linux-kernel - Q.: Why does tty_ioctl.c: set_termios return EINTR instead of ERESTARTSYS?

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Message-ID: <CAB4+JYLjjdo_nmwPqWTmd9YFk=4x4AVcprr-b7LoEc9JDqGthQ@mail.gmail.com>
Date:	Fri, 14 Oct 2011 12:52:19 -0400
From:	Godmar Back <godmar@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: Q.: Why does tty_ioctl.c: set_termios return EINTR instead of ERESTARTSYS?

A student in my OS class noticed during their shell assignment that
tcsetattr() is being interrupted with EINTR even though they had set
SA_RESTART.

Upon taking a closer look, I noticed that
drivers/char/tty_ioctl.c:set_termios(), which lies on the code path
for the POSIX tcsetattr() function, returns -EINTR when a signal is
pending. Consequently, the SA_RESTART flag is not honored and user
code must check for and handle EINTR.

I don't immediately see what would prevent this system call from being
restartable.

Is there a particular reason why it cannot be made restartable?

Thank your for any insight.

 - Godmar

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