From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id C58683858D3C for ; Mon, 17 Oct 2022 22:33:28 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org C58683858D3C Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1666046008; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=y6gQipZB5dPeMNxqDo7vrhM4ul8Z/E0c7Y7GQXrx7V4=; b=YRojvd2eZi6rf3V0N6gvZRdBgCCtcOIPNXoV4Wi7im8pHnu06EpjDyxrbuBVxCpZ7e3ZtB ik0d2bnuVxFvPv18JJEXrE1z2A9dMBKYag3cJoJDNybemfoE89lTlOVQFaCow6kGPrRunN OjspN8C1Kyt+LrTmjdhFNo3z/CCLf34= Received: from mail-pf1-f198.google.com (mail-pf1-f198.google.com [209.85.210.198]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-101-YFsrgPOJOa2A9fyDgRIVMw-1; Mon, 17 Oct 2022 18:33:27 -0400 X-MC-Unique: YFsrgPOJOa2A9fyDgRIVMw-1 Received: by mail-pf1-f198.google.com with SMTP id a11-20020a056a001d0b00b005635c581a24so6815220pfx.17 for ; Mon, 17 Oct 2022 15:33:27 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=y6gQipZB5dPeMNxqDo7vrhM4ul8Z/E0c7Y7GQXrx7V4=; b=vczqKVrRLyxN0Du8bG7XLnOAeY00Que7NEx5fRszNXLpShgw9Ew38obxzED38wmyTQ fuwzY/RzO4BvYOLVLlvtJBl2LiSockyo13acNiHEO3Ggc+uhNg8hSJCOMQvlwiJEccs5 K4HwjkVq2Moeo3Zwj0KRpRcfeFBTQOHdOzP5bVBfNbgN5B64qbCqr178tnk5da02xzi2 rvK4xhlQpwwrMblP1Drvc4GKv51jHMhrJ6zaVoICsk0+9mRRDPATanl03UehGqtyoUen p3R3hAvNbfHyq9Wu/nYFqaUNlELeyFIi4z/fsxebhGWWp6L8r5NpghLqrFgcwJZsDDjB yjFw== X-Gm-Message-State: ACrzQf0zRLsHiUdh54u2wApJAEX92CELNwvrqmvybod4uwVO2vzhCg7J 6D98i2DK0yfjXu/9tMl1OWfrf3gzjkr6OXTswijeXn0vy2UdtVuoV0t7MihQQ1AyjRjp6pOdHWw 3gzcj/IIRd7j0aZNJED6wzDMg77IOPjoUmcbb X-Received: by 2002:a62:2983:0:b0:54e:7cd5:adb3 with SMTP id p125-20020a622983000000b0054e7cd5adb3mr33313pfp.38.1666046004590; Mon, 17 Oct 2022 15:33:24 -0700 (PDT) X-Google-Smtp-Source: AMsMyM6Mtd3MHza2vrwm0MtbhFSBfHb5A7zZKQCuQZUypZlPfWTs5YtGGJuzBk3uYoy5VpbjP1qhv4Y3J9m/sKV2ARE= X-Received: by 2002:a62:2983:0:b0:54e:7cd5:adb3 with SMTP id p125-20020a622983000000b0054e7cd5adb3mr33286pfp.38.1666046004229; Mon, 17 Oct 2022 15:33:24 -0700 (PDT) MIME-Version: 1.0 References: <20220830120802.1072466-1-adhemerval.zanella@linaro.org> In-Reply-To: <20220830120802.1072466-1-adhemerval.zanella@linaro.org> From: Arjun Shankar Date: Tue, 18 Oct 2022 00:33:13 +0200 Message-ID: Subject: Re: [PATCH v2] linux: Avoid shifting a negative signed on POSIX timer interface To: Adhemerval Zanella Cc: libc-alpha@sourceware.org X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-11.8 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE,TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Hi Adhemerval, > The current macros uses pid as signed value, which triggers a compiler > warning for process and thread timers. Replace MAKE_PROCESS_CPUCLOCK > with static inline function that expects the pid as unsigned. These > are similar to what Linux does internally. > > Checked on x86_64-linux-gnu. I tried building master with -Wshift-negative-value and ran into a couple of other left-shifts on negative values in sysdeps/x86/dl-cacheinfo.h: > count_mask = ~(-1 << (count_mask + 1)); Perhaps a cast of the -1 to unsigned here would make the intent even more clear, and get glibc building cleanly with -Wshift-negative-value. What do you think? Anyway, this patch itself looks good to me. Reviewed-by: Arjun Shankar > nptl/pthread_getcpuclockid.c | 2 +- > sysdeps/unix/sysv/linux/clock_getcpuclockid.c | 2 +- > sysdeps/unix/sysv/linux/clock_nanosleep.c | 2 +- > .../unix/sysv/linux/kernel-posix-cpu-timers.h | 28 +++++++++++++++---- > sysdeps/unix/sysv/linux/timer_create.c | 4 +-- > 5 files changed, 28 insertions(+), 10 deletions(-) > > diff --git a/nptl/pthread_getcpuclockid.c b/nptl/pthread_getcpuclockid.c > index 344bd6560e..b8bf09f550 100644 > --- a/nptl/pthread_getcpuclockid.c > +++ b/nptl/pthread_getcpuclockid.c > @@ -35,7 +35,7 @@ __pthread_getcpuclockid (pthread_t threadid, clockid_t *clockid) > > /* The clockid_t value is a simple computation from the TID. */ > > - const clockid_t tidclock = MAKE_THREAD_CPUCLOCK (pd->tid, CPUCLOCK_SCHED); > + const clockid_t tidclock = make_thread_cpuclock (pd->tid, CPUCLOCK_SCHED); > > *clockid = tidclock; > return 