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[24.9.77.57]) by smtp.googlemail.com with ESMTPSA id f8sm1435548ioc.24.2020.11.25.11.37.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Nov 2020 11:37:26 -0800 (PST) From: Jim Cromie To: linux-mm@kvack.org Cc: gregkh@linuxfoundation.org, linux@rasmusvillemoes.dk, Jim Cromie , Jason Baron , linux-kernel@vger.kernel.org Subject: [PATCH 6/7] dyndbg: add locking around zpool-add loop in zpool-init Date: Wed, 25 Nov 2020 12:36:25 -0700 Message-Id: <20201125193626.2266995-7-jim.cromie@gmail.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201125193626.2266995-1-jim.cromie@gmail.com> References: <20201125193626.2266995-1-jim.cromie@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This commit doesnt improve things, last commit was working, next one still breaks, despite this "fix". I keep it separate to isolate it and the reasoning for review, which now stated, will be refuted as needed. ;-) Locking review: ddebug_zpool_init(), like other ddebug_*_init() routines, does no locking itself. Unlike them, it runs later, at late_init. This patch doesnt fix the kernel panic that HEAD+1 does. ddebug_callsite_get/put() are called as a pair under mutex-lock for all 3 callsite users. 2 of them; ddebug_change() and dynamic_emit_prefix(), do their own ABBA-ish LGPU (Lock-Get-Put-Unlock). ddebug_proc_show() does the GP part, and is wrapped by ddebug_proc_start|stop() with LU. ddebug_add_module() does LU to protect list_add(), HEAD~1 added ddebug_zpool_add() loop inside that protection. This commit adds locking to ddebug_zpool_init(), around the loop of ddebug_zpool_add(), to match the locking in ddebug_add_module(). Signed-off-by: Jim Cromie --- lib/dynamic_debug.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c index 473406b069a7..534d73e45844 100644 --- a/lib/dynamic_debug.c +++ b/lib/dynamic_debug.c @@ -1195,8 +1195,10 @@ static void __init ddebug_zpool_init(void) } /* add-module normally does this, but not in time for builtins */ + mutex_lock(&ddebug_lock); for (iter = __start___dyndbg; iter < __stop___dyndbg; iter++) ddebug_zpool_add(iter); + mutex_unlock(&ddebug_lock); v2pr_info("total pages: %lu compaction: %lu\n", zs_get_total_pages(dd_callsite_zpool), -- 2.28.0