Hello Heinrich, On 02/17/2015 03:06 PM, Heinrich Schuchardt wrote: > The futex.2 system call makes no assumption about the meaning > of the values of a futex. > It may check if the value changes. > > The current futex.7 speaks of incrementing and decrementing > a futex. That choice is arbitrary and unwise as overflows may > occur. > > If special considerations for the usage of futex.2 have to be made > in a futex.7 example, this should be explained in futex.7 A recent patch by Torvald Riegel also proposed many of the same changes, and I've applied that patch. Oone piece was not quite covered by Torvald's patch see my comment below. > Signed-off-by: Heinrich Schuchardt <xypron.glpk@xxxxxx> > --- > man2/futex.2 | 33 +-------------------------------- > 1 file changed, 1 insertion(+), 32 deletions(-) > > diff --git a/man2/futex.2 b/man2/futex.2 > index 6c02da7..0ea7db2 100644 > --- a/man2/futex.2 > +++ b/man2/futex.2 > @@ -68,16 +68,6 @@ When a futex operation did not finish uncontended in user space, a > call needs to be made to the kernel to arbitrate. > Arbitration can either mean putting the caller > to sleep or, conversely, waking a waiting process or thread. > -.PP > -Callers of > -.BR futex () > -are expected to adhere to the semantics described in > -.BR futex (7). > -As these semantics involve writing nonportable assembly instructions > -(see the example library referred to in SEE ALSO), > -this in turn probably means that most users will in fact be > -library authors and not general application developers. > -.\" > .SS Arguments > The > .I uaddr > @@ -229,18 +219,6 @@ The arguments > and > .I val3 > are ignored. > - > -For > -.BR futex (7), > -this call is executed if decrementing the count gave a negative value > -(indicating contention), > -and will sleep until another process or thread releases > -the futex and executes the > -.B FUTEX_WAKE > -operation. > -.\" > -.\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" > -.\" > .TP > .BR FUTEX_WAKE " (since Linux 2.6.0)" > .\" Strictly speaking, since Linux 2.5.x > @@ -266,15 +244,6 @@ The arguments > and > .I val3 > are ignored. > - > -For > -.BR futex (7), > -this is executed if incrementing the count showed that there were waiters, > -.\" FIXME How does "incrementing the count showed that there were waiters"? > -once the futex value has been set to 1 (indicating that it is available). > -.\" > -.\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" > -.\" > .TP > .BR FUTEX_FD " (from Linux 2.6.0 up to and including Linux 2.6.25)" > .\" Strictly speaking, from Linux 2.5.x to 2.6.25 > @@ -304,7 +273,7 @@ and > are ignored. > > To prevent race conditions, the caller should test if the futex has > -been upped after > +been changed after Torvald also questioned this sentence; currently it has a FIXME asking whether maybe it should just be removed altogether. Thanks, Michael > .B FUTEX_FD > returns. > > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
