From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 27 Nov 2018 07:52:13 -0800 From: Sean Christopherson Subject: Re: [PATCH] mm: warn only once if page table misaccounting is detected Message-ID: <20181127155213.GB27075@linux.intel.com> References: <20181127083603.39041-1-heiko.carstens@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181127083603.39041-1-heiko.carstens@de.ibm.com> Sender: owner-linux-mm@kvack.org List-Archive: List-Post: To: Heiko Carstens Cc: Andrew Morton , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, linux-mm@kvack.org, "Kirill A . Shutemov" , Martin Schwidefsky List-ID: On Tue, Nov 27, 2018 at 09:36:03AM +0100, Heiko Carstens wrote: > Use pr_alert_once() instead of pr_alert() if page table misaccounting > has been detected. > > If this happens once it is very likely that there will be numerous > other occurrence as well, which would flood dmesg and the console with > hardly any added information. Therefore print the warning only once. > > Cc: Kirill A. Shutemov > Cc: Martin Schwidefsky > Signed-off-by: Heiko Carstens > --- > kernel/fork.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/fork.c b/kernel/fork.c > index 07cddff89c7b..c887e9eba89f 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -647,8 +647,8 @@ static void check_mm(struct mm_struct *mm) > } > > if (mm_pgtables_bytes(mm)) > - pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", > - mm_pgtables_bytes(mm)); > + pr_alert_once("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", > + mm_pgtables_bytes(mm)); I found the print-always behavior to be useful when developing a driver that mucked with PTEs directly via vmf_insert_pfn() and had issues with racing against exit_mmap(). It was nice to be able to recompile only the driver and rely on dmesg to let me know when I messed up yet again. Would pr_alert_ratelimited() suffice? > #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS > VM_BUG_ON_MM(mm->pmd_huge_pte, mm); > -- > 2.16.4 >