Rich Felker
b470030f83
this commit addresses two issues: 1. a race condition, whereby a cancellation request occurring after a syscall returned from kernelspace but before the subsequent CANCELPT_END would cause cancellable resource-allocating syscalls (like open) to leak resources. 2. signal handlers invoked while the thread was blocked at a cancellation point behaved as if asynchronous cancellation mode wer in effect, resulting in potentially dangerous state corruption if a cancellation request occurs. the glibc/nptl implementation of threads shares both of these issues. with this commit, both are fixed. however, cancellation points encountered in a signal handler will not be acted upon if the signal was received while the thread was already at a cancellation point. they will of course be acted upon after the signal handler returns, so in real-world usage where signal handlers quickly return, it should not be a problem. it's possible to solve this problem too by having sigaction() wrap all signal handlers with a function that uses a pthread_cleanup handler to catch cancellation, patch up the saved context, and return into the cancellable function that will catch and act upon the cancellation. however that would be a lot of complexity for minimal if any benefit...
17 lines
400 B
C
17 lines
400 B
C
#include <sys/select.h>
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#include "syscall.h"
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#include "libc.h"
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int pselect(int n, fd_set *rfds, fd_set *wfds, fd_set *efds, const struct timespec *ts, const sigset_t *mask)
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{
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int r;
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long data[2] = { (long)mask, 8 };
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struct timespec ts_tmp;
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if (ts) ts_tmp = *ts;
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CANCELPT_BEGIN;
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r = syscall(SYS_pselect6, n, rfds, wfds, efds, ts ? &ts_tmp : 0, data);
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CANCELPT_TRY;
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CANCELPT_END;
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return r;
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}
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