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nptl: Fix racy pipe closing in tst-cancel{20,21}
The tst-cancel20 open two pipes and creates a thread which blocks reading the first pipe. It then issues a signal to activate the signal handler which in turn blocks reading the second pipe end. Finally the cancellation cleanup-up handlers are tested by first closing the all the pipes ends and issuing a pthread_cancel. The tst-cancel21 have a similar behavior, but use an extra fork after the test itself. The race condition occurs if the cancellation handling acts after the pipe close: in this case read will return EOF (indicating side-effects) and thus the cancellation must not act. However current GLIBC cancellation behavior acts regardless the syscalls returns with sid-effects. This patch adjust the test by moving the pipe closing after the cancellation handling. This avoid spurious cancellation if the case of the race described. Checked on x86_64 and i386. * nptl/tst-cancel20.c (do_one_test): Move the pipe closing after pthread_join. * nptl/tst-cancel21.c (tf): Likewise.
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@ -1,3 +1,9 @@
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2015-12-02 Adhemerval Zanella <adhemerval.zanella@linaro.org>
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* nptl/tst-cancel20.c (do_one_test): Move the pipe closing after
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pthread_join.
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* nptl/tst-cancel21.c (tf): Likewise.
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2015-12-01 H.J. Lu <hongjiu.lu@intel.com>
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[BZ #19313]
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@ -145,12 +145,6 @@ do_one_test (void)
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return 1;
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}
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/* This will cause the read in the child to return. */
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close (fd[0]);
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close (fd[1]);
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close (fd[2]);
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close (fd[3]);
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void *ret;
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if (pthread_join (th, &ret) != 0)
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{
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@ -170,6 +164,15 @@ do_one_test (void)
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return 1;
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}
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/* The pipe closing must be issued after the cancellation handling to avoid
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a race condition where the cancellation runs after both pipe ends are
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closed. In this case the read syscall returns EOF and the cancellation
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must not act. */
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close (fd[0]);
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close (fd[1]);
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close (fd[2]);
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close (fd[3]);
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return 0;
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}
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@ -123,12 +123,6 @@ tf (void *arg)
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exit (1);
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}
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/* This will cause the read in the initial thread to return. */
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close (fd[0]);
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close (fd[1]);
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close (fd[2]);
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close (fd[3]);
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void *ret;
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if (pthread_join (th, &ret) != 0)
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{
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@ -154,6 +148,15 @@ tf (void *arg)
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exit (1);
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}
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/* The pipe closing must be issued after the cancellation handling to avoid
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a race condition where the cancellation runs after both pipe ends are
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closed. In this case the read syscall returns EOF and the cancellation
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must not act. */
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close (fd[0]);
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close (fd[1]);
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close (fd[2]);
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close (fd[3]);
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exit (0);
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}
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