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3eabed74c0
The `zfs program` subcommand invokes a LUA interpreter to run ZFS "channel programs". This interpreter runs in a constrained environment, with defined memory limits. The LUA stack (used for LUA functions that call each other) is allocated in the kernel's heap, and is limited by the `-m MEMORY-LIMIT` flag and the `zfs_lua_max_memlimit` module parameter. The C stack is used by certain LUA features that are implemented in C. The C stack is limited by `LUAI_MAXCCALLS=20`, which limits call depth. Some LUA C calls use more stack space than others, and `gsub()` uses an unusually large amount. With a programming trick, it can be invoked recursively using the C stack (rather than the LUA stack). This overflows the 16KB Linux kernel stack after about 11 iterations, less than the limit of 20. One solution would be to decrease `LUAI_MAXCCALLS`. This could be made to work, but it has a few drawbacks: 1. The existing test suite does not pass with `LUAI_MAXCCALLS=10`. 2. There may be other LUA functions that use a lot of stack space, and the stack space may change depending on compiler version and options. This commit addresses the problem by adding a new limit on the amount of free space (in bytes) remaining on the C stack while running the LUA interpreter: `LUAI_MINCSTACK=4096`. If there is less than this amount of stack space remaining, a LUA runtime error is generated. Reviewed-by: George Wilson <gwilson@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Ryan Moeller <ryan@ixsystems.com> Reviewed-by: Allan Jude <allanjude@freebsd.org> Reviewed-by: Serapheim Dimitropoulos <serapheim@delphix.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #10611 Closes #10613 |
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| Makefile.am | ||
| perf-regression.run | ||
| sunos.run | ||