Messages in this thread | | | Date | Sun, 12 Oct 2008 16:53:06 +0300 | From | Török Edwin <> | Subject | Re: [PATCH 1/4] Add support for userspace stacktraces in tracing/iter_ctrl |
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On 2008-10-12 16:31, Frédéric Weisbecker wrote: > 2008/10/12 Török Edwin <edwintorok@gmail.com>: > >> +static int copy_stack_frame(const void __user *fp, struct stack_frame *frame) >> +{ >> + int ret; >> + >> + if (!access_ok(VERIFY_READ, fp, sizeof(*frame))) >> + return 0; >> + >> + ret = 1; >> + pagefault_disable(); >> + if (__copy_from_user_inatomic(frame, fp, sizeof(*frame))) >> + ret = 0; >> + pagefault_enable(); >> + >> + return ret; >> +} >> + >> > > Hello Török, > > I don't understand why you are using this pagefault disabling and > atomic copy here. > Wouldn't a simple copy_from_user actually take of this? You don't seem > to be in atomic > context. >
Hello,
This function is called from ftrace, as such I could be holding a spinlock. It can also be called from __rwsem_do_wake, which takes a spinlock. This code is from sysprof's copy_stack_frame. Maybe pagefault_disable() is not needed.
Best regards, --Edwin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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