[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH 0/6] tools/libxs: Fix SIGPIPE handling issues
On 18.07.2024 18:48, Andrew Cooper wrote: > While the purpose of this series is patch 6, it has a side effect of reducing > the number of system calls substantally. > > Using a strace of test-xenstore as an example, we go from this: > > rt_sigaction(SIGPIPE, {sa_handler=SIG_IGN, sa_mask=[], > sa_flags=SA_RESTORER, sa_restorer=0x7fda8278e2f0}, {sa_handler=SIG_DFL, > sa_mask=[], sa_flags=SA_RESTORER, sa_restorer=0x7fda8278e2f0}, 8) = 0 > write(3, "\v\0\0\0\0\0\0\0\0\0\0\0\30\0\0\0", 16) = 16 > write(3, "xenstore-test/502673/a\0", 23) = 23 > write(3, "a", 1) = 1 > read(3, "\v\0\0\0\0\0\0\0\0\0\0\0\3\0\0\0", 16) = 16 > read(3, "OK\0", 3) = 3 > rt_sigaction(SIGPIPE, {sa_handler=SIG_DFL, sa_mask=[], > sa_flags=SA_RESTORER, sa_restorer=0x7fda8278e2f0}, NULL, 8) = 0 > > down to this: > > sendmsg(3, {msg_name=NULL, msg_namelen=0, > msg_iov=[{iov_base="\v\0\0\0\0\0\0\0\0\0\0\0\30\0\0\0", iov_len=16}, > {iov_base="xenstore-test/504021/a\0", iov_len=23}, {iov_base="a", > iov_len=1}], msg_iovlen=3, msg_controllen=0, msg_flags=0}, MSG_NOSIGNAL) = 40 > read(3, "\v\0\0\0\0\0\0\0\0\0\0\0\3\0\0\0", 16) = 16 > read(3, "OK\0", 3) = 3 > > > I.e., it removes 2x rt_sigaction(), and turns all write()'s into a single > writev() or sendmsg(). > > > Reads are a little more problematic to deal with. Xenstored will produce a > full package basically in one go, but libxenstore's reading is horrbly > complicated by virtue of it being completely different depending on whether > xs_watch() has created a secondary read thread or not. > > Andrew Cooper (6): > tools/libxs: Fix length check in xs_talkv() > tools/libxs: Rework xs_talkv() to take xsd_sockmsg within the iovec > tools/libxs: Rationalise the definition of struct xs_handle > tools/libxs: Track whether we're using a socket or file > tools/libxs: Use writev()/sendmsg() instead of write() > tools/libxs: Stop playing with SIGPIPE The title of the entire series containing "Fix" vs there being no single Fixes: tag throughout, afaics, leave unclear to me whether any or all of this work wants/needs backporting. Please clarify. Jan
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