When I combined kgdboc_earlycon with an inflight patch titled ("soc: qcom-geni-se: Add interconnect support to fix earlycon crash") [1] things went boom. Specifically I got a crash during the transition between kgdboc_earlycon and the main kgdboc that looked like this: Call trace: __schedule_bug+0x68/0x6c __schedule+0x75c/0x924 schedule+0x8c/0xbc schedule_timeout+0x9c/0xfc do_wait_for_common+0xd0/0x160 wait_for_completion_timeout+0x54/0x74 rpmh_write_batch+0x1fc/0x23c qcom_icc_bcm_voter_commit+0x1b4/0x388 qcom_icc_set+0x2c/0x3c apply_constraints+0x5c/0x98 icc_set_bw+0x204/0x3bc icc_put+0x30/0xf8 geni_remove_earlycon_icc_vote+0x6c/0x9c qcom_geni_serial_earlycon_exit+0x10/0x1c kgdboc_earlycon_deinit+0x38/0x58 kgdb_register_io_module+0x11c/0x194 configure_kgdboc+0x108/0x174 kgdboc_probe+0x38/0x60 platform_drv_probe+0x90/0xb0 really_probe+0x130/0x2fc ... The problem was that we were holding the "kgdb_registration_lock" while calling into code that didn't expect to be called in spinlock context. Let's slightly defer when we call the deinit code so that it's not done under spinlock. NOTE: this does mean that the "deinit" call of the old kgdb IO module is now made _after_ the init of the new IO module, but presumably that's OK. [1] https://lkml.kernel.org/r/1588919619-21355-3-git-send-email-akashast@codeaurora.org
Showing the changes to kernel/debug/debug_core.c (1 of 1 file). Show all
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| @@ -1089,7 +1089,6 @@ int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops) · 1088 unmodified lines | |||
| 1089 | } | 1089 | } |
| 1090 | pr_info("Replacing I/O driver %s with %s\n", | 1090 | pr_info("Replacing I/O driver %s with %s\n", |
| 1091 | old_dbg_io_ops->name, new_dbg_io_ops->name); | 1091 | old_dbg_io_ops->name, new_dbg_io_ops->name); |
| 1092 | old_dbg_io_ops->deinit(); | ||
| 1093 | } | 1092 | } |
| 1094 | 1093 | ||
| 1095 | if (new_dbg_io_ops->init) { | 1094 | if (new_dbg_io_ops->init) { |
| @@ -1104,8 +1103,10 @@ int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops) · 8 unmodified lines | |||
| 1104 | 1103 | ||
| 1105 | spin_unlock(&kgdb_registration_lock); | 1104 | spin_unlock(&kgdb_registration_lock); |
| 1106 | 1105 | ||
| 1107 | if (old_dbg_io_ops) | 1106 | if (old_dbg_io_ops) { |
| 1107 | old_dbg_io_ops->deinit(); | ||
| 1108 | return 0; | 1108 | return 0; |
| 1109 | } | ||
| 1109 | 1110 | ||
| 1110 | pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name); | 1111 | pr_info("Registered I/O driver %s\n", new_dbg_io_ops->name); |
| 1111 | 1112 | ||