> -----Original Message----- > From: Dmitry Torokhov [mailto:dmitry.torok...@gmail.com] > Sent: Thursday, November 07, 2013 8:47 AM > To: Liu, Chuansheng > Cc: t...@kernel.org; Greg KH; linux-kernel@vger.kernel.org > Subject: Re: [PATCH] devres: Freeing the drs after all release() are called > > On Thu, Nov 07, 2013 at 12:36:56AM +0000, Liu, Chuansheng wrote: > > > > > > > -----Original Message----- > > > From: Tejun Heo [mailto:hte...@gmail.com] On Behalf Of t...@kernel.org > > > Sent: Thursday, November 07, 2013 8:30 AM > > > To: Liu, Chuansheng > > > Cc: Greg KH; dmitry.torok...@gmail.com; linux-kernel@vger.kernel.org > > > Subject: Re: [PATCH] devres: Freeing the drs after all release() are > > > called > > > > > > Hello, Liu. > > > > > > On Thu, Nov 07, 2013 at 12:27:56AM +0000, Liu, Chuansheng wrote: > > > > The driver code is as below: > > > > _INIT() { > > > > > > > > A = devm_kzalloc(); > > > > B= devm_request_threaded_irq(isr_handler); > > > > C = devm_kzalloc(); > > > > } > > > > > > > > When driver _EXIT, the devres_release_all () will be called. > > > > The C will be kfreed before B, but when freeing irq B, the pending > isr_handler() > > > possibly > > > > will access the memory B which has been freed. > > > > Then the memory corruption occurred. > > > > > > > > This patch can solve this scenario. > > > > > > Isn't the bug there IRQ being requested before all its resources are > > > allocated? The proposed change just masks the underlying issue or > > > incorrectly ordered operations. > > Yes, I knew I can put the code always like below: > > A = devm_kzalloc(); > > C = devm_kzalloc(); > > ... > > B= devm_request_threaded_irq(isr_handler); > > > > But, the above is just one simple coding prototype, if there are many > > calling: > > E -- > F -- > D -- >... then to devm_kzalloc(). > > > > To be honest, it will make code too hard to always adapt the rule? > > And I trying to find out every potential devm_kzalloc() before irq > > requesting. > > Such code is already broken anyway and has to be fixed - if your IRQ > handler accesses data allocated by devm_kzalloc that you call only > _after_ you called devm_request_irq() then interrupt arriving at > unfortunate moment will crash your driver at the probing stage.
Not exactly, request_irq() does not means the device irq is enabled indeed. After using devres_release_all() to free the device resources, it hiddenly force all drivers probe() to put the request_irq() at the end of probe() function. Moreover, you can not call devres_alloc* again after probe().... Otherwise, there are potential memory corruption. And except for irq related, maybe there are other things. So I just feel this rule is too restricted? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
