From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 28 Jun 2012 09:13:52 +1000 From: Anton Blanchard To: Benjamin Herrenschmidt Subject: [PATCH] powerpc: check_and_cede_processor never cedes Message-ID: <20120628091352.48d3859d@kryten> In-Reply-To: <1340837479.3732.90.camel@pasglop> References: <20120628084509.4caec81d@kryten> <1340837479.3732.90.camel@pasglop> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Cc: linuxppc-dev@lists.ozlabs.org, paulus@samba.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi, > I'd rather add a helper, something like lazy_irq_pending() > and hide the actual check for the bits in irq_happened, in > case we change the scheme again. Good idea. Look ok? -- Commit f948501b36c6 ("Make hard_irq_disable() actually hard-disable interrupts") caused check_and_cede_processor to stop working. ->irq_happened will never be zero right after a hard_irq_disable so the compiler removes the call to cede_processor completely. The bug was introduced back in the lazy interrupt handling rework of 3.4 but was hidden until recently because hard_irq_disable did nothing. This issue will eventually appear in 3.4 stable since the hard_irq_disable fix is marked stable, so mark this one for stable too. Signed-off-by: Anton Blanchard Cc: stable@vger.kernel.org --- v2: create a helper, suggested by Ben. Index: linux-build/arch/powerpc/platforms/pseries/processor_idle.c =================================================================== --- linux-build.orig/arch/powerpc/platforms/pseries/processor_idle.c 2012-06-28 08:55:09.422198154 +1000 +++ linux-build/arch/powerpc/platforms/pseries/processor_idle.c 2012-06-28 08:57:36.112591023 +1000 @@ -106,7 +106,7 @@ static void check_and_cede_processor(voi * we first hard disable then check. */ hard_irq_disable(); - if (get_paca()->irq_happened == 0) + if (!lazy_irq_pending()) cede_processor(); } Index: linux-build/arch/powerpc/include/asm/hw_irq.h =================================================================== --- linux-build.orig/arch/powerpc/include/asm/hw_irq.h 2012-06-21 09:16:26.265354429 +1000 +++ linux-build/arch/powerpc/include/asm/hw_irq.h 2012-06-28 08:59:22.082320381 +1000 @@ -103,6 +103,11 @@ static inline void hard_irq_disable(void /* include/linux/interrupt.h needs hard_irq_disable to be a macro */ #define hard_irq_disable hard_irq_disable +static inline bool lazy_irq_pending(void) +{ + return !!(get_paca()->irq_happened & ~PACA_IRQ_HARD_DIS); +} + /* * This is called by asynchronous interrupts to conditionally * re-enable hard interrupts when soft-disabled after having