Upstream: https://github.com/makedumpfile/makedumpfile.git
Conflict: none
Resolves: RHEL-88006
Resolves: RHEL-93694
commit 65bf4c9ef0fd0cbf2fb99b60e15b00d984b391b8
Author: Tao Liu <ltao@redhat.com>
Date: Wed Jun 25 14:23:44 2025 +1200
[PATCH v2] Fix a data race in multi-threading mode (--num-threads=N)
A vmcore corrupt issue has been noticed in powerpc arch [1]. It can be
reproduced with upstream makedumpfile.
When analyzing the corrupt vmcore using crash, the following error
message will output:
crash: compressed kdump: uncompress failed: 0
crash: read error: kernel virtual address: c0001e2d2fe48000 type:
"hardirq thread_union"
crash: cannot read hardirq_ctx[930] at c0001e2d2fe48000
crash: compressed kdump: uncompress failed: 0
If the vmcore is generated without num-threads option, then no such
errors are noticed.
With --num-threads=N enabled, there will be N sub-threads created. All
sub-threads are producers which responsible for mm page processing, e.g.
compression. The main thread is the consumer which responsible for
writing the compressed data into file. page_flag_buf->ready is used to
sync main and sub-threads. When a sub-thread finishes page processing,
it will set ready flag to be FLAG_READY. In the meantime, main thread
looply check all threads of the ready flags, and break the loop when
find FLAG_READY.
page_flag_buf->ready is read/write by main/sub-threads simultaneously,
but it is unprotected and unsafe. I have tested both mutex and atomic_rw
can fix this issue. This patch takes atomic_rw for its simplicity.
[1]: https://github.com/makedumpfile/makedumpfile/issues/15
Resolves: https://github.com/makedumpfile/makedumpfile/issues/15
Tested-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Signed-off-by: Tao Liu <ltao@redhat.com>
Signed-off-by: Tao Liu <ltao@redhat.com>
