From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BD97775809 for ; Sat, 7 Dec 2024 04:29:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733545759; cv=none; b=JYALVT8VNWxRXtmwXYRcyTHG/Hl0r9jwArTDH+gtBtPX9kfRi9xpmOfNJE+qaWuW3zGgvXV3n3fyQbyeUQjibt3Q2PsdlXxMkNj+dEWzpfGaTKwQDpNV6KtwyHzM/UOp5s7E69syksQq3BKEZnpDUyUNfi+PshNbcJFlCOVV+Jo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733545759; c=relaxed/simple; bh=yF33xD3T4TDYeqiMgPSwNPCDAJ/seILn3aRgCpPIL7c=; h=Date:To:From:Subject:Message-Id; b=Wsotq2HE1ogJj1NjfRhlTuRYVXnnDSCDLQulCDqeY15qIGfJcqCHygFaHZsYOu59Og9RawN8ORWH/iOLtmGz0YGhMxYmaKjpcTKll3YML96u5gycgMdvX6GQ9rB0zbk/sIHU1ItmyFiKu94gPjNfu7yfgfQ4/IGYjzVk+mQ1+mk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=E4wSlWk4; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="E4wSlWk4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1EAFCC4CECD; Sat, 7 Dec 2024 04:29:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1733545758; bh=yF33xD3T4TDYeqiMgPSwNPCDAJ/seILn3aRgCpPIL7c=; h=Date:To:From:Subject:From; b=E4wSlWk4ABAaiTjYnQqiB2jl+KM9LBQPGBihK4wX6x3BsbjehNeOrbSKVERSKAk6k iXOvOSG2+nfyKheZeMObfZWSt/6Qp//tKXIeLkFStW3ZN5RgRNLcfB/HTFftOakfCq yMDFvchk6njvZuPCrM243UXYwc7ihDpleM9Jer08= Date: Fri, 06 Dec 2024 20:29:17 -0800 To: mm-commits@vger.kernel.org,willy@infradead.org,vbabka@suse.cz,souravpanda@google.com,shakeel.butt@linux.dev,richard.weiyang@gmail.com,peterz@infradead.org,peterx@redhat.com,paulmck@kernel.org,pasha.tatashin@soleen.com,oleg@redhat.com,mjguzik@gmail.com,minchan@google.com,mhocko@suse.com,mgorman@techsingularity.net,lorenzo.stoakes@oracle.com,Liam.Howlett@Oracle.com,jannh@google.com,hughd@google.com,hdanton@sina.com,hannes@cmpxchg.org,dhowells@redhat.com,david@redhat.com,dave@stgolabs.net,corbet@lwn.net,brauner@kernel.org,surenb@google.com,akpm@linux-foundation.org From: Andrew Morton Subject: + seqlock-add-raw_seqcount_try_begin.patch added to mm-unstable branch Message-Id: <20241207042918.1EAFCC4CECD@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: seqlock: add raw_seqcount_try_begin has been added to the -mm mm-unstable branch. Its filename is seqlock-add-raw_seqcount_try_begin.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/seqlock-add-raw_seqcount_try_begin.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Suren Baghdasaryan Subject: seqlock: add raw_seqcount_try_begin Date: Fri, 22 Nov 2024 09:44:14 -0800 Add raw_seqcount_try_begin() to opens a read critical section of the given seqcount_t if the counter is even. This enables eliding the critical section entirely if the counter is odd, instead of doing the speculation knowing it will fail. Link: https://lkml.kernel.org/r/20241122174416.1367052-1-surenb@google.com Signed-off-by: Suren Baghdasaryan Reviewed-by: David Hildenbrand Reviewed-by: Liam R. Howlett Suggested-by: Peter Zijlstra Cc: Christian Brauner Cc: David Howells Cc: Davidlohr Bueso Cc: Hillf Danton Cc: Hugh Dickins Cc: Jann Horn Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Lorenzo Stoakes Cc: Mateusz Guzik Cc: Matthew Wilcox Cc: Mel Gorman Cc: Michal Hocko Cc: Minchan Kim Cc: Oleg Nesterov Cc: Pasha Tatashin Cc: Paul E. McKenney Cc: Peter Xu Cc: Shakeel Butt Cc: Sourav Panda Cc: Vlastimil Babka Cc: Wei Yang Signed-off-by: Andrew Morton --- include/linux/seqlock.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) --- a/include/linux/seqlock.h~seqlock-add-raw_seqcount_try_begin +++ a/include/linux/seqlock.h @@ -319,6 +319,28 @@ SEQCOUNT_LOCKNAME(mutex, struct m }) /** + * raw_seqcount_try_begin() - begin a seqcount_t read critical section + * w/o lockdep and w/o counter stabilization + * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants + * + * Similar to raw_seqcount_begin(), except it enables eliding the critical + * section entirely if odd, instead of doing the speculation knowing it will + * fail. + * + * Useful when counter stabilization is more or less equivalent to taking + * the lock and there is a slowpath that does that. + * + * If true, start will be set to the (even) sequence count read. + * + * Return: true when a read critical section is started. + */ +#define raw_seqcount_try_begin(s, start) \ +({ \ + start = raw_read_seqcount(s); \ + !(start & 1); \ +}) + +/** * raw_seqcount_begin() - begin a seqcount_t read critical section w/o * lockdep and w/o counter stabilization * @s: Pointer to seqcount_t or any of the seqcount_LOCKNAME_t variants _ Patches currently in -mm which might be from surenb@google.com are alloc_tag-fix-module-allocation-tags-populated-area-calculation.patch alloc_tag-fix-set_codetag_empty-when-config_mem_alloc_profiling_debug.patch seqlock-add-raw_seqcount_try_begin.patch mm-convert-mm_lock_seq-to-a-proper-seqcount.patch mm-introduce-mmap_lock_speculate_try_beginretry.patch mm-introduce-vma_start_read_locked_nested-helpers.patch mm-move-per-vma-lock-into-vm_area_struct.patch mm-mark-vma-as-detached-until-its-added-into-vma-tree.patch mm-make-vma-cache-slab_typesafe_by_rcu.patch mm-slab-allow-freeptr_offset-to-be-used-with-ctor.patch docs-mm-document-latest-changes-to-vm_lock.patch