Commit a0ad494b authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google) Committed by Peng Zhang
Browse files

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

stable inclusion
from stable-v6.6.8
commit 3432f9686a37a591da81bff73d15da3735e4bac8
bugzilla: https://gitee.com/openeuler/kernel/issues/I99K53

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3432f9686a37a591da81bff73d15da3735e4bac8

--------------------------------

commit 0aa0e5289cfe984a8a9fdd79ccf46ccf080151f7 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: f03f2abc ("ring-buffer: Have 32 bit time stamps use all 64 bits")
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarZhangPeng <zhangpeng362@huawei.com>
parent dd4e9ac5

kernel/trace/ring_buffer.c

+2 −0
Original line number Diff line number Diff line
@@ -729,10 +729,12 @@ static bool 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);