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Thu, 13 Aug 2026 21:29:07 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:ecab:fe19:825:5aeb]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84fc4565c6bsm1584682b3a.3.2026.08.13.21.29.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 13 Aug 2026 21:29:06 -0700 (PDT) Date: Fri, 14 Aug 2026 13:29:02 +0900 From: Sergey Senozhatsky To: Barry Song Cc: Sergey Senozhatsky , akpm@linux-foundation.org, bigeasy@linutronix.de, hdanton@sina.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, minchan@kernel.org, ryncsn@gmail.com, yosry.ahmed@linux.dev, surenb@google.com, Dongdong Zhang Subject: Re: [RFC PATCH] zram: avoid preemption with CPU-based compression backends Message-ID: References: <20260805005545.66112-1-baohua@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Stat-Signature: f14o86xgjzbmmpbkn43e4r19gubiqtar X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 7024040008 X-HE-Tag: 1786681748-498415 X-HE-Meta: U2FsdGVkX1+QMU5HlbkK+WRX+vdgSKLimpC8oHStRkgSXu2h8pEl4HQPVbmgXbYsj+QodqmbrsSUX8q5NOC7ToLEmro8ZiigG5XtbYrUjCzfZswoM6QdlqbXqsyqKTrSet/MeIdoUk/nQks0DVfHE7EkqjwHJTIVPuPwqkkIlqp0x45eh8Pty2HmfnnB+OqTwZU3RTL/HNra0a8Wf5F97ip5/MJPpspM2qQQicF20wfBiHfU18pzjNThQ1cwF5iOufP/XfAY+b6RijPjOLfywuAgt4BRohHA+jyReZPfGcBsyMcu5lRqjzYTuyyiGrCmjjDyHXTYUn0opygxMgtt8NpFAtRZzXyFUdt7wEe3audl8C1I6F0U4/2doL/g5vl5IMN6KeiwC0NjzIopQ4ZRbYKRHpp7JUa7oMdmy+fYDLbuDSpRy0GjbgcZvO8lxrrvbB8xD8a/eFHbqUoZ9Au74A6GjoMlUeNigvcpK/UZBokIXXeP8iNfTnYOQht0hHrmA3r79n+BGKQsUI3yDjlBmh8myq2pFdI6Dpf+7PHNYyx/74Hqs8MJQPzeUMiHrq4cXqluji12ZLBUj933m5uulSk3LAcUtKIRcfExkyJeHHevCS6Wf63ch1IE6ZS5hHacOHhczCveQEvzegwrS1hUIfV/iQHcCiY+fDY4HCUtQu10weKXH9NgDyjI4W3oE85lD+hZGb8AzBkZvrjBFaNHUkrpGJ4bgZjc5yGZ53f/o2Z8chnEuzmdJzBy2T83RiNMjD7WJEYiJKTfoXa9/dFQiUvc61CwglbQsHoBkg2FHCzXo+UOTSuZawoo7O3wurgfsNo2zHcpk4GDG0Hrd5IbrslwivsCIEbrwGoqoOQEuF0rLGS73PSu/Pa7s8Um8QGGVT+m+BNMM9LByx+MKTAyuJER3Ve5S5r8HaNX2ULAFs21/Dhb0SmDePxHOi+AujZGcK/gNXdJp/X69iG7Sfa AcCcXrWz d+xqKIiQjuSXqdCdWY48vVooE2e/tsNMdOh0GzpFg1h2MNyFHe3Ez78ritOCjOMUd1/ODtQ6Cod/SIXcUIfQfExWNK3+MzoP9RLD8NPvGe+eTn9VoDSbBn9e49TMUXCapdg/hEoIweX4rk1IyrmWEuAwz8mchyddP5dpQAKROji+bwqZ1PKOJ3mCohAfivIEEGib4/phycTPJSZE71hiDRn/Uvd+yLnbHXHLSATEQp5ejiLywCumW0OoguD/C5CG1lrsA4O3LcGv7LaC2T/SUGUSIssJaIhVzd9P5tS3lLGhOyxJP4olc4bLfD6B0ZWHDYy2ASccyAqn3vcqLGbEwJzlGPvxXc7eUuxi/bt9V4er1Z3I= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello, On (26/08/14 08:07), Barry Song wrote: > > On (26/08/05 08:55), Barry Song (Xiaomi) wrote: > > > @@ -128,14 +128,20 @@ struct zcomp_strm *zcomp_stream_get(struct zcomp *comp) > > > * so then unlock and re-try on the current CPU. > > > */ > > > mutex_lock(&zstrm->lock); > > > + if (!comp->ops->async && !IS_ENABLED(CONFIG_PREEMPT_RT)) > > > + preempt_disable(); > > > > We take slot_lock(), which is preemptible, under stream lock on > > some paths. > > Hi Sergey, > > As promised in [1], those patches are still under testing on real > Android phones. However, I'm quite curious which path takes > slot_lock while holding the zstream lock Oh, I think you are right. We do the opposite: stream lock under slot lock, and we also do the stream lock -> zsmalloc lock/unlock -> stream unlock -> slot lock/unlock chain. But it doesn't look like we ever do stream lock -> slot lock, you are right. Sorry for the confusion.