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bh=C6f4WmUv/27EpEn0x2H5yv5+cCWHN1evpHYPC1oYxaM=; b=cPHdZN98wbKn8IIKT5nFcBaFkhoWG8+nKcZu1gQJnO5i9mIRH1urx/JIg9YZVrOuFp MW7V77xySbbfAz0eKwY6E9G+P0tkGNGxQE8Tq6jl0bUM/jDrM7dfzGbLG6/j/3bu5gDK fAbvBRmtI0mnoBXQq/RfL0KbkvFQBdtCjf5jOLWnBygHq2TzjqbUj2Cc66xYBqqMt+Ir k+XjHrY3Ais1gMKYwj3u2tccHlg+4H6boJwKj9dwaB4nsN/TTkRThR0xvOX8+y3lQfRM SHCfnqu7Bi3oPReyvBYvj3kdbsTPK7qKgYm2aGvpjP9Z7mLhvPSauLbChmEPdHtHPTKD +x0g== X-Gm-Message-State: ALQs6tAW1YSWLHYuZsTzrWdh53cI1p8MtifFvSC+gJG7LarJoe0W8a4x dP98gpLli30GEmXFIw6p1ART7rMkNic= X-Google-Smtp-Source: AB8JxZqiyuzFbBuehgfNh4RyerNYNV4qhnNk0bXk2Hejs2vPZkPm2V3adoeshcqwOxNqQv8JllIUvQ== X-Received: by 10.55.197.88 with SMTP id p85mr34512549qki.221.1525802219562; Tue, 08 May 2018 10:56:59 -0700 (PDT) Subject: Re: [PATCH v2 06/21] nptl: i386: Fix Race conditions in pthread cancellation (BZ#12683) To: Zack Weinberg , libc-alpha@sourceware.org References: <20180507024909.5598-1-zackw@panix.com> <20180507024909.5598-5-zackw@panix.com> From: Adhemerval Zanella Openpgp: preference=signencrypt Autocrypt: addr=adhemerval.zanella@linaro.org; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180507024909.5598-5-zackw@panix.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit On 06/05/2018 23:49, Zack Weinberg wrote: > On 26 Feb 2018, Adhemerval Zanella wrote: >> This patch adds the i386 modifications required for the BZ#12683. >> It basically provides the required ucontext_get_pc symbol, add the >> cancelable syscall wrapper and fix a thread atomic update macro. > > This also seems fine. > >> On i386 an arch-specific cancellation implementation is required >> because depending of the glibc configuration and underlying kernel >> the syscall may be done using a vDSO symbol (__kernel_vsyscall). > ... >> Also, since glibc supports i486, the old 'int 0x80' should be used >> in the syscall wrapper. One option could make minimum default chip >> to pentium II (which implements sysenter) or add a runtime check >> on syscall_cancel.S to use 'int 0x80' or sysenter. > > If I remember correctly, there can be only one 'sysenter' instruction > in the entire user address space, due to awkward limitations of the > interface it presents to the kernel. That was why __kernel_vsyscall > was added in the first place. > > We can probably live with using int 0x80 for these syscalls that may > well be blocking anyway. > >> Similar to x86_64, it also remove bogus arch-specific >> THREAD_ATOMIC_BIT_SET where it always reference to current thread >> instead of the one referenced by input 'descr' argument. > > Same comment as for x86_64 -- shouldn't we get rid of or repair _all_ of > the THREAD_ATOMIC_ macros that don't honor their arguments? > > zw > Alright, I will remove then in an extra patch as well.