From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932341AbcASPRA (ORCPT ); Tue, 19 Jan 2016 10:17:00 -0500 Received: from mga04.intel.com ([192.55.52.120]:32633 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932252AbcASPQv (ORCPT ); Tue, 19 Jan 2016 10:16:51 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,317,1449561600"; d="scan'208";a="893829946" From: Alexander Shishkin To: Peter Zijlstra Cc: Ingo Molnar , linux-kernel@vger.kernel.org, vince@deater.net, eranian@google.com, Arnaldo Carvalho de Melo , Alexander Shishkin Subject: [PATCH] perf: Synchronously free aux pages in case of allocation failure Date: Tue, 19 Jan 2016 17:14:29 +0200 Message-Id: <1453216469-9509-1-git-send-email-alexander.shishkin@linux.intel.com> X-Mailer: git-send-email 2.7.0.rc3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We are currently using asynchronous deallocation in the error path in AUX mmap code, which is unnecessary and also presents a problem for users that wish to probe for the biggest possible buffer size they can get: they'll get -EINVAL on all subsequent attemts to allocate a smaller buffer before the asynchronous deallocation callback frees up the pages from the previous unsuccessful attempt. Currently, gdb does that for allocating AUX buffers for Intel PT traces. More specifically, overwrite mode of AUX pmus that don't support hardware sg (some implementations of Intel PT, for instance) is limited to only one contiguous high order allocation for its buffer and there is no way of knowing its size without trying. This patch changes error path freeing to be synchronous as there won't be any contenders for the AUX pages at that point. Signed-off-by: Alexander Shishkin Reported-by: Markus Metzger --- kernel/events/ring_buffer.c | 40 ++++++++++++++++++++-------------------- 1 file changed, 20 insertions(+), 20 deletions(-) diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index adfdc05361..1faad2cfdb 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -459,6 +459,25 @@ static void rb_free_aux_page(struct ring_buffer *rb, int idx) __free_page(page); } +static void __rb_free_aux(struct ring_buffer *rb) +{ + int pg; + + if (rb->aux_priv) { + rb->free_aux(rb->aux_priv); + rb->free_aux = NULL; + rb->aux_priv = NULL; + } + + if (rb->aux_nr_pages) { + for (pg = 0; pg < rb->aux_nr_pages; pg++) + rb_free_aux_page(rb, pg); + + kfree(rb->aux_pages); + rb->aux_nr_pages = 0; + } +} + int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event, pgoff_t pgoff, int nr_pages, long watermark, int flags) { @@ -547,30 +566,11 @@ out: if (!ret) rb->aux_pgoff = pgoff; else - rb_free_aux(rb); + __rb_free_aux(rb); return ret; } -static void __rb_free_aux(struct ring_buffer *rb) -{ - int pg; - - if (rb->aux_priv) { - rb->free_aux(rb->aux_priv); - rb->free_aux = NULL; - rb->aux_priv = NULL; - } - - if (rb->aux_nr_pages) { - for (pg = 0; pg < rb->aux_nr_pages; pg++) - rb_free_aux_page(rb, pg); - - kfree(rb->aux_pages); - rb->aux_nr_pages = 0; - } -} - void rb_free_aux(struct ring_buffer *rb) { if (atomic_dec_and_test(&rb->aux_refcount)) -- 2.7.0.rc3