From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELsUgTitxThYsmuvtRfci8if24Lc+a+YNHabYW7TYnlQ2TeydZtUkUyIn8KDqKFsNEsiM2s0 ARC-Seal: i=1; a=rsa-sha256; t=1521040394; cv=none; d=google.com; s=arc-20160816; b=W+qhe75ikpYJOthpYKxBODUI09770fnig6Ty5JXUqlb1AVkutN0Ajn97oh2HYgNt/a 0elxkWOewAqZ2xx7VkAN4lj0v61o366X/9U98Jd24ZH5kHCx+9BTDijNVlX7dc37ayYc 6D9Y6jjzO8p6wQzRGoR8zOrofsj6YATWFO4A81i0Gq3hx/7maVHY8/W1mIO5Iq/6gwpR B2rQNo37ybo8ArNXUHJRhDZ5SqjHbQDEuw/MnNyLEsCE4k+Zrwm/Lk8KAKBEiVgUW63/ NkRUvNrjRuIJpBTM9x8lDJTenG5buIkIgCbSv7J7jOEPuIoCS2qtrO+2O5+ffTZGt0Rf aT+w== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:content-language:content-transfer-encoding:in-reply-to :mime-version:user-agent:date:from:references:cc:to:subject :arc-authentication-results; bh=Gpl99H+g+4NLnAIRi1cPvUOcZIHoCgO9Icw0mI8vTMQ=; b=MwLuJloCVlzMaMDdTOyofFv9cvFIkcdAtM7kL70f8PYe9AGBrvYzEOaokrd0+ij4Ac ASK6x67wfQQ8p2K1hZHfVM0LNZQOWjwwFqSUiPyEziM+htoketOhqVy/W8mihkLeMVke ji9QbF8YPKVh0+vFhNVf4YtULMs8j8ZQh5EpzttItyBrvtsiLp2hPre+Vb9W+/ynvHw5 gzOYU862uV2kQZK941HUo4b2JEx7eBblA3aWBxZssssqZrMC5Ww20VMqaufcPuJcKdjJ RoReGN3yJgeurdMkDV1DFABtVYO1HjWvyQDTXkGlSdvXikmJOZvXr55JyVFmL/gWDIZr ojUg== ARC-Authentication-Results: i=1; mx.google.com; spf=neutral (google.com: 148.163.156.1 is neither permitted nor denied by best guess record for domain of ravi.bangoria@linux.vnet.ibm.com) smtp.mailfrom=ravi.bangoria@linux.vnet.ibm.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=ibm.com Authentication-Results: mx.google.com; spf=neutral (google.com: 148.163.156.1 is neither permitted nor denied by best guess record for domain of ravi.bangoria@linux.vnet.ibm.com) smtp.mailfrom=ravi.bangoria@linux.vnet.ibm.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=ibm.com Subject: Re: [PATCH 6/8] trace_uprobe/sdt: Fix multiple update of same reference counter To: Masami Hiramatsu Cc: oleg@redhat.com, peterz@infradead.org, srikar@linux.vnet.ibm.com, acme@kernel.org, ananth@linux.vnet.ibm.com, akpm@linux-foundation.org, alexander.shishkin@linux.intel.com, alexis.berlemont@gmail.com, corbet@lwn.net, dan.j.williams@intel.com, gregkh@linuxfoundation.org, huawei.libin@huawei.com, hughd@google.com, jack@suse.cz, jglisse@redhat.com, jolsa@redhat.com, kan.liang@intel.com, kirill.shutemov@linux.intel.com, kjlx@templeofstupid.com, kstewart@linuxfoundation.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mhocko@suse.com, milian.wolff@kdab.com, mingo@redhat.com, namhyung@kernel.org, naveen.n.rao@linux.vnet.ibm.com, pc@us.ibm.com, pombredanne@nexb.com, rostedt@goodmis.org, tglx@linutronix.de, tmricht@linux.vnet.ibm.com, willy@infradead.org, yao.jin@linux.intel.com, fengguang.wu@intel.com, Ravi Bangoria References: <20180313125603.19819-1-ravi.bangoria@linux.vnet.ibm.com> <20180313125603.19819-7-ravi.bangoria@linux.vnet.ibm.com> <20180314231540.b98c74a153255f59f54ebc46@kernel.org> From: Ravi Bangoria Date: Wed, 14 Mar 2018 20:45:14 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180314231540.b98c74a153255f59f54ebc46@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-TM-AS-GCONF: 00 x-cbid: 18031415-0040-0000-0000-000004206C0F X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18031415-0041-0000-0000-0000262370F8 Message-Id: <1e51042b-d05b-dd55-82e6-818bb5be03d1@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-03-14_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1803140171 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1594827186487084438?= X-GMAIL-MSGID: =?utf-8?q?1594926452567596902?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 03/14/2018 07:45 PM, Masami Hiramatsu wrote: > On Tue, 13 Mar 2018 18:26:01 +0530 > Ravi Bangoria wrote: > >> For tiny binaries/libraries, different mmap regions points to the >> same file portion. In such cases, we may increment reference counter >> multiple times. But while de-registration, reference counter will get >> decremented only by once leaving reference counter > 0 even if no one >> is tracing on that marker. >> >> Ensure increment and decrement happens in sync by keeping list of >> mms in trace_uprobe. Increment reference counter only if mm is not >> present in the list and decrement only if mm is present in the list. >> >> Example >> >> # echo "p:sdt_tick/loop2 /tmp/tick:0x6e4(0x10036)" > uprobe_events >> >> Before patch: >> >> # perf stat -a -e sdt_tick:loop2 >> # /tmp/tick >> # dd if=/proc/`pgrep tick`/mem bs=1 count=1 skip=$(( 0x10020036 )) 2>/dev/null | xxd >> 0000000: 02 . >> >> # pkill perf >> # dd if=/proc/`pgrep tick`/mem bs=1 count=1 skip=$(( 0x10020036 )) 2>/dev/null | xxd >> 0000000: 01 . >> >> After patch: >> >> # perf stat -a -e sdt_tick:loop2 >> # /tmp/tick >> # dd if=/proc/`pgrep tick`/mem bs=1 count=1 skip=$(( 0x10020036 )) 2>/dev/null | xxd >> 0000000: 01 . >> >> # pkill perf >> # dd if=/proc/`pgrep tick`/mem bs=1 count=1 skip=$(( 0x10020036 )) 2>/dev/null | xxd >> 0000000: 00 . >> >> Signed-off-by: Ravi Bangoria >> --- >> kernel/trace/trace_uprobe.c | 105 +++++++++++++++++++++++++++++++++++++++++++- >> 1 file changed, 103 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c >> index b6c9b48..9bf3f7a 100644 >> --- a/kernel/trace/trace_uprobe.c >> +++ b/kernel/trace/trace_uprobe.c >> @@ -50,6 +50,11 @@ struct trace_uprobe_filter { >> struct list_head perf_events; >> }; >> >> +struct sdt_mm_list { >> + struct mm_struct *mm; >> + struct sdt_mm_list *next; >> +}; > Oh, please use struct list_head instead of defining your own pointer-chain :( Sure, will change it. >> + >> /* >> * uprobe event core functions >> */ >> @@ -61,6 +66,8 @@ struct trace_uprobe { >> char *filename; >> unsigned long offset; >> unsigned long ref_ctr_offset; >> + struct sdt_mm_list *sml; >> + struct rw_semaphore sml_rw_sem; > BTW, is there any reason to use rw_semaphore? (mutex doesn't fit?) Hmm.. No specific reason.. will use a mutex instead. Thanks for the review :) Ravi