From owner-freebsd-arch  Sat Feb 16 10:42:19 2002
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Date: Sat, 16 Feb 2002 10:42:15 -0800 (PST)
From: Matthew Dillon <dillon@apollo.backplane.com>
Message-Id: <200202161842.g1GIgFF89658@apollo.backplane.com>
To: Peter Wemm <peter@wemm.org>
Cc: Dan Eischen <eischen@vigrid.com>, arch@FreeBSD.ORG
Subject: MFC makecontext(), getcontext(), setcontext()?, also would be nice to have some cleanups
References:  <20020206195918.6350039F1@overcee.wemm.org>
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X-Loop: FreeBSD.ORG

    It would be nice if getcontext() and setcontext() could be told
    not to screw around with the signal mask, similar to what sigsetjmp()
    and siglongjmp() do if the savemask is empty.  Perhaps something like
    this:

    BEFORE:

2:      PIC_PROLOGUE
        pushl   $0                      /* oset = NULL */
        pushl   %eax                    /* set = &ucp->uc_sigmask */
        pushl   $3                      /* how = SIG_SETMASK */
        call    PIC_PLT(CNAME(_sigprocmask))
        addl    $12, %esp
        PIC_EPILOGUE

    AFTER:

2:      PIC_PROLOGUE
	testl	(%eax)		<<<<<<<<<<< ADD
	jz	21f		<<<<<<<<<<< ADD
        pushl   $0                      /* oset = NULL */
        pushl   %eax                    /* set = &ucp->uc_sigmask */
        pushl   $3                      /* how = SIG_SETMASK */
        call    PIC_PLT(CNAME(_sigprocmask))
        addl    $12, %esp
        PIC_EPILOGUE
	testl	%eax,%eax
	jnz	5f
21:				<<<<<<<<<<< ADD

    (make same change in both setcontext() and getcontext())

    This way these calls could be used to replace the alternate signal
    stack, sigsetjmp()/setlongjmp() junk that has to be done now in
    roll-your-own threads systems.

    Any objections to me doing this?

    I would also like to MFC these functions to -stable at some point.

						-Matt


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