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authorAlexander Shishkin <alexander.shishkin@linux.intel.com>2016-01-19 17:14:29 +0200
committerIngo Molnar <mingo@kernel.org>2016-01-21 18:54:27 +0100
commit45c815f06b80031659c63d7b93e580015d6024dd (patch)
treec50e9636802f65c2e84b6ee9f7cfd4c806594874 /kernel/events
parent0e1eb0a1f5530bd751fe5bd2c62caa470aaa9643 (diff)
perf: Synchronously free aux pages in case of allocation failure
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. Reported-by: Markus Metzger <markus.t.metzger@intel.com> Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: David Ahern <dsahern@gmail.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: vince@deater.net Link: http://lkml.kernel.org/r/1453216469-9509-1-git-send-email-alexander.shishkin@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/ring_buffer.c40
1 files changed, 20 insertions, 20 deletions
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index adfdc0536117..1faad2cfdb9e 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))