Why semtimedop returns EAGAIN? (Doc ID 2111325.1)

Last updated on JANUARY 15, 2024

Applies to:

Goal

Running truss(1) on a process may show semtimedop(2) return EAGAIN as follows.

44267/1:        semtimedop(234881131, 0xFFFFFFFF7FFFCAF4, 1, 0xFFFFFFFF7FFFCAE0) (sleeping...)
44267/1:                semnum=170   semop=-1    semflg=0
44267/1:                timeout: 5.000000000 sec
44267/1:         7.5196  5.0107  0.0001 semtimedop(234881131, 0xFFFFFFFF7FFFCAF4, 1, 0xFFFFFFFF7FFFCAE0) Err#11 EAGAIN
44267/1:                semnum=170   semop=-1    semflg=0
44267/1:                timeout: 5.000000000 sec

In general, EAGAIN is used as the error code when there is a resource issue. strerror(3C) translates EAGAIN to Resource temporarily unavailable.

However, if the system call is semtimedop(2), EAGAIN does not necessarily mean any resource issue. This can often be mis-diagnosed as an Operating System resource issue.

This document explains the why semtimedop() returns EAGAIN and why, most of the time, it is not necessary Operating System.

Solution

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