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authorDouglas Anderson <dianders@chromium.org>2020-05-27 00:20:06 +0300
committerDaniel Thompson <daniel.thompson@linaro.org>2020-06-02 17:15:45 +0300
commitb1350132fef7e1f0ddfd5a985d516a6ed7a329fc (patch)
treeab72a18e652011163b2c8800f312d9e9375396a2 /Documentation/dev-tools/kgdb.rst
parent1feb48baf2fb2aff02aa734c04a3ba5c3297d2de (diff)
downloadlinux-b1350132fef7e1f0ddfd5a985d516a6ed7a329fc.tar.xz
kgdb: Don't call the deinit under spinlock
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 Fixes: 220995622da5 ("kgdboc: Add kgdboc_earlycon to support early kgdb using boot consoles") Signed-off-by: Douglas Anderson <dianders@chromium.org> Link: https://lore.kernel.org/r/20200526142001.1.I523dc33f96589cb9956f5679976d402c8cda36fa@changeid [daniel.thompson@linaro.org: Resolved merge issues by hand] Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
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