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Fri, 15 Nov 2024 11:02:27 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id cSv9FkMqN2cdYwAAD6G6ig (envelope-from ); Fri, 15 Nov 2024 11:02:27 +0000 Message-ID: <3727258a-7caf-4f05-b8a9-20ab82ee4ea0@suse.cz> Date: Fri, 15 Nov 2024 12:02:27 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/1] sched/numa: Fix memory leak due to the overwritten vma->numab_state To: Raghavendra K T , Adrian Huang , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot Cc: Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Andrew Morton , linux-kernel@vger.kernel.org, Adrian Huang , Jiwei Sun , "linux-mm@kvack.org" References: <20241113102146.2384-1-ahuang12@lenovo.com> <1c8e478d-866a-440e-a11f-80fd210cc5ca@amd.com> Content-Language: en-US From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Score: -4.30 X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-0.997]; MIME_GOOD(-0.10)[text/plain]; TO_DN_EQ_ADDR_SOME(0.00)[]; RCPT_COUNT_TWELVE(0.00)[16]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; MIME_TRACE(0.00)[0:+]; FREEMAIL_TO(0.00)[amd.com,gmail.com,redhat.com,infradead.org,linaro.org]; FUZZY_BLOCKED(0.00)[rspamd.com]; ARC_NA(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; RCVD_TLS_ALL(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; RCVD_VIA_SMTP_AUTH(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[amd.com:email,suse.cz:mid,suse.cz:email,imap1.dmz-prg2.suse.org:helo] X-Spam-Flag: NO X-Spam-Level: On 11/15/24 11:45, Raghavendra K T wrote: > + Vlastimil > > Looks like he was unintentionally missed in CC. He has added Reviewed-by > to V1 Thanks, seems I did it for v1 when v2 was already sent, and without also cc linux-mm I didn't notice it was. > On 11/13/2024 3:51 PM, Adrian Huang wrote: >> From: Adrian Huang >> >> [Problem Description] >> When running the hackbench program of LTP, the following memory leak is >> reported by kmemleak. >> >> # /opt/ltp/testcases/bin/hackbench 20 thread 1000 >> Running with 20*40 (== 800) tasks. >> >> # dmesg | grep kmemleak >> ... >> kmemleak: 480 new suspected memory leaks (see /sys/kernel/debug/kmemleak) >> kmemleak: 665 new suspected memory leaks (see /sys/kernel/debug/kmemleak) >> >> # cat /sys/kernel/debug/kmemleak >> unreferenced object 0xffff888cd8ca2c40 (size 64): >> comm "hackbench", pid 17142, jiffies 4299780315 >> hex dump (first 32 bytes): >> ac 74 49 00 01 00 00 00 4c 84 49 00 01 00 00 00 .tI.....L.I..... >> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >> backtrace (crc bff18fd4): >> [] __kmalloc_cache_noprof+0x2f9/0x3f0 >> [] task_numa_work+0x725/0xa00 >> [] task_work_run+0x58/0x90 >> [] syscall_exit_to_user_mode+0x1c8/0x1e0 >> [] do_syscall_64+0x85/0x150 >> [] entry_SYSCALL_64_after_hwframe+0x76/0x7e >> ... >> >> This issue can be consistently reproduced on three different servers: >> * a 448-core server >> * a 256-core server >> * a 192-core server >> >> [Root Cause] >> Since multiple threads are created by the hackbench program (along with >> the command argument 'thread'), a shared vma might be accessed by two or >> more cores simultaneously. When two or more cores observe that >> vma->numab_state is NULL at the same time, vma->numab_state will be >> overwritten. >> >> Although current code ensures that only one thread scans the VMAs in a >> single 'numa_scan_period', there might be a chance for another thread >> to enter in the next 'numa_scan_period' while we have not gotten till >> numab_state allocation [1]. >> >> Note that the command `/opt/ltp/testcases/bin/hackbench 50 process 1000` >> cannot the reproduce the issue. It is verified with 200+ test runs. >> >> [Solution] >> Use the cmpxchg atomic operation to ensure that only one thread executes >> the vma->numab_state assignment. >> >> [1] https://lore.kernel.org/lkml/1794be3c-358c-4cdc-a43d-a1f841d91ef7@amd.com/ >> >> Fixes: ef6a22b70f6d ("sched/numa: apply the scan delay to every new vma") >> Reported-by: Jiwei Sun >> Signed-off-by: Adrian Huang >> Reviewed-by: Raghavendra K T Reviewed-by: Vlastimil Babka >> --- >> kernel/sched/fair.c | 12 +++++++++--- >> 1 file changed, 9 insertions(+), 3 deletions(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 3356315d7e64..7f99df294583 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -3399,10 +3399,16 @@ static void task_numa_work(struct callback_head *work) >> >> /* Initialise new per-VMA NUMAB state. */ >> if (!vma->numab_state) { >> - vma->numab_state = kzalloc(sizeof(struct vma_numab_state), >> - GFP_KERNEL); >> - if (!vma->numab_state) >> + struct vma_numab_state *ptr; >> + >> + ptr = kzalloc(sizeof(*ptr), GFP_KERNEL); >> + if (!ptr) >> + continue; >> + >> + if (cmpxchg(&vma->numab_state, NULL, ptr)) { >> + kfree(ptr); >> continue; >> + } >> >> vma->numab_state->start_scan_seq = mm->numa_scan_seq; >>