https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=220037
Bug ID: 220037
Summary: [vfs] sys/kern/vfs_bio.c: a sleep-under-rwlock bug in
getblk
Product: Base System
Version: 11.0-RELEASE
Hardware: i386
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: kern
Assignee: [email protected]
Reporter: [email protected]
The kernel may sleep under a rwlock, and the function call path in file
"sys/kern/vfs_bio.c" in FreeBSD 11.0 is:
getblk [line 3498: acquire the rwlock by BO_RLOCK]
bp_unmapped_get_kva [line 3582]
bufspace_wait [line 3430]
buf_flush [line 637] (rw_wunlock(&nblock) is called, but not BO_RUNLOCK)
flushbufqueues [line 2977]
malloc(M_WAITOK) [line 3093] --> may sleep
The possible fix of this bug is to set the last parameter "M_WAITOK" in malloc
to "M_NOWAIT".
This bug is found by a static analysis tool written by myself, and it is
checked by my review of the FreeBSD code.
By the way, I am a freshman in developing FreeBSD drivers, and I am willing to
submit a patch. But I do not know how to write and submit a patch, and where to
submit, so I am looking forward to useful advice :)
Jia-Ju Bai
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