From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f44.google.com (mail-pa0-f44.google.com [209.85.220.44]) by kanga.kvack.org (Postfix) with ESMTP id BD0B86B0036 for ; Fri, 23 May 2014 14:34:57 -0400 (EDT) Received: by mail-pa0-f44.google.com with SMTP id ld10so4442894pab.31 for ; Fri, 23 May 2014 11:34:57 -0700 (PDT) Received: from smtp.codeaurora.org (smtp.codeaurora.org. [198.145.11.231]) by mx.google.com with ESMTPS id tc9si978836pbc.52.2014.05.23.11.34.56 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 23 May 2014 11:34:56 -0700 (PDT) From: Mitchel Humpherys Subject: Re: [PATCH] staging: ion: WARN when the handle kmap_cnt is going to wrap around References: <1400806281-32716-1-git-send-email-mitchelh@codeaurora.org> Date: Fri, 23 May 2014 11:34:59 -0700 In-Reply-To: (Colin Cross's message of "Thu, 22 May 2014 18:09:11 -0700") Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: Colin Cross , Greg Kroah-Hartman , devel@driverdev.osuosl.org Cc: Linux-MM , John Stultz , Android Kernel Team , lkml ++greg-kh and devel@driverdev.osuosl.org (my bad for missing you the first time around) On Thu, May 22 2014 at 06:09:11 PM, Colin Cross wrote: > On Thu, May 22, 2014 at 5:51 PM, Mitchel Humpherys > wrote: >> There are certain client bugs (double unmap, for example) that can cause >> the handle->kmap_cnt (an unsigned int) to wrap around from zero. This >> causes problems when the handle is destroyed because we have: >> >> while (handle->kmap_cnt) >> ion_handle_kmap_put(handle); >> >> which takes a long time to complete when kmap_cnt starts at ~0 and can >> result in a watchdog timeout. >> >> WARN and bail when kmap_cnt is about to wrap around from zero. >> >> Signed-off-by: Mitchel Humpherys >> --- >> drivers/staging/android/ion/ion.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c >> index 3d5bf14722..f55f61a4cc 100644 >> --- a/drivers/staging/android/ion/ion.c >> +++ b/drivers/staging/android/ion/ion.c >> @@ -626,6 +626,10 @@ static void ion_handle_kmap_put(struct ion_handle *handle) >> { >> struct ion_buffer *buffer = handle->buffer; >> >> + if (!handle->kmap_cnt) { >> + WARN(1, "%s: Double unmap detected! bailing...\n", __func__); >> + return; >> + } >> handle->kmap_cnt--; >> if (!handle->kmap_cnt) >> ion_buffer_kmap_put(buffer); >> -- >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, >> hosted by The Linux Foundation >> >> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. > > Acked-by: Colin Cross -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org