0; OK. Use the new function instead of the old macro. > diff --git a/sysdeps/unix/sysv/linux/clock_getcpuclockid.c b/sysdeps/unix/sysv/linux/clock_getcpuclockid.c > index 5534127ed7..355d3c86af 100644 > --- a/sysdeps/unix/sysv/linux/clock_getcpuclockid.c > +++ b/sysdeps/unix/sysv/linux/clock_getcpuclockid.c > @@ -29,7 +29,7 @@ __clock_getcpuclockid (pid_t pid, clockid_t *clock_id) > /* The clockid_t value is a simple computation from the PID. > But we do a clock_getres call to validate it. */ > > - const clockid_t pidclock = MAKE_PROCESS_CPUCLOCK (pid, CPUCLOCK_SCHED); > + const clockid_t pidclock = make_process_cpuclock (pid, CPUCLOCK_SCHED); > > #ifndef __NR_clock_getres_time64 > # define __NR_clock_getres_time64 __NR_clock_getres OK. Same. > diff --git a/sysdeps/unix/sysv/linux/clock_nanosleep.c b/sysdeps/unix/sysv/linux/clock_nanosleep.c > index befe6ecb8c..e610fd4e8d 100644 > --- a/sysdeps/unix/sysv/linux/clock_nanosleep.c > +++ b/sysdeps/unix/sysv/linux/clock_nanosleep.c > @@ -34,7 +34,7 @@ __clock_nanosleep_time64 (clockid_t clock_id, int flags, > if (clock_id == CLOCK_THREAD_CPUTIME_ID) > return EINVAL; > if (clock_id == CLOCK_PROCESS_CPUTIME_ID) > - clock_id = MAKE_PROCESS_CPUCLOCK (0, CPUCLOCK_SCHED); > + clock_id = PROCESS_CLOCK; > > /* If the call is interrupted by a signal handler or encounters an error, > it returns a positive value similar to errno. */ OK. PROCESS_CLOCK expands to the appropriate call to make_process_cpuclock. > diff --git a/sysdeps/unix/sysv/linux/kernel-posix-cpu-timers.h b/sysdeps/unix/sysv/linux/kernel-posix-cpu-timers.h > index 164a90ddeb..bea1e0e62d 100644 > --- a/sysdeps/unix/sysv/linux/kernel-posix-cpu-timers.h > +++ b/sysdeps/unix/sysv/linux/kernel-posix-cpu-timers.h > @@ -1,4 +1,12 @@ > -/* Parameters for the Linux kernel ABI for CPU clocks. */ > +/* > + Parameters for the Linux kernel ABI for CPU clocks, the bit fields within > + a clockid: > + > + - The most significant 29 bits hold either a pid or a file descriptor. > + - Bit 2 indicates whether a cpu clock refers to a thread or a process. > + - Bits 1 and 0 give the type: PROF=0, VIRT=1, SCHED=2, or FD=3. > + - A clockid is invalid if bits 2, 1, and 0 are all set. > + */ > > #define CPUCLOCK_PID(clock) ((pid_t) ~((clock) >> 3)) > #define CPUCLOCK_PERTHREAD(clock) \ OK. Comment lines up with the one in Linux's "include/linux/posix-timers.h". > @@ -12,7 +20,17 @@ > #define CPUCLOCK_SCHED 2 > #define CPUCLOCK_MAX 3 > > -#define MAKE_PROCESS_CPUCLOCK(pid, clock) \ > - ((~(clockid_t) (pid) << 3) | (clockid_t) (clock)) OK. clockid_t is a signed type, thus expanding with pid = 0 leads to a left-shift on a negative value. > -#define MAKE_THREAD_CPUCLOCK(tid, clock) \ > - MAKE_PROCESS_CPUCLOCK((tid), (clock) | CPUCLOCK_PERTHREAD_MASK) OK. Same macro used. Same issue. > +static inline clockid_t > +make_process_cpuclock (unsigned int pid, clockid_t clock) > +{ > + return ((~pid) << 3) | clock; > +} > + OK. Replacement function that uses unsigned. Lines up with the version in Linux's sources. > +static inline clockid_t > +make_thread_cpuclock (unsigned int tid, clockid_t clock) > +{ > + return make_process_cpuclock (tid, clock | CPUCLOCK_PERTHREAD_MASK); > +} > + OK. Replaces the second macro for tid. > +#define PROCESS_CLOCK make_process_cpuclock (0, CPUCLOCK_SCHED) > +#define THREAD_CLOCK make_thread_cpuclock (0, CPUCLOCK_SCHED) OK. Macros for convenience. > diff --git a/sysdeps/unix/sysv/linux/timer_create.c b/sysdeps/unix/sysv/linux/timer_create.c > index a8b2a41d9e..290324a7ea 100644 > --- a/sysdeps/unix/sysv/linux/timer_create.c > +++ b/sysdeps/unix/sysv/linux/timer_create.c > @@ -33,9 +33,9 @@ ___timer_create (clockid_t clock_id, struct sigevent *evp, timer_t *timerid) > { > { > clockid_t syscall_clockid = (clock_id == CLOCK_PROCESS_CPUTIME_ID > - ? MAKE_PROCESS_CPUCLOCK (0, CPUCLOCK_SCHED) > + ? PROCESS_CLOCK > : clock_id == CLOCK_THREAD_CPUTIME_ID > - ? MAKE_THREAD_CPUCLOCK (0, CPUCLOCK_SCHED) > + ? THREAD_CLOCK > : clock_id); > > /* If the user wants notification via a thread we need to handle OK. Use the new macros.