From 064ea89caa3d8b2183ad5827ee124c1213286e0c Mon Sep 17 00:00:00 2001 From: cinap_lenrek Date: Sun, 18 Nov 2018 03:37:04 +0100 Subject: libdraw: avoid deadlock for mouse ioproc sending on resizec a deadlock has been observed with samterm (thanks burnzez), that shows the mouse ioproc being stuck in sending on the resize channel, while the mouse consumer is stuck in a readmouse() loop wanting a rectangle to be drawn by the user: recv(v=0x42df50)+0x28 /sys/src/libthread/channel.c:321 readmouse(mc=0x42df50)+0x54 /sys/src/libdraw/mouse.c:34 getrect(.ret=0x41bce0,but=0x4,mc=0x42df50)+0x62 /sys/src/libdraw/getrect.c:49 r=0x41bc70 rc=0x41bc70 getr(rp=0x41bce0)+0x24 /sys/src/cmd/samterm/main.c:244 p=0x6b000004f6 r=0x2 sweeptext(new=0x0,tag=0x2d)+0x12 /sys/src/cmd/samterm/menu.c:208 r=0x2 t=0x42df50 inmesg(type=0x2,count=0x2)+0x1ab /sys/src/cmd/samterm/mesg.c:136 m=0x10000002d l=0x2d00001b00 i=0x43829000000001 t=0x438290 lp=0x42e050 rcv()+0x7a /sys/src/cmd/samterm/mesg.c:77 threadmain(argv=0x7ffffeffef90)+0x173 /sys/src/cmd/samterm/main.c:63 so avoid blocking in the mouse ioproc by using nbsend() instead of send() for writing to the resize channel. --- sys/src/libdraw/mouse.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'sys/src/libdraw/mouse.c') diff --git a/sys/src/libdraw/mouse.c b/sys/src/libdraw/mouse.c index 984ae3350..3ae6d5cc7 100644 --- a/sys/src/libdraw/mouse.c +++ b/sys/src/libdraw/mouse.c @@ -66,7 +66,7 @@ _ioproc(void *arg) switch(buf[0]){ case 'r': one = 1; - if(send(mc->resizec, &one) < 0) + if(nbsend(mc->resizec, &one) < 0) continue; /* fall through */ case 'm': @@ -122,7 +122,7 @@ initmouse(char *file, Image *i) free(t); mc->image = i; mc->c = chancreate(sizeof(Mouse), 0); - mc->resizec = chancreate(sizeof(int), 2); + mc->resizec = chancreate(sizeof(int), 1); mc->pid = proccreate(_ioproc, mc, 4096); return mc; } -- cgit v1.2.3