From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [patch] x86/efi: use GFP_ATOMIC under spin_lock Date: Sun, 9 Mar 2014 07:48:19 +0100 Message-ID: <20140309064819.GB22561@gmail.com> References: <20140307112055.GE2351@elgon.mountain> <20140307121022.GA32575@gmail.com> <20140307122103.GM4774@mwanda> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20140307122103.GM4774@mwanda> Sender: kernel-janitors-owner@vger.kernel.org To: Dan Carpenter Cc: Matt Fleming , Nathan Zimmer , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-efi@vger.kernel.org, kernel-janitors@vger.kernel.org List-Id: linux-efi@vger.kernel.org * Dan Carpenter wrote: > On Fri, Mar 07, 2014 at 01:10:22PM +0100, Ingo Molnar wrote: > > > > * Dan Carpenter wrote: > > > > > In phys_efi_get_time() we call efi_call_phys_prelog() with a spin_lock > > > so this allocation should be atomic. > > > > > > Fixes: b8f2c21db390 ('efi, x86: Pass a proper identity mapping in efi_call_phys_prelog') > > > Signed-off-by: Dan Carpenter > > > > > > diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c > > > index 0c2a234fef1e..f5adcadb381b 100644 > > > --- a/arch/x86/platform/efi/efi_64.c > > > +++ b/arch/x86/platform/efi/efi_64.c > > > @@ -90,7 +90,7 @@ void __init efi_call_phys_prelog(void) > > > local_irq_save(efi_flags); > > > > > > n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT), PGDIR_SIZE); > > > - save_pgd = kmalloc(n_pgds * sizeof(pgd_t), GFP_KERNEL); > > > + save_pgd = kmalloc(n_pgds * sizeof(pgd_t), GFP_ATOMIC); > > > > > > for (pgd = 0; pgd < n_pgds; pgd++) { > > > save_pgd[pgd] = *pgd_offset_k(pgd * PGDIR_SIZE); > > > > The allocation there, if it happens within a spinlocked path, is > > probably a layering violation - and GFP_ATOMIC is at best a > > workaround. > > > > You're on your own for fixing the complicated stuff like layering > violations. I just do static checker stuff and sed fixes. ;) It's a generic pattern: GFP_KERNEL -> GFP_ATOMIC fixes are almost always wrong. Thanks, Ingo