On Fri, Nov 6, 2009 at 12:45 AM, HU TAO-TGHK48 <taohu@xxxxxxxxxxxx> wrote: > > Any new comments? > > -Hu Tao > > I am happy with this version. Regards, Venkatraman. > >> -----Original Message----- >> From: linux-omap-owner@xxxxxxxxxxxxxxx >> [mailto:linux-omap-owner@xxxxxxxxxxxxxxx] On Behalf Of HU TAO-TGHK48 >> Sent: Saturday, October 31, 2009 5:33 AM >> To: Venkatraman S >> Cc: linux-omap@xxxxxxxxxxxxxxx; Tony Lindgren; Yang >> Fei-AFY095; jon-hunter@xxxxxx; Zhou Ming-a17711; Ye Yuan.Bo-A22116 >> Subject: RE: [PATCH] Fix race condition in omap_request_dma() >> >> Hi, Venkatraman >> >> Agree with you. And just found omap_free_dma() need to be fixed too. >> New patch attached. >> >> From 7aa22ece591365c2dcd73c799d93781497322ff1 Mon Sep 17 00:00:00 2001 >> From: Tao Hu <taohu@xxxxxxxxxxxx> >> Date: Fri, 30 Oct 2009 16:24:25 -0500 >> Subject: [PATCH] Fix race condition in omap dma driver >> >> The bug could cause irq enable bit of one DMA channel is >> cleared/set unexpectedly when 2 (or more) drivers are calling >> omap_request_dma()/omap_free_dma() simultaneously >> >> Signed-off-by: Fei Yang <AFY095@xxxxxxxxxxxx> >> Signed-off-by: Tao Hu <taohu@xxxxxxxxxxxx> >> --- >> arch/arm/plat-omap/dma.c | 6 ++++++ >> 1 files changed, 6 insertions(+), 0 deletions(-) >> >> diff --git a/arch/arm/plat-omap/dma.c >> b/arch/arm/plat-omap/dma.c index cd53b28..5767899 100755 >> --- a/arch/arm/plat-omap/dma.c >> +++ b/arch/arm/plat-omap/dma.c >> @@ -673,13 +673,16 @@ static inline void disable_lnk(int lch) >> static inline void omap2_enable_irq_lch(int lch) { >> u32 val; >> + unsigned long flags; >> >> if (!cpu_class_is_omap2()) >> return; >> >> + spin_lock_irqsave(&dma_chan_lock, flags); >> val = dma_read(IRQENABLE_L0); >> val |= 1 << lch; >> dma_write(val, IRQENABLE_L0); >> + spin_unlock_irqrestore(&dma_chan_lock, flags); >> } >> >> int omap_request_dma(int dev_id, const char *dev_name, @@ >> -788,10 +791,13 @@ void omap_free_dma(int lch) >> >> if (cpu_class_is_omap2()) { >> u32 val; >> + >> + spin_lock_irqsave(&dma_chan_lock, flags); >> /* Disable interrupts */ >> val = dma_read(IRQENABLE_L0); >> val &= ~(1 << lch); >> dma_write(val, IRQENABLE_L0); >> + spin_unlock_irqrestore(&dma_chan_lock, flags); >> >> /* Clear the CSR register and IRQ status register */ >> dma_write(OMAP2_DMA_CSR_CLEAR_MASK, CSR(lch)); >> -- >> 1.5.4.3 >> >> >> >> > -----Original Message----- >> > From: Venkatraman S [mailto:svenkatr@xxxxxxxxx] >> > Sent: Saturday, October 31, 2009 1:22 AM >> > To: HU TAO-TGHK48 >> > Cc: linux-omap@xxxxxxxxxxxxxxx; Tony Lindgren; Yang Fei-AFY095; >> > jon-hunter@xxxxxx; Zhou Ming-a17711; Ye Yuan.Bo-A22116 >> > Subject: Re: [PATCH] Fix race condition in omap_request_dma() >> > >> > On Fri, Oct 30, 2009 at 9:00 AM, HU TAO-TGHK48 <taohu@xxxxxxxxxxxx> >> > wrote: >> > > From a36dac7ee6140ffa23f0adc024964aaf3e266e5f Mon Sep 17 >> > 00:00:00 2001 >> > > From: Tao Hu <taohu@xxxxxxxxxxxx> >> > > Date: Thu, 29 Oct 2009 17:17:21 -0500 >> > > Subject: [PATCH] Fix race condition in omap_request_dma() >> > > >> > > The bug could cause irq enable bit of one DMA channel is cleared >> > > unexpectedly when 2 (or more) drivers are calling >> > > omap_request_dma() simultaneously >> > > >> > > Signed-off-by: Fei Yang <AFY095@xxxxxxxxxxxx> >> > > Signed-off-by: Tao Hu <taohu@xxxxxxxxxxxx> >> > > --- >> > > arch/arm/plat-omap/dma.c | 2 ++ >> > > 1 files changed, 2 insertions(+), 0 deletions(-) >> > > >> > > diff --git a/arch/arm/plat-omap/dma.c >> > b/arch/arm/plat-omap/dma.c index >> > > cd53b28..6895484 100755 >> > > --- a/arch/arm/plat-omap/dma.c >> > > +++ b/arch/arm/plat-omap/dma.c >> > > @@ -749,11 +749,13 @@ int omap_request_dma(int dev_id, const char >> > > *dev_name, >> > > } >> > > >> > > if (cpu_class_is_omap2()) { >> > > + spin_lock_irqsave(&dma_chan_lock, flags); >> > > omap2_enable_irq_lch(free_ch); >> > > omap_enable_channel_irq(free_ch); >> > > /* Clear the CSR register and IRQ status >> register */ >> > > dma_write(OMAP2_DMA_CSR_CLEAR_MASK, CSR(free_ch)); >> > > dma_write(1 << free_ch, IRQSTATUS_L0); >> > > + spin_unlock_irqrestore(&dma_chan_lock, flags); >> > > } >> > >> > Nice catch. I think the lock needs to be applied only for >> the global >> > registers which are changed using the read - update - write method. >> > The dma_write to per channel configuration registers need not be >> > locked. >> > Hence the lock is better placed "within" omap2_enable_irq_lch >> > function. That way, if it's reused, the locking would also be in >> > place. >> > Thank you ! >> > >> -- >> To unsubscribe from this list: send the line "unsubscribe >> linux-omap" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
