new %ptc format, > which will print the corresponding task's comm. > > Example use: > printk("%ptc: unaligned epc - sending SIGBUS.\n", current); > > CC: Ted Ts'o > CC: KOSAKI Motohiro > CC: David Rientjes > CC: Dave Hansen > CC: Andrew Morton > CC: linux-mm@kvack.org > Signed-off-by: John Stultz > --- > lib/vsprintf.c | 24 ++++++++++++++++++++++++ > 1 files changed, 24 insertions(+), 0 deletions(-) > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index bc0ac6b..b7a9953 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -797,6 +797,23 @@ char *uuid_string(char *buf, char *end, const u8 *addr, > return string(buf, end, uuid, spec); > } > > +static noinline_for_stack Actually, why noinline? Did your previous version have there some TASK_COMM_LEN buffer or anything on stack which is not there anymore? > +char *task_comm_string(char *buf, char *end, void *addr, > + struct printf_spec spec, const char *fmt) > +{ > + struct task_struct *tsk = addr; > + char *ret; > + unsigned long flags; > + > + spin_lock_irqsave(&tsk->comm_lock, flags); > + ret = string(buf, end, tsk->comm, spec); > + spin_unlock_irqrestore(&tsk->comm_lock, flags); > + > + return ret; > +} > + > + > + > int kptr_restrict = 1; > > /* thanks, -- js -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org