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Fri, 01 Aug 2025 07:59:08 -0700 (PDT) Message-ID: <188efc4a8e37bc5dc64dd18989f9a254ef218449.camel@linaro.org> Subject: Re: [PATCH v2 2/6] futex: Use RCU-based per-CPU reference counting instead of rcuref_t From: =?ISO-8859-1?Q?Andr=E9?= Draszik To: Thomas Gleixner , Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org Cc: =?ISO-8859-1?Q?Andr=E9?= Almeida , Darren Hart , Davidlohr Bueso , Ingo Molnar , Juri Lelli , Peter Zijlstra , Valentin Schneider , Waiman Long , Andrew Morton , David Hildenbrand , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , linux-mm@kvack.org Date: Fri, 01 Aug 2025 15:59:06 +0100 In-Reply-To: <87ldo5ihu0.ffs@tglx> References: <87ldo5ihu0.ffs@tglx> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.1-1+build2 MIME-Version: 1.0 X-Stat-Signature: ws7i844ug6ny9gfh611gjm184oq5gozs X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 07A771C000C X-Rspam-User: X-HE-Tag: 1754060350-90421 X-HE-Meta: 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 LwGqIFgB bJcFbcv71JH5HiIEWdm1fWziVUd3EqZrS8+1DVGPcOMxO88SKzmL9UIqntrLOs0geNBw54Qd3EkoSfHaC+Pi2NQH2SrP1cd3Oz+Y21OrZoXpd7VpT2844h5Mi4TUxi3jKB0o7RJsgj+wyRMwRTVb9zVGSstzNrejYgIKKqKS/yapcdpBcYHAWHJ84X+GODrJTblFDOf+xl/Ib2EYqIuQWjnASlZe2g2tYQndWJaVt5kAKdrvmmeJyvh7q5ErTRXlZcCqdBX1lLNzA6Jj4+3YmBOb+Zw+ae63Yf1ib3CmdK3KTydxLKQ9YEoOK5+gL8PfmtEgaQ5hRXpOLumD73SGuhzFWOvG2qrUczj8i X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 2025-07-30 at 21:44 +0200, Thomas Gleixner wrote: > On Wed, Jul 30 2025 at 13:20, Andr=C3=A9 Draszik wrote: > > kmemleak complains about a new memleak with this commit: > >=20 > > [=C2=A0 680.179004][=C2=A0 T101] kmemleak: 1 new suspected memory leaks= (see /sys/kernel/debug/kmemleak) > >=20 > > $ cat /sys/kernel/debug/kmemleak > > unreferenced object (percpu) 0xc22ec0eface8 (size 4): > > =C2=A0 comm "swapper/0", pid 1, jiffies 4294893115 > > =C2=A0 hex dump (first 4 bytes on cpu 7): > > =C2=A0=C2=A0=C2=A0 01 00 00 00=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 .... > > =C2=A0 backtrace (crc b8bc6765): > > =C2=A0=C2=A0=C2=A0 kmemleak_alloc_percpu+0x48/0xb8 > > =C2=A0=C2=A0=C2=A0 pcpu_alloc_noprof+0x6ac/0xb68 > > =C2=A0=C2=A0=C2=A0 futex_mm_init+0x60/0xe0 > > =C2=A0=C2=A0=C2=A0 mm_init+0x1e8/0x3c0 > > =C2=A0=C2=A0=C2=A0 mm_alloc+0x5c/0x78 > > =C2=A0=C2=A0=C2=A0 init_args+0x74/0x4b0 > > =C2=A0=C2=A0=C2=A0 debug_vm_pgtable+0x60/0x2d8 > >=20 > > Reverting this commit (and patches 3 and 4 in this series due to contex= t), > > makes kmemleak happy again. >=20 > Unsurprisingly ... >=20 > debug_vm_pgtable() allocates it via mm_alloc() -> mm->init() and then > after the selftest it invokes mmdrop(), which does not free it, as it is > only freed in __mmput(). >=20 > The patch below should fix it. It does. Thanks Thomas! A.