Description: tracing: Fix race in trace_open and buffer resize call
References:
 https://bugzilla.redhat.com/show_bug.cgi?id=1905155
 https://lore.kernel.org/linux-arm-msm/20200915141304.41fa7c30@gandalf.local.home/
Notes:
 carnil> Commit fixes b23d7a5f4a07a ("ring-buffer: speed up buffer
 carnil> resets by avoiding synchronize_rcu for each CPU") in v5.9-rc1
 carnil> and not backported to other series.
 carnil> Actually it is not the cause of the bug but a commit which
 carnil> should have been "Depends-on", cf. https://lore.kernel.org/stable/20210121140951.2a554a5e@gandalf.local.home/
Bugs:
upstream: released (5.10-rc1) [bbeb97464eefc65f506084fd9f18f21653e01137]
5.10-upstream-stable: N/A "Fixed before branching point"
4.19-upstream-stable: released (4.19.172) [acfa7ad7b7f6489e2bed20880ce090fdabdbb841]
4.9-upstream-stable: released (4.9.254) [04f51df12ddaa0e2a38223da00e0d3ed02d62a01]
sid: released (5.9.6-1)
4.19-buster-security: released (4.19.171-1) [debian/patches/bugfix/all/tracing-fix-race-in-trace_open-and-buffer-resize-call.patch]
4.9-stretch-security: released (4.9.258-1)