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([2001:a61:245a:d801:2e74:88ad:ef9:5218]) by smtp.gmail.com with ESMTPSA id e2sm12474935wrr.85.2020.10.30.12.19.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 30 Oct 2020 12:19:26 -0700 (PDT) Cc: mtk.manpages@gmail.com, linux-man@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] futex.2: Use appropriate types To: Alejandro Colomar References: <20201030123956.36169-1-colomar.6.4.3@gmail.com> <20201030123956.36169-2-colomar.6.4.3@gmail.com> From: "Michael Kerrisk (man-pages)" Message-ID: Date: Fri, 30 Oct 2020 20:19:26 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1 MIME-Version: 1.0 In-Reply-To: <20201030123956.36169-2-colomar.6.4.3@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/30/20 1:39 PM, Alejandro Colomar wrote: > The Linux kernel uses the following: > > kernel/futex.c:3778: > SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val, > struct __kernel_timespec __user *, utime, u32 __user *, uaddr2, > u32, val3) > > Since there is no glibc wrapper, use the same types the kernel uses. Thanks. Patch applied. Cheers, Michael > Signed-off-by: Alejandro Colomar > --- > man2/futex.2 | 27 ++++++++++++++------------- > 1 file changed, 14 insertions(+), 13 deletions(-) > > diff --git a/man2/futex.2 b/man2/futex.2 > index 837adbd25..73de71623 100644 > --- a/man2/futex.2 > +++ b/man2/futex.2 > @@ -26,12 +26,13 @@ futex \- fast user-space locking > .nf > .PP > .B #include > +.B #include > .B #include > .PP > -.BI "int futex(int *" uaddr ", int " futex_op ", int " val , > +.BI "long futex(uint32_t *" uaddr ", int " futex_op ", uint32_t " val , > .BI " const struct timespec *" timeout , \ > " \fR /* or: \fBuint32_t \fIval2\fP */" > -.BI " int *" uaddr2 ", int " val3 ); > +.BI " uint32_t *" uaddr2 ", uint32_t " val3 ); > .fi > .PP > .IR Note : > @@ -581,8 +582,8 @@ any of the two supplied futex words: > .IP > .in +4n > .EX > -int oldval = *(int *) uaddr2; > -*(int *) uaddr2 = oldval \fIop\fP \fIoparg\fP; > +uint32_t oldval = *(uint32_t *) uaddr2; > +*(uint32_t *) uaddr2 = oldval \fIop\fP \fIoparg\fP; > futex(uaddr, FUTEX_WAKE, val, 0, 0, 0); > if (oldval \fIcmp\fP \fIcmparg\fP) > futex(uaddr2, FUTEX_WAKE, val2, 0, 0, 0); > @@ -1765,11 +1766,11 @@ Child (18535) 4 > #define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \e > } while (0) > > -static int *futex1, *futex2, *iaddr; > +static uint32_t *futex1, *futex2, *iaddr; > > static int > -futex(int *uaddr, int futex_op, int val, > - const struct timespec *timeout, int *uaddr2, int val3) > +futex(uint32_t *uaddr, int futex_op, uint32_t val, > + const struct timespec *timeout, uint32_t *uaddr2, uint32_t val3) > { > return syscall(SYS_futex, uaddr, futex_op, val, > timeout, uaddr2, val3); > @@ -1779,9 +1780,9 @@ futex(int *uaddr, int futex_op, int val, > become 1, and then set the value to 0. */ > > static void > -fwait(int *futexp) > +fwait(uint32_t *futexp) > { > - int s; > + long s; > > /* atomic_compare_exchange_strong(ptr, oldval, newval) > atomically performs the equivalent of: > @@ -1794,7 +1795,7 @@ fwait(int *futexp) > while (1) { > > /* Is the futex available? */ > - const int one = 1; > + const uint32_t one = 1; > if (atomic_compare_exchange_strong(futexp, &one, 0)) > break; /* Yes */ > > @@ -1811,13 +1812,13 @@ fwait(int *futexp) > so that if the peer is blocked in fpost(), it can proceed. */ > > static void > -fpost(int *futexp) > +fpost(uint32_t *futexp) > { > - int s; > + long s; > > /* atomic_compare_exchange_strong() was described in comments above */ > > - const int zero = 0; > + const uint32_t zero = 0; > if (atomic_compare_exchange_strong(futexp, &zero, 1)) { > s = futex(futexp, FUTEX_WAKE, 1, NULL, NULL, 0); > if (s == \-1) > -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/