On Tue, Jul 28, 2026 at 04:00:14PM +0100, James Clark wrote:
Perf's etm_setup_aux() calls cscfg_activate_config() and dereferences cscfg_mgr, which can be done after coresight_init() has initialized the Perf PMU but before cscfg_init() has finished while the driver is still loading.
For this patch, if Perf PMU is dependent on cscfg, why we cannot adjust the init sequence that first call cscfg_init(), then register cs_etm PMU event?
In _cscfg_activate_config(), I can see it dereferences cscfg_mgr:
if (cscfg_mgr->load_state == CSCFG_UNLOAD)
This patch does not check if cscfg_mgr is set. If we try to check cscfg_mgr every time before dereferences it, this approach is quite fragile.
Fix it by only assuming cscfg is initialized if cscfg_mgr is set.
Reported-by: sashiko-bot sashiko-bot@kernel.org Fixes: a0114b4740dd ("coresight: etm-perf: Update to activate selected configuration") Signed-off-by: James Clark james.clark@linaro.org
drivers/hwtracing/coresight/coresight-syscfg.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c index 2bfdd7b45e49..475e8fefa100 100644 --- a/drivers/hwtracing/coresight/coresight-syscfg.c +++ b/drivers/hwtracing/coresight/coresight-syscfg.c @@ -581,7 +581,7 @@ int cscfg_load_config_sets(struct cscfg_config_desc **config_descs, int err = 0; mutex_lock(&cscfg_mutex);
- if (cscfg_mgr->load_state != CSCFG_NONE) {
- if (!cscfg_mgr || cscfg_mgr->load_state != CSCFG_NONE) { mutex_unlock(&cscfg_mutex); return -EBUSY;
If cscfg_mgr is NULL, would directly bail out? This can avoid adding check for every dereference.
Thanks, Leo
P.S. For me, this kind of rare race condition reported by Sashiko can sometimes distract from the main issue. Trying to address it in the same series may mix different issues together. I miss the simpler approach where issues could be resolved with clear boundary.