> Daniel, any thoughts? Our application of this protocol is only with specific modems to enable circuit switched operation (handling calls, selecting/querying networks, etc.) while doing packet switched communication (i.e. IP traffic over PPP). The protocol was developed for such use cases. Regarding the issue itself: There was already an attempt to fix all this by switching from spinlocks to mutexes resulting in ~20% performance loss. However, the patch was reverted as it did not handle the T1 timer leading into sleep during atomic within gsm_dlci_t1() on every mutex lock there. There was also a suggestion to fix this in do_con_write() as tty_operations::write() appears to be documented as "not allowed to sleep". The patch for this was rejected. It did not fix the issue within n_gsm. Link: https://lore.kernel.org/all/20221203215518.8150-1-pchelkin@xxxxxxxxx/ Link: https://lore.kernel.org/all/20221212023530.2498025-1-zengheng4@xxxxxxxxxx/ Link: https://lore.kernel.org/all/5a994a13-d1f2-87a8-09e4-a877e65ed166@xxxxxxxxxx/ Best regards, Daniel Starke
