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Content-Language: en-US To: Shakeel Butt , Sebastian Andrzej Siewior Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Thomas Gleixner References: <20240528121928.i-Gu7Jvg@linutronix.de> <09e085bb-f09e-4901-a2dd-a0b789bb8a4d@kernel.org> <20240528134027.OxDASsS3@linutronix.de> <20240528141341.rz_rytN_@linutronix.de> From: "Vlastimil Babka (SUSE)" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 8E9F440021 X-Stat-Signature: 7n8orspahe6z48648n6wyjg97bwzoa8o X-HE-Tag: 1716908835-720899 X-HE-Meta: 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 apW8rh// twVYHhIr3b1xj/ge55WEnS46GFuDMflCN9+wYC+pxnBoP9N3RTPAaf4xLiNW3tCQpx71uqfZrxbLC6TfPIJrIuZl8E1sbMy55qX5dQmDGVPv5058lb9SrjXXUaiBvOqflOlT34nePv8OWtrnPc+NFqUZlQ33qzsyz258BNC8NfyMUlZh2rcb2E9nx+FiUmcmEGNxRl9nYzxl9Qia30PnITFKzrjvKIkVM6WbnXx6YIwTR2QcaJcgqf1fMKCOuv3OsZUv2C6e6qGvHKqCB65Y8rtwvXYk1whWxdI8G9dGxXSInX/0G/U86cl3EOqTiixbkK5ZXV+iFQBkTC/0= 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 5/28/24 4:59 PM, Shakeel Butt wrote: > On Tue, May 28, 2024 at 04:13:41PM GMT, Sebastian Andrzej Siewior wrote: >> The assert was introduced in the commit cited below as an insurance that >> the semantic is the same after the local_irq_save() has been removed and >> the function has been made static. >> >> The original requirement to disable interrupt was due the modification >> of per-CPU counters which require interrupts to be disabled because the >> counter update operation is not atomic and some of the counters are >> updated from interrupt context. >> >> All callers of __mod_objcg_mlstate() acquire a lock >> (memcg_stock.stock_lock) which disables interrupts on !PREEMPT_RT and >> the lockdep assert is satisfied. On PREEMPT_RT the interrupts are not >> disabled and the assert triggers. >> >> The safety of the counter update is already ensured by >> VM_WARN_ON_IRQS_ENABLED() which is part of __mod_memcg_lruvec_state() and >> does not require yet another check. > > One question on VM_WARN_ON_IRQS_ENABLED() in __mod_memcg_lruvec_state(). > On a PREEMPT_RT kernel with CONFIG_DEBUG_VM, will that > VM_WARN_ON_IRQS_ENABLED() cause a splat or VM_WARN_ON_IRQS_ENABLED is > special on PREEMPT_RT kernels? It only does something with CONFIG_DEBUG_VM_IRQSOFF and that's disabled by dependencies on PREEMPT_RT :) >> >> Remove the lockdep assert from __mod_objcg_mlstate(). >> >> Fixes: 91882c1617c15 ("memcg: simple cleanup of stats update functions") >> Link: https://lore.kernel.org/r/20240528121928.i-Gu7Jvg@linutronix.de >> Signed-off-by: Sebastian Andrzej Siewior >> --- >> On 2024-05-28 15:44:51 [+0200], Vlastimil Babka (SUSE) wrote: >> > I think just s/memcg_stats_lock()/__mod_memcg_lruvec_state()/ in your >> > phrasing, since we are removing the lockdep assert from path that calls >> > __mod_memcg_lruvec_state() and not memcg_stats_lock()? >> > Or am I missing something? >> >> Yeah, makes sense. >> >> mm/memcontrol.c | 2 -- >> 1 file changed, 2 deletions(-) >> >> --- a/mm/memcontrol.c >> +++ b/mm/memcontrol.c >> @@ -3147,8 +3147,6 @@ static inline void __mod_objcg_mlstate(s >> struct mem_cgroup *memcg; >> struct lruvec *lruvec; >> >> - lockdep_assert_irqs_disabled(); >> - >> rcu_read_lock(); >> memcg = obj_cgroup_memcg(objcg); >> lruvec = mem_cgroup_lruvec(memcg, pgdat);