What does errno 91 (ERESTART) in Solaris mean?

ERESTART

Internal syscall restart state

ERESTART is Solaris errno 91 (Restartable system call). Solaris uses this not-externally-visible value when an interrupted system call should be restarted.

Application code should rarely depend on this internal restart value directly. Diagnose the original signal and system call, then let the Solaris syscall or library restart rules determine whether the operation is reissued or surfaced as an interruption.

What to check

• Ordinary application code should normally see EINTR or a restarted call rather than this errno.
• If tracing shows this errno, inspect signal handling and syscall restart flags.
• Do not expose it as a stable application-level protocol error.

References

• Oracle Solaris intro(2): error numbers
• illumos errno.h definitions
• POSIX errno.h