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a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1601888154; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=tIhP0FuIGl8w6hVtstWYo1miB0t+IY3lSNHO1NwBAUg=; b=Nn+A19Q+Lozpu8w7R4t0zbn+T9kc7/1vuZQhI5Wg6N3F0nR0r8evtwNibaf602A4ecMxS9 m5hTCF8F9bbSbtAg== To: Ulf Hansson Subject: Re: [PATCH] mmc: meson-gx: remove IRQF_ONESHOT In-Reply-To: References: <20201002164915.938217-1-jbrunet@baylibre.com> Date: Mon, 05 Oct 2020 10:55:54 +0200 Message-ID: <87wo052grp.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201005_045558_095094_49C20896 X-CRM114-Status: GOOD ( 16.54 ) X-BeenThere: linux-amlogic@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Hilman , Sebastian Andrzej Siewior , "linux-mmc@vger.kernel.org" , Linux Kernel Mailing List , "open list:ARM/Amlogic Meson..." , Brad Harper , Jerome Brunet Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org On Mon, Oct 05 2020 at 10:22, Ulf Hansson wrote: > On Fri, 2 Oct 2020 at 18:49, Jerome Brunet wrote: >> >> IRQF_ONESHOT was added to this driver to make sure the irq was not enabled >> again until the thread part of the irq had finished doing its job. >> >> Doing so upsets RT because, under RT, the hardirq part of the irq handler >> is not migrated to a thread if the irq is claimed with IRQF_ONESHOT. >> In this case, it has been reported to eventually trigger a deadlock with >> the led subsystem. >> >> Preventing RT from doing this migration was certainly not the intent, the >> description of IRQF_ONESHOT does not really reflect this constraint: >> >> > IRQF_ONESHOT - Interrupt is not reenabled after the hardirq handler finished. >> > Used by threaded interrupts which need to keep the >> > irq line disabled until the threaded handler has been run. >> >> This is exactly what this driver was trying to acheive so I'm still a bit >> confused whether this is a driver or an RT issue. >> >> Anyway, this can be solved driver side by manually disabling the IRQs >> instead of the relying on the IRQF_ONESHOT. IRQF_ONESHOT may then be removed >> while still making sure the irq won't trigger until the threaded part of >> the handler is done. > > Thomas, may I have your opinion on this one. > > I have no problem to apply $subject patch, but as Jerome also > highlights above - this kind of makes me wonder if this is an RT > issue, that perhaps deserves to be solved in a generic way. > > What do you think? Let me stare at the core code. Something smells fishy. _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic