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Auto merge of #4416 - daira:sa_restart, r=daira 

Use SA_RESTART in sa_flags when setting up signal handlers

Explanation: if a signal interrupts certain syscalls such as `open`, `read`, or `write`,
then the library function will by default fail with `errno` `EINTR`. But we [almost](https://github.com/zcash/zcash/search?q=WSAEINTR) [never](https://github.com/zcash/zcash/search?q=EINTR)
check for `EINTR`, so this is likely to cause spurious errors. We want to restart the syscall
instead, which is what `SA_RESTART` is intended to do. Since our signal handlers (defined
in init.cpp) only set a flag, restarting the syscall is safe and is always the Right Thing.

See <https://www.gnu.org/software/libc/manual/html_node/Flags-for-Sigaction.html> and
<https://www.gnu.org/software/libc/manual/html_node/Interrupted-Primitives.html> for
further information.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
This commit is contained in:
Homu 2020-04-15 19:23:14 +00:00
parent 1f5de9cae2 dd215e8994
commit 4fad49d802
1 changed files with 2 additions and 2 deletions
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4
src/init.cpp
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@ -874,7 +874,7 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
struct sigaction sa;
sa.sa_handler = HandleSIGTERM;
sigemptyset(&sa.sa_mask);
sa.sa_flags = 0;
sa.sa_flags = SA_RESTART;
sigaction(SIGTERM, &sa, NULL);
sigaction(SIGINT, &sa, NULL);
@ -883,7 +883,7 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
struct sigaction sa_hup;
sa_hup.sa_handler = HandleSIGHUP;
sigemptyset(&sa_hup.sa_mask);
sa_hup.sa_flags = 0;
sa_hup.sa_flags = SA_RESTART;
sigaction(SIGHUP, &sa_hup, NULL);
// Ignore SIGPIPE, otherwise it will bring the daemon down if the client closes unexpectedly