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ring-buffer: Have rb_time_cmpxchg() set the msb counter too 

commit 0aa0e5289c upstream.

The rb_time_cmpxchg() on 32-bit architectures requires setting three
32-bit words to represent the 64-bit timestamp, with some salt for
synchronization. Those are: msb, top, and bottom

The issue is, the rb_time_cmpxchg() did not properly salt the msb portion,
and the msb that was written was stale.

Link: https://lore.kernel.org/linux-trace-kernel/20231215084114.20899342@rorschach.local.home

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: f03f2abce4 ("ring-buffer: Have 32 bit time stamps use all 64 bits")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pull/1175/head
Steven Rostedt (Google) 2023-12-15 08:41:14 -05:00 committed by Greg Kroah-Hartman
parent c425a772fc
commit 869aee35cf
1 changed files with 2 additions and 0 deletions
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2
kernel/trace/ring_buffer.c
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@ -727,10 +727,12 @@ static int rb_time_cmpxchg(rb_time_t *t, u64 expect, u64 set)
cnt2 = cnt + 1;
rb_time_split(val, &top, &bottom, &msb);
msb = rb_time_val_cnt(msb, cnt);
top = rb_time_val_cnt(top, cnt);
bottom = rb_time_val_cnt(bottom, cnt);
rb_time_split(set, &top2, &bottom2, &msb2);
msb2 = rb_time_val_cnt(msb2, cnt);
top2 = rb_time_val_cnt(top2, cnt2);
bottom2 = rb_time_val_cnt(bottom2, cnt2);