On Mon, 5 Sep 2022 11:23:14 +0800
lijiazi <jqqlijiazi@xxxxxxxxx> wrote:
> >From ramdump, current reader page's commit is 0xff0, not bigger than
> BUF_PAGE_SIZE:
> crash> struct buffer_page 0xffffffd10b599580 -x
> struct buffer_page {
> list = {
> next = 0xffffffd10b599500,
> prev = 0xffffffd10b599680
> },
> write = {
> a = {
> counter = 0x100ff0
> }
> },
> read = 0xfd4,
> entries = {
> a = {
> counter = 0x100053
> }
> },
> real_end = 0xfd4,
> page = 0xffffffd10b553000
> }
> crash> struct buffer_data_page 0xffffffd10b553000 -x
> struct buffer_data_page {
> time_stamp = 0xe2679ca0cd3d,
> commit = {
> a = {
> counter = 0xff0
> }
> },
> data = 0xffffffd10b553010 "\b"
> }
> I also can extrace trace log from ramdump by crash-trace extension tool:
> bsp: <...>-32191 [006] 249032.606401: signal_generate: sig=17 errno=0 code=1 comm=WifiDiagnostics pid=1535 grp=1 res=1
> bsp: <...>-32183 [006] 249032.625192: sched_process_exit: comm=osi_bin pid=32183 prio=120
> bsp: <...>-32196 [006] 249033.677333: sched_process_exit: comm=ip pid=32196 prio=120
> bsp: <...>-32196 [006] 249033.677562: signal_generate: sig=17 errno=0 code=1 comm=sh pid=32195 grp=1 res=0
> Above logs is on reader page, reader task try to read PADDING event
> after this event and lead to crash.
Ah, it's not an issue with the commit value but the write value.
Can you test this patch.
-- Steve
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index d59b6a328b7f..6bf7706bb33b 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -2608,6 +2608,9 @@ rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
/* Mark the rest of the page with padding */
rb_event_set_padding(event);
+ /* Make sure the padding is visible before the write update */
+ smp_wmb();
+
/* Set the write back to the previous setting */
local_sub(length, &tail_page->write);
return;
@@ -4580,6 +4583,13 @@ rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
goto again;
out:
+ /* If the write is past the end of page, a writer is still updating it */
+ if (reader && reader->write > BUF_PAGE_SIZE)
+ reader = NULL;
+
+ /* Make sure we see any padding after the write update */
+ smp_rmb();
+
/* Update the read_stamp on the first event */
if (reader && reader->read == 0)
cpu_buffer->read_stamp = reader->page->time_stamp;
|