d5514013b6
It is possible for a netpoll file to be closed and for the pollDesc to be reused while a netpoll is running. This normally only causes spurious wakeups, but if there is an error on the old file then the new file can be incorrectly marked as having an error. Fix this problem on most systems by introducing an fd sequence field and using that as a tag in a taggedPointer. The taggedPointer is stored in epoll or kqueue or whatever is being used. If the taggedPointer returned by the kernel has a tag that does not match the fd sequence field, the notification is for a closed file, and we can ignore it. We check the tag stored in the pollDesc, and we also check the tag stored in the pollDesc.atomicInfo. This approach does not work on 32-bit systems where the kernel only provides a 32-bit field to hold a user value. On those systems we continue to use the older method without the sequence protection. This is not ideal, but it is not an issue on Linux because the kernel provides a 64-bit field, and it is not an issue on Windows because there are no poller errors on Windows. It is potentially an issue on *BSD systems, but on those systems we already call fstat in newFile in os/file_unix.go to avoid adding non-pollable files to kqueue. So we currently don't know of any cases that will fail. Fixes #59545 Change-Id: I9a61e20dc39b4266a7a2978fc16446567fe683ac Reviewed-on: https://go-review.googlesource.com/c/go/+/484837 Auto-Submit: Ian Lance Taylor <iant@golang.org> Auto-Submit: Ian Lance Taylor <iant@google.com> Run-TryBot: Ian Lance Taylor <iant@golang.org> Reviewed-by: Orlando Labao <orlando.labao43@gmail.com> Reviewed-by: Ian Lance Taylor <iant@google.com> TryBot-Bypass: Ian Lance Taylor <iant@google.com> Reviewed-by: Bryan Mills <bcmills@google.com> TryBot-Bypass: Ian Lance Taylor <iant@golang.org> |
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