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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id i193-20020a0ddfca000000b00583d1fa1fccsm1332554ywe.0.2023.09.01.15.48.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 01 Sep 2023 15:48:35 -0700 (PDT) Date: Fri, 1 Sep 2023 15:48:26 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Mikhail Gavrilov cc: Hugh Dickins , Andrew Morton , Bagas Sanjaya , linux-kernel@vger.kernel.org, linux-mm@kvack.org, regressions@lists.linux.dev Subject: Re: 6.6/regression/bisected - after commit a349d72fd9efc87c8fd1d16d3164752d84a7275b system stopped booting In-Reply-To: Message-ID: <5e4d50d4-978-ce54-e1ae-40f7117dbf3d@google.com> References: <3548ca67-ce58-3bc6-fef5-348b98d7678b@google.com> <98eb1ba4-5bd3-ee7-1a88-47b054dc938@google.com> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="-1463760895-45710664-1693608515=:22700" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---1463760895-45710664-1693608515=:22700 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE On Fri, 1 Sep 2023, Mikhail Gavrilov wrote: > On Fri, Sep 1, 2023 at 2:08=E2=80=AFPM Hugh Dickins wr= ote: > > > > > > Sorry about that, please try this instead, adds EXPORT_SYMBOL(pte_unmap= ). > > >=20 > Thanks, now I have a working kernel builded at commit a349d72fd9ef. >=20 > > I've never used stackdepot before, but I've tried this out in good and > > bad cases, and expect it to work for you, shedding light on where is > > going wrong - machine should boot up fine, and in dmesg you'll find one > > stacktrace between "WARNING: pte_map..." and "End of pte_map..." lines. >=20 > Interesting, I checked twice but I didn't find any entry with > "pte_map" in the kernel log after applying your patch. That was very disappointing: I found it hard to explain, but was thinking of sending you a similar patch, doing the same check on all your 32 CPUs - maybe the stall being on CPU 0 in your photo was accidental. But now I think I have the shameful answer (which studying your dmesg, and the 82328 jiffies at 86 seconds in your photo, did help me towards). That mm/pagewalk fix I put into 6.5 has a grievous oversight (and a video of your failing 6.6 bootup would likely have shown a WARN_ON_ONCE from the underflow in __rcu_read_unlock()). Please revert the debug patch I sent yesterday (or earlier today), please try booting with this one on top of a349d72fd9ef; and if that's successful, then please go back to your original Rawhide tree and apply this on top of that, to confirm that boots to a working system too - thanks. With my apologies, [PATCH] mm/pagewalk: fix bootstopping regression from extra pte_unmap() [ Commit message yet to be written: it's actually something to go to 6.5 stable, to correct i386 CONFIG_HIGHPTE there - though we know of no case where it is actually hit. ] Signed-off-by: Hugh Dickins --- mm/pagewalk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/pagewalk.c b/mm/pagewalk.c index 2022333805d3..9e7d0276c38a 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -58,7 +58,7 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr,= unsigned long end, =09=09=09pte =3D pte_offset_map(pmd, addr); =09=09if (pte) { =09=09=09err =3D walk_pte_range_inner(pte, addr, end, walk); -=09=09=09if (walk->mm !=3D &init_mm) +=09=09=09if (walk->mm !=3D &init_mm && addr < TASK_SIZE) =09=09=09=09pte_unmap(pte); =09=09} =09} else { --=20 2.35.3 ---1463760895-45710664-1693608515=:22700--