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Vaibhav Jain
ff99d5b6a2
Commit176cda0619("powerpc/perf: Add perf interface to expose vpa counters") introduced 'vpa_pmu' to expose Book3s-HV nested APIv2 provided L1<->L2 context switch latency counters to L1 user-space via perf-events. However the newly introduced PMU named 'vpa_pmu' doesn't assign ownership of the PMU to the module 'vpa_pmu'. Consequently the module 'vpa_pmu' can be unloaded while one of the perf-events are still active, which can lead to kernel oops and panic of the form below on a Pseries-LPAR: BUG: Kernel NULL pointer dereference on read at 0x00000058 <snip> NIP [c000000000506cb8] event_sched_out+0x40/0x258 LR [c00000000050e8a4] __perf_remove_from_context+0x7c/0x2b0 Call Trace: [c00000025fc3fc30] [c00000025f8457a8] 0xc00000025f8457a8 (unreliable) [c00000025fc3fc80] [fffffffffffffee0] 0xfffffffffffffee0 [c00000025fc3fcd0] [c000000000501e70] event_function+0xa8/0x120 <snip> Kernel panic - not syncing: Aiee, killing interrupt handler! Fix this by adding the module ownership to 'vpa_pmu' so that the module 'vpa_pmu' is ref-counted and prevented from being unloaded when perf-events are initialized. Fixes:176cda0619("powerpc/perf: Add perf interface to expose vpa counters") Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com> Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com> Link: https://patch.msgid.link/20250204153527.125491-1-vaibhav@linux.ibm.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.