interconnect fixes for v6.9-rc
Here are fixes for two reported issues. One of them is a fix for
a driver that tries to access a non-existent resource which prints
a warning message during boot. The other one is fixing a race
condition in the core framework where one struct member has been
left unprotected by mutex.
- interconnect: qcom: x1e80100: Remove inexistent ACV_PERF BCM
- interconnect: Don't access req_list while it's being manipulated
Signed-off-by: Georgi Djakov <djakov@kernel.org>
interconnect: Don't access req_list while it's being manipulated
The icc_lock mutex was split into separate icc_lock and icc_bw_lock
mutexes in [1] to avoid lockdep splats. However, this didn't adequately
protect access to icc_node::req_list.
The icc_set_bw() function will eventually iterate over req_list while
only holding icc_bw_lock, but req_list can be modified while only
holding icc_lock. This causes races between icc_set_bw(), of_icc_get(),
and icc_put().
Example A:
CPU0 CPU1
---- ----
icc_set_bw(path_a)
mutex_lock(&icc_bw_lock);
icc_put(path_b)
mutex_lock(&icc_lock);
aggregate_requests()
hlist_for_each_entry(r, ...
hlist_del(...
<r = invalid pointer>
Example B:
CPU0 CPU1
---- ----
icc_set_bw(path_a)
mutex_lock(&icc_bw_lock);
path_b = of_icc_get()
of_icc_get_by_index()
mutex_lock(&icc_lock);
path_find()
path_init()
aggregate_requests()
hlist_for_each_entry(r, ...
hlist_add_head(...
<r = invalid pointer>
Fix this by ensuring icc_bw_lock is always held before manipulating
icc_node::req_list. The additional places icc_bw_lock is held don't
perform any memory allocations, so we should still be safe from the
original lockdep splats that motivated the separate locks.
[1] commit af42269c3523 ("interconnect: Fix locking for runpm vs reclaim")
Signed-off-by: Mike Tipton <quic_mdtipton@quicinc.com>
Fixes: af42269c3523 ("interconnect: Fix locking for runpm vs reclaim")
Reviewed-by: Rob Clark <robdclark@chromium.org>
Link: https://lore.kernel.org/r/20240305225652.22872-1-quic_mdtipton@quicinc.com
Signed-off-by: Georgi Djakov <djakov@kernel.org>
1 file changed
