From patchwork Thu May 12 23:02:50 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Stultz X-Patchwork-Id: 1468 Return-Path: Delivered-To: unknown Received: from imap.gmail.com (74.125.159.109) by localhost6.localdomain6 with IMAP4-SSL; 08 Jun 2011 14:52:13 -0000 Delivered-To: patches@linaro.org Received: by 10.224.61.3 with SMTP id r3cs126743qah; Thu, 12 May 2011 16:03:04 -0700 (PDT) Received: by 10.90.156.12 with SMTP id d12mr801498age.46.1305241383549; Thu, 12 May 2011 16:03:03 -0700 (PDT) Received: from e8.ny.us.ibm.com (e8.ny.us.ibm.com [32.97.182.138]) by mx.google.com with ESMTPS id i35si3654512anh.39.2011.05.12.16.03.02 (version=TLSv1/SSLv3 cipher=OTHER); Thu, 12 May 2011 16:03:02 -0700 (PDT) Received-SPF: pass (google.com: domain of jstultz@us.ibm.com designates 32.97.182.138 as permitted sender) client-ip=32.97.182.138; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jstultz@us.ibm.com designates 32.97.182.138 as permitted sender) smtp.mail=jstultz@us.ibm.com Received: from d01relay06.pok.ibm.com (d01relay06.pok.ibm.com [9.56.227.116]) by e8.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id p4CMaeUq007705; Thu, 12 May 2011 18:36:40 -0400 Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by d01relay06.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p4CN2ukt1441820; Thu, 12 May 2011 19:02:56 -0400 Received: from d01av01.pok.ibm.com (loopback [127.0.0.1]) by d01av01.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p4CN2tFb008717; Thu, 12 May 2011 19:02:55 -0400 Received: from kernel.beaverton.ibm.com (kernel.beaverton.ibm.com [9.47.67.96]) by d01av01.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id p4CN2tZp008703; Thu, 12 May 2011 19:02:55 -0400 Received: by kernel.beaverton.ibm.com (Postfix, from userid 1056) id 8FF0B1E7510; Thu, 12 May 2011 16:02:54 -0700 (PDT) From: John Stultz To: LKML Cc: John Stultz , "Ted Ts'o" , KOSAKI Motohiro , David Rientjes , Dave Hansen , Andrew Morton , linux-mm@kvack.org Subject: [PATCH 2/3] printk: Add %ptc to safely print a task's comm Date: Thu, 12 May 2011 16:02:50 -0700 Message-Id: <1305241371-25276-3-git-send-email-john.stultz@linaro.org> X-Mailer: git-send-email 1.7.3.2.146.gca209 In-Reply-To: <1305241371-25276-1-git-send-email-john.stultz@linaro.org> References: <1305241371-25276-1-git-send-email-john.stultz@linaro.org> 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 | 27 +++++++++++++++++++++++++++ 1 files changed, 27 insertions(+), 0 deletions(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index bc0ac6b..5abbe94 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -797,6 +797,26 @@ char *uuid_string(char *buf, char *end, const u8 *addr, return string(buf, end, uuid, spec); } +static noinline_for_stack +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 seq; + + do { + seq = read_seqbegin(&tsk->comm_lock); + + ret = string(buf, end, tsk->comm, spec); + + } while (read_seqretry(&tsk->comm_lock, seq)); + + return ret; +} + + + int kptr_restrict = 1; /* @@ -864,6 +884,12 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, } switch (*fmt) { + case 't': + switch (fmt[1]) { + case 'c': + return task_comm_string(buf, end, ptr, spec, fmt); + } + break; case 'F': case 'f': ptr = dereference_function_descriptor(ptr); @@ -1151,6 +1177,7 @@ qualifier: * http://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-00 * %pU[bBlL] print a UUID/GUID in big or little endian using lower or upper * case. + * %ptc outputs the task's comm name * %n is ignored * * The return value is the number of characters which would