Date: Sat, 11 Apr 2026 01:52:41 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 293382] Dead lock and kernel crash around closefp_impl Message-ID: <bug-293382-227-nL2KJWljrx@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-293382-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=293382 Kristofer Peterson <kris@tranception.com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |kris@tranception.com --- Comment #60 from Kristofer Peterson <kris@tranception.com> --- Hi, I don't know if this is related but a while ago I experienced kernel panics under 14.3 and 15.0 on AMD EPYC 9274F and 9375F boxes with 768GB RAM running a multithreaded app with a large number of open files (some sockets but mostly memory mapped files) and a high rate of file descriptor "churn" (mmap'd files are frequently created, written, unmapped and deleted). The panics occurred during fork/exec calls and examination of the crash dumps showed corrupted file tables. When running debug kernels, the one place that has consistently come up in the kernel panics is do_fork/fdcopy/fdgrowtable, where fdgrowtable is repeatedly called to create and expand a file table as other threads in the parent continue to open new files. fdgrowtable repeatedly allocates and copies an ever increasing file table until eventually fdt_nfiles at the start of the growing table is read back inexplicably as zero which fails the KASSERT at the start of fdgrowtable. The file tables are typically in the range of 250k to 500k entries in size when this happens which, given that the entries are 48 bytes in size, means the memory allocations and copies are on the order of several megabytes. I have written a small kernel module and a test program that repeatedly allocates, fills, copies, checks and frees memory which I will shortly attach to this bug report. I have only seen this problem with AMD Zen4 & Zen5 EPYC machines, I have not been able to reproduce this on older CPUs. -- You are receiving this mail because: You are the assignee for the bug.home | help
